Manganese dioxide decorated kiwi peel powder for efficient removal of lead from aqueous solutions, blood and Traditional Chinese Medicine extracts

For human health and environment safety, it is of great significance to develop novel materials with high effectiveness for removal of lead from not only aqueous solutions but also human body and traditional Chinese medicines. Here, functional kiwi peel composite, manganese dioxide decorated kiwi peel powder (MKPP), is proposed for the removal of Pb2+ effectively. The adsorption of Pb2+ in aqueous solution is a highly selective and endothermic process and kinetically follows a pseudo-second-order model, which can reach equilibrium with the capacity of 192.7 mg/g within 10 min. Comprehensive factors of hydration energy, charge-to-radius ratio and softness of Pb2+ make a stronger affinity between MKPP and Pb2+. The possible adsorption mechanism involves covalent bond, electrostatic force and chelation, etc. MKPP can be efficiently regenerated and reused with high adsorption efficiency after five cycles. Besides, MKPP can remove over 97% of Pb2+ from real water samples. MKPP can also alleviate lead poisoning to a certain extent and make the Pb level of TCM extract meet the safety standard. This work highlights that MKPP is a promising adsorbent for the removal of Pb2+ and provides an efficient strategy for reusing kiwi peel as well as dealing with the problem of Pb pollution.

Estimation of sorption-desorption characteristics of biosorbent of Lantana camara leaves for removal of Pb (II) ions from wastewater

This study points out the method regarding the removal of Pb (II) ions from water by treatment with Lantana camara leaves' biosorbent (LCLB). The sorption process was investigated by varying different parameters pH, contact time, adsorbent dose, initial metal ion concentration, and temperature. For a 5.00 g sorbent dose and a 45 min of the contact period, a Pb (II) ion solution with an initial metal ion concentration of 10 mg/L resulted in 90.7% maximum elimination at an optimum pH 6 and temperature 298 ± 1.5 K with LCLB. The adsorption process was spontaneous and exothermic. The maximum monolayer adsorption was 3.5 mg/g for Pb (II) sorption using LCLB. Adsorption of Pb (II) ions using LCLB (R² > 0.999) followed the pseudo-second-order kinetics. The spectroscopic characterization was done by fourier transform infrared (FT-IR) analysis, while scanning electron microscope (SEM) images were captured for the morphological characterization. Desorption experiments revealed that hydrochloric acid has a strong potential as an eluent for Pb (II) ion desorption. The findings proposed that LCLB can be used as an effectual and cost-effective biosorbent for the expulsion of Pb (II) ions.

Green synthesis, characterization of Radix Hedysari-mediated silver nanoparticles and their use for sensitive colorimetric detection of Pb2+ in the Yellow River medium

In this study, a safe, rapid, and environment-friendly green synthesis of silver nanoparticles using the alcohol extract of Radix Hedysari (RH-AgNPs) was developed, the alcohol extract of Radix Hedysari (RH) acted as the reducing agent, stabilizer, and modifier. The main components of RH were determined using high-performance liquid chromatography (HPLC). The particle size and morphology of RH-AgNPs were optimized and characterized by a series of techniques. The size distribution, zeta potential, element distribution, and crystalline nature of RH-AgNPs were all determined. It was indicated that RH-AgNPs showed great sensitivity for lead ion (Pb²⁺) detection with a limit of detection (LOD) of 1.5 μM with a wide range of 10-500 μM. The selectivity was also explored for common metal ions. RH-AgNPs were then applied to the detection of Pb²⁺ in spiked Yellow River samples, and the possible mechanism is based on the crosslinking reaction between the hydroxide radical, carboxylate radical and Pb²⁺.

Simultaneous Efficient Decontamination of Bacteria and Heavy Metals via Capacitive Deionization Using Polydopamine/Polyhexamethylene Guanidine Co-deposited Activated Carbon Electrodes

The contamination of pathogenic micro-organisms and heavy metals in drinking water sources poses a serious threat to human health, which raises the demand for efficient water treatments. Herein, multi-functional capacitive deionization (CDI) electrodes were developed for the simultaneous decontamination of bacteria and heavy metal contaminants. Polyhexamethylene guanidine (PHMG), an antibacterial polymer, was deposited on the surface of the activated carbon (AC) electrode with the assistance of mussel-inspired polydopamine (PDA) chemistry. The main characterization results proved successful co-deposition of PDA and PHMG on the AC electrode, forming a hydrophilic coating layer in one step. Electrochemical analyses indicated that the AC-PDA/PHMG electrodes presented satisfactory capacitive behaviors, with outstanding salt adsorption capacity and cycling stability. The modified electrodes also exhibit excellent disinfection performance and heavy metal adsorption performance. The bacterial elimination rate of co-deposited electrodes grew along with the increase in the PHMG content. Particularly, AC-PDA/PHMG₂ electrodes successfully removed and deactivated 99.11% Escherichia coli and 98.67% Pseudomonas aeruginosa (10⁴ CFU mL^-1) in water within 60 min. Furthermore, three flow cells made by AC-PDA/PHMG₂ electrodes connected in series achieved efficient removal of salt, heavy metals such as lead and cadmium, and bacteria simultaneously, which indicated that the adsorption performance is significantly improved compared with pristine AC electrodes. These results denote the enormous potential of this one-step prepared multi-functional electrodes for facile and effective water purification using CDI technology.

Bioinspired Neuron-like Adsorptive Networks for Heavy Metal Capture and Tunable Electrochemically Mediated Recovery

Electrochemical techniques have garnered increasing attention as a heavy metal remediation platform for pollutant mitigation and sustainable recycling. Inspired by the biological signal-transfer mode, biomimic neuron-like hierarchical adsorptive networks were constructed by interweaving one-dimensional manganese oxide nanowires into polyaniline-decorated hollow structural metal-organic frameworks (MOFs). The prepared biomimic neuron adsorbent exhibits good adsorption capacity toward cations (Pb²⁺) and oxyanions (Cr₂O₇^2-) at the neutral state; tunable cation/oxyanion desorption can be electrochemically switched at the oxidized and reduced states, respectively, where the biomimic neuron-like hierarchical adsorptive networks facilitated electron transfer and benefited substantial redox reactions. The combination of simulations and calculations demonstrates that the curvature-induced polarization in a hollow MOF structure enhances the desorption efficiencies by improving the redox processes at the electrode-electrolyte interface, which facilitate the promising implementation in terms of water economy and downstream waste sustainability.

Highly-Efficient Sulfonated UiO-66(Zr) Optical Fiber for Rapid Detection of Trace Levels of Pb2

Lead detection for biological environments, aqueous resources, and medicinal compounds, rely mainly on either utilizing bulky lab equipment such as ICP-OES or ready-made sensors, which are based on colorimetry with some limitations including selectivity and low interference. Remote, rapid and efficient detection of heavy metals in aqueous solutions at ppm and sub-ppm levels have faced significant challenges that requires novel compounds with such ability. Here, a UiO-66(Zr) metal-organic framework (MOF) functionalized with SO3H group (SO3H-UiO-66(Zr)) is deposited on the end-face of an optical fiber to detect lead cations (Pb2+) in water at 25.2, 43.5 and 64.0 ppm levels. The SO3H-UiO-66(Zr) system provides a Fabry–Perot sensor by which the lead ions are detected rapidly (milliseconds) at 25.2 ppm aqueous solution reflecting in the wavelength shifts in interference spectrum. The proposed removal mechanism is based on the adsorption of [Pb(OH2)6]2+ in water on SO3H-UiO-66(Zr) due to a strong affinity between functionalized MOF and lead. This is the first work that advances a multi-purpose optical fiber-coated functional MOF as an on-site remote chemical sensor for rapid detection of lead cations at extremely low concentrations in an aqueous system.

Evaluation of adsorption ability of cyclodextrin-calixarene nanosponges towards Pb2+ ion in aqueous solution

Different cyclodextrin-calixarene nanosponges (CyCaNSs) have been characterized by means of FFC-NMR relaxometry, and used as sorbents to remove Pb²⁺ ions from aqueous solutions. Considering that the removal treatments may involve polluted waters with different characteristics, the adsorption experiments were performed on solutions without and with the addition of background salts, under different operational conditions. The adsorption abilities and affinities of the nanosponges towards Pb²⁺ ions were investigated by measuring the metal ion concentration by means of Inductively Coupled Plasma Emission Spectroscopy (ICP-OES) and Differential Pulse Anodic Stripping Voltammetry (DP-ASV). The acid-base properties of nanosponges and of metal ion as well as their interactions with the other interacting components of the systems have been considered in the evaluation of adsorption mechanism. Recycling and reuse experiments on the most efficient adsorbents were also performed. On the grounds of the results obtained, post-modified CyCaNSs appear promising materials for designing environmental remediation devices.

Green and efficient removal of heavy metals from Porphyra haitanensis using natural deep eutectic solvents

BACKGROUND

Porphyra haitanensis now faces serious heavy metal pollution problems. Natural deep eutectic solvents (NADESs) have been recognized as a novel class of sustainable solvents, which can be used for heavy metal removal. In this study, 28 kinds of NADESs were prepared and investigated as eluent in the removal of lead (Pb), cadmium (Cd), chromium (Cr), arsenic (As), and copper (Cu) from P. haitanensis for the first time, and the adsorption mechanism of NADESs was also studied.

RESULTS

The removals were greatly improved by NADESs compared with control where the removal rates of Pb, Cd, Cr, As and Cu were 17.4-87.54%, 57.54-100%, 9.8-48.59%, 21.32-78.24% and 11.68-79.73%, respectively. The optimal condition was 10% water content and solid-liquid ratio of 1:20. Moreover, the addition of 20% natural surfactant arabic gum can further increase the heavy metals removal rates of NADESs. The adsorption mechanism experiments showed that the pseudo second-order model and the Freundlich adsorption model can better explain the adsorption mechanism of NADESs on heavy metals removal.

CONCLUSION

Taken together, a green and efficient method for removing heavy metals from P. haitanensis was established. © 2020 Society of Chemical Industry.

Oyster shell powder for Pb(II) immobilization in both aquatic and sediment environments

Heavy metal pollution has always been a serious environmental problem widely concerned by researchers all around the world. On the other side, the accumulation of biowastes has also occupied a large amount of space and caused a series of environment pollution. In this study, the waste oyster shell, was applied as a type of biogenic carbonate material for Pb(II) removal from the aquatic environment, and further as a remediation agent for metal stabilization in the contaminated river sediment. After simple pretreatment, the oyster shell powder (OSP) was characterized, and the results showed that the prepared OSP is mainly composed of calcite with particle size of micron-level. The OSP exhibited excellent Pb(II) adsorption performance, with the adsorption capacity as 639.9 mg/g through adsorption isotherm study. Furthermore, the OSP was applied to remediate the collected river sediment artificially contaminated by Pb(II). It was found that the proportion of residual Pb fraction (F4) was greatly increased from 39.6% of the original sediment to 76.7% in the 14-day incubated sediment with OSP. The Pb(II) concentration after leaching procedure was decreased from 810.7 to 108.6 μg/L even after 5-day incubation. Therefore, this study shows the potential of using waste oyster shell as adsorbent and amendment agent for effective metal immobilization in both aquatic and sediment systems.

Copper and lead ion removal from wastewater using fava d'anta fodder (Dimorphandra gardneriana Tulasne)

The contamination of bodies of water by potentially hazardous elements has in recent decades become an environmental problem that poses serious risks to humans, fauna, flora and microbiota, compromising the quality of life of the present ecosystem. Therefore, effluents must be properly treated in a legally acceptable manner before their disposal in the environment. With this in mind, adsorption presents itself as an inexpensive efficient technique for the removal of potentially hazardous elements from effluents with excellent adsorption capacities when natural adsorbents are used. In this study, fava d'anta fodder was used in its crude and alkalinized form to remove Cu(II) and Pb(II) ions. Equilibrium studies were carried out using adsorption isotherms in batch systems with mono- and multi-elementary systems containing the two ions. The Langmuir and Freundlich models were applied to the isotherm studies, with the ions being better suited to the Langmuir model, with maximum adsorption capacities of 24.45 mg g^-1 and 68.49 mg g^-1 (crude form) and 11.12 mg g^-1 and 35.34 mg g^-1 (alkalinized form) in the mono-elementary system for Cu(II) and Pb(II) ions, respectively.

Fractionation of Heavy Metals in Multi-Contaminated Soil Treated with Biochar Using the Sequential Extraction Procedure

Heavy metals (HMs) toxicity represents a global problem depending on the soil environment’s geochemical forms. Biochar addition safely reduces HMs mobile forms, thus, reducing their toxicity to plants. While several studies have shown that biochar could significantly stabilize HMs in contaminated soils, the study of the relationship of soil properties to potential mechanisms still needs further clarification; hence the importance of assessing a naturally contaminated soil amended, in this case with Paulownia biochar (PB) and Bamboo biochar (BB) to fractionate Pb, Cd, Zn, and Cu using short sequential fractionation plans. The relationship of soil pH and organic matter and its effect on the redistribution of these metals were estimated. The results indicated that the acid-soluble metals decreased while the fraction bound to organic matter increased compared to untreated pots. The increase in the organic matter metal-bound was mostly at the expense of the decrease in the acid extractable and Fe/Mn bound ones. The highest application of PB increased the organically bound fraction of Pb, Cd, Zn, and Cu (62, 61, 34, and 61%, respectively), while the BB increased them (61, 49, 42, and 22%, respectively) over the control. Meanwhile, Fe/Mn oxides bound represents the large portion associated with zinc and copper. Concerning soil organic matter (SOM) and soil pH, as potential tools to reduce the risk of the target metals, a significant positive correlation was observed with acid-soluble extractable metal, while a negative correlation was obtained with organic matter-bound metal. The principal component analysis (PCA) shows that the total variance represents 89.7% for the TCPL-extractable and HMs forms and their relation to pH and SOM, which confirms the positive effect of the pH and SOM under PB and BB treatments on reducing the risk of the studied metals. The mobility and bioavailability of these metals and their geochemical forms widely varied according to pH, soil organic matter, biochar types, and application rates. As an environmentally friendly and economical material, biochar emphasizes its importance as a tool that makes the soil more suitable for safe cultivation in the short term and its long-term sustainability. This study proves that it reduces the mobility of HMs, their environmental risks and contributes to food safety. It also confirms that performing more controlled experiments, such as a pot, is a disciplined and effective way to assess the suitability of different types of biochar as soil modifications to restore HMs contaminated soil via controlling the mobilization of these minerals.

Iron Oxide Nanoparticles: Biosynthesis, Magnetic Behavior, Cytotoxic Effect

Iron oxide nanoparticles have attracted much attention because of their superparamagnetic properties and their potential applications in many fields such as magnetic storage devices, catalysis, sensors, superparamagnetic relaxometry (SPMR), and high-sensitivity biomolecule magnetic resonance imaging (MRI) for medical diagnosis and therapeutics. In this study, iron oxide nanoparticles (Fe2 O3 NPs) have been synthesized using a taranjabin (camelthorn or persian manna) aqueous solution. The synthesized Fe2 O3 NPs were identified through powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), field energy scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDX), vibrating-sample magnetometer (VSM) and Raman technics. The results show that the nanoparticles have a hexagonal structure with 20 to 60 nm in size. The cytotoxic effect of the synthesized nanoparticles has been tested upon application against lung cancer cell (A549) lines. It was found that there is no cytotoxic activity at lower concentrations of 200 μg/mL. The ability of the synthesized nanoparticles for lead removal in wastewaters was tested. Results show that highest concentration of adsorbent (50 mg/L) has maximum removal efficiency (96.73 %). So, synthesized Fe2 O3 NPs can be a good candidate to use as heavy metals cleaner from contaminated waters.

Facile and Fast Transformation of Nonluminescent to Highly Luminescent Metal-Organic Frameworks: Acetone Sensing for Diabetes Diagnosis and Lead Capture from Polluted Water

Metal-organic frameworks (MOFs) stand as one of the most promising materials for the development of advanced technologies owing to their unique combination of properties. The conventional synthesis of MOFs involves a direct reaction of the organic linkers and metal salts; however, their postsynthetic modification is a sophisticated route to produce new materials or to confer novel properties that cannot be attained through the traditional methods. This work describes the postsynthetic MOF-to-MOF transformation of a nonluminescent MOF (Zn-based Oxford University-1 material [Zn-BDC, where BDC = 1,4-benzene dicarboxylate] (OX-1)) into a highly luminescent framework (Ag-based Oxford University-2 material [Ag-BDC] (OX-2)) by a simple immersion of the former in a silver salt solution. The conversion mechanism exploits the uncoordinated oxygen atoms of terephthalate linkers found in OX-1, instead of the unsaturated metal sites commonly employed, making the reaction much faster. The materials derived from the OX-1 to OX-2 transformation are highly luminescent and exhibit a selective response to acetone, turning them into a promising candidate for manufacturing fluorometric sensors for the diagnosis and monitoring of diabetes mellitus. Our methodology can be extended to other metals such as lead (Pb). The fabrication of a polymer mixed-matrix membrane containing OX-1 is used as a proof-of-concept for capturing Pb ions (as pollutants) from water. This research instigates the exploration of alternative methodologies to confer MOFs with special aptitudes for photochemical sensing or for environmental applications such as water purification.

Environment-Induced Reversible Modulation of Optical and Electronic Properties of Lead Halide Perovskites and Possible Applications to Sensor Development: A Review

Lead halide perovskites are currently widely investigated as active materials in photonic and optoelectronic devices. While the lack of long term stability actually limits their application to commercial devices, several experiments demonstrated that beyond the irreversible variation of the material properties due to degradation, several possibilities exist to reversibly modulate the perovskite characteristics by acting on the environmental conditions. These results clear the way to possible applications of lead halide perovskites to resistive and optical sensors. In this review we will describe the current state of the art of the comprehension of the environmental effects on the optical and electronic properties of lead halide perovskites, and of the exploitation of these results for the development of perovskite-based sensors.

Study on novel modified large mesoporous silica FDU-12/polymer matrix nanocomposites for adsorption of Pb(II)

In this study, porous methacrylate-modified FDU-12/poly(methyl methacrylate) and amine-modified FDU-12/Nylon 6 nanocomposites were synthesized via a facile solution casting protocol. The physicochemical properties of the prepared materials were studied using various characterization techniques including Fourier transform-infrared spectroscopy, field emission-scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption/desorption. After characterization of the materials, the prepared nanocomposites were applied as novel adsorbents for the removal of Pb(II) from aqueous media. In this regard, the effect of various parameters including solution pH, adsorbent amount, contact time, and initial concentration of Pb(II) on the adsorption process was investigated. To study the mechanism of adsorption, kinetic studies were conducted. The kinetic models of pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion were employed. The results revealed that the adsorption of Pb(II) onto methacrylate-modified FDU-12/poly(methyl methacrylate) and amine-modified FDU-12/Nylon 6 adsorbents followed the pseudo-second-order kinetic model. Also, different isotherms including Langmuir, Freundlich, and Dubinin-Radushkevich were applied to evaluate the equilibrium adsorption data. Langmuir isotherm provided the best fit with the equilibrium data of both adsorbents with maximum adsorption capacities of 99.0 and 94.3 mg g-1 for methacrylate-modified FDU-12/poly(methyl methacrylate) and amine-modified FDU-12/Nylon 6, respectively, for the removal of Pb(II).

Sorption mechanisms of lead on soil-derived black carbon formed under varying cultivation systems

The knowledge about lead (Pb) sorption on soil-derived black carbons (SBCs) under different cultivation intensities of soils is limited. In this study, chemical and spectroscopic methods were applied to investigate the Pb sorption mechanisms on SBCs in soils from a forest land, a rubber plantation area, and a vegetable farm with none, less and highly intensive cultivation, respectively, that are located in the Hainan Island of China. Results showed that the specific surface area and cation exchange capacity of the SBCs from the less and highly intensive cultivation soils were 4.5- and 2.7-fold, and 1.3- and 1.8-fold higher compared to that of SBC from the no-cultivation soil, which subsequently enhanced the Pb sorption capacities of SBCs in iron exchange fraction. Ion exchange and hydrogen bonded Pb fractions together accounted for about 80% of total Pb sorbed on all SBCs at an externally added 1000 mg L^-1 Pb solution concentration. The OC-O groups also played key roles in Pb sorption by forming complexes of OC-O-Pb-O and/or OC-O-Pb. Overall, SBCs in soils under all studied cultivation intensities showed high potential to sorb Pb (with the maximum absorbed Pb amount of 46.0-91.3 mg g^-1), and increased Pb sorption capacities of the studied soils by 18.7-21.1 mg kg^-1 in the stable fraction (complexation). Therefore, SBC might be a potential environment-friendly material to enhance the Pb immobilization capacity of soil.

Process optimization and modeling of Pb(II) ions adsorption on chitosan-conjugated magnetite nano-biocomposite using response surface methodology

This study aimed to investigate the performance of a magnetic nano-biocomposite, chitosan conjugated magnetite nanoparticle (CH-MNP), for the removal of lead ions. The magnetite nanoparticles were synthesized through a controlled co-precipitation technique and were stabilized with citric acid. Subsequently, they were covalently bonded to chitosan via carbodiimide chemistry using EDAC/NHS activation. One of the notable advantages of this nano-biocomposite is its chemical conjugation, which does not have the weakness of the ultimate chitosan detachment of a physical bond and makes it an encouraging candidate for magnetic separation with no secondary waste production. The CH-MNPs had a diameter of ∼10 nm, with a saturation magnetization of 76.01 emu/g ensuring a superparamagnetic property. The response surface methodology (RSM) with a central composite design (CCD) framework was used for optimizing the adsorption process. The optimum conditions to achieve 92.15% of Pb(II) removal were found to be at a pH of 6.1 with the nano-adsorbent concentration of 1.04 g/L and a contact time of 59.92 min. Our adsorption isotherm data were fitted well with the Langmuir adsorption isotherm model, and the equilibrium data followed the pseudo-second-order kinetics and intraparticle diffusion kinetic model. The maximum Langmuir Pb(II) adsorption capacity was calculated to be 192.308 mg/g. These results suggest that the proposed synthetic nano-biocomposite is quite an ideal nano-adsorbent for Pb(II) removal in wastewater treatment technology.

Lead removal from water by a newly isolated Geotrichum candidum LG-8 from Tibet kefir milk and its mechanism

In this study, a yeast-like fungal strain (LG-8), newly isolated from spontaneous Tibet kefir in China, was identified as Geotrichum candidum on the basis of its morphological characteristics and ITS5.8S gene sequence. Interestingly, the strain was able to remove more than 99% of Pb²⁺ ions in water at low concentrations and a maximum of 325.68 mg lead/g of dry biomass. The results of selective passivation experiments suggested that phosphate, amide and carboxyl groups on the cell wall contributed to lead removal. Scanning electron microscopy (SEM) photomicrographs revealed that large amounts of micro/nanoparticles formed on the cell wall, and energy dispersive X-ray spectroscopy (EDX) results further indicated the presence of lead along with phosphorus and chlorine in the particles. Furthermore, the results of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses revealed that the particles were composed of pyromorphite [Pb₅(PO4)₃Cl], a highly insoluble lead mineral. Importantly, this is the first time that the biomineralization of lead into pyromorphite has been observed as the major mechanism for lead removal by G. candidum LG-8, providing a new strategy to scavenge heavy metals from aquatic environment in an eco-friendly manner.

Deep Eutectic Solvent-Based Microextraction of Lead(II) Traces from Water and Aqueous Extracts before FAAS Measurements

Microextraction procedures for the separation of Pb(II) from water and food samples extracts were developed. A deep eutectic solvent composed of α-benzoin oxime and iron(III) chloride dissolved in phenol was applied as a phase separator support. In addition, this deep eutectic mixture worked as an efficient extractor of Pb(II). The developed microextraction process showed a high ability to tolerate the common coexisting ions in the real samples. The optimum conditions for quantitative recoveries of Pb(II) from aqueous extracts were at pH 2.0, conducted by adding 150 µL from the deep eutectic solvent. The quantitative recoveries were obtained with various initial sample volumes up to 30 mL. Limits of detection and limits of quantification of 0.008 and 0.025 µg L^-1 were achieved with a relative standard deviation (RSD%) of 2.9, which indicates the accuracy and sensitivity of the developed procedure. Recoveries from the reference materials, including TMDA 64.2, TMDA 53.3, and NCSDC-73349, were 100%, 97%, and 102%, respectively. Real samples, such as tap, lake, and river water, as well as food samples, including salted peanuts, chickpeas, roasted yellow corn, pistachios, and almonds, were successfully applied for Pb(II) analysis by atomic absorption spectroscopy (AAS) after applying the developed deep eutectic solvent-based microextraction procedures.

Surface characterization of maize-straw-derived biochar and their sorption mechanism for Pb2+ and methylene blue

Biochar derived from straw is a potential low-cost adsorbent for metal ions and organic pollutants, but its practical application is still limited by the adsorption capacity. In this study, the correlation between the biochar’s properties and pyrolysis temperature was explored. The adsorption mechanism was studied by monitoring the changes of biochar properties before and after adsorption using BET, SEM, XPS and FT-IR spectroscopy. The adsorption mechanism was revealed following the adsorption kinetics and the changes in biochar’s properties before and after adsorption. The methylene blue (MB) and Pb²⁺ adsorption removal efficiency reached 95% at the initial concentration of 125 and 500 mg/L, respectively. Physisorption, chemisorption, and pore filling mechanisms determined the adsorption process of MB and Pb²⁺ on biochar. The Pb²⁺ adsorption process was highly affected by chemical co-precipitation at higher pyrolysis temperatures. The appearance of tar particles increased the adsorption rate of Pb²⁺. The biochar obtained at the pyrolysis temperature at 500, 800 and 900°C proved to be applicable for Pb²⁺ removal. Chemisorption and porosity dominated the MB adsorption, and biochars produced at pyrolysis temperatures of 200, 800 and 900°C are potential materials for MB removal. This study provides optimal pyrolysis conditions for transforming maize straw into valuable, low-cost materials for the removal of different pollutants.

Genetic Engineering-Facilitated Coassembly of Synthetic Bacterial Cells and Magnetic Nanoparticles for Efficient Heavy Metal Removal

Heavy-metal pollution is becoming a worldwide problem severely threatening our health and ecosystem. In this study, we constructed a genetic-engineering-driven coassembly of synthetic bacterial cells and magnetic nanoparticles (MNPs) for capturing heavy metals. The Escherichia coli cells were genetically engineered by introducing a de novo synthetic heavy-metal-capturing gene (encoding a protein SynHMB containing a six-histidine tag, two cystine-rich peptides, and a metallothionein sequence) and a synthetic type VI secretory system (T6SS) cluster of Pseudomonas putida, endowing the synthetic cells (SynEc2) with high ability of displaying the heavy-metal-capturing SynHMB on cell surface. MNPs were synthesized by a coprecipitation method and further modified by polyethylenimine (PEI) and diethylenetriaminepentaacetic acid (DTPA). Owing to the surface exposure of six-histidine tag on the synthetic bacteria and carboxyl groups on the modified MNPs (MNP@SiO₂-PEI-DTPA), the synthetic bacterial cells and MNPs coassembled to form biotic/abiotic complex exhibiting a self-developing characteristic. In the culture medium containing both Cd²⁺ and Pb²⁺, the coassemblies captured these heavy metals with high removal efficiency (>90% even at 50 mg/L of Cd²⁺ and 50 mg/L of Pb²⁺) and were conveniently recycled by artificial magnetic fields. Moreover, the coassemblies realized coremoval of organic carbon pollutants with the removal efficiency of >80%. This study builds a novel biotic/abiotic coassembling platform facilitated by genetic engineering and sheds light on development of artificial magnetic biological systems for efficient treatment of environmental pollution.

Activation of porous magnetized biochar by artificial humic acid for effective removal of lead ions

In this paper, we have successfully prepared porous magnetic biochar with excellent surface area and recovery rate using corn stalks (CS) and waste iron (WI) as precursors. Notably, in order to prevent the incorporated iron oxides from blocking the carbon pores, then resulting in a decrease in specific surface area and reducing the removal efficiency of the material, the optimum range of iron ions can be determined to be 0.04-0.06 mol/L according to the effect of the amount of iron on the magnetic biochar recovery rate and Pb²⁺ removal capacity. Furthermore, as-synthesized artificial humic acid (A-HA) obtained from waste biomass by hydrothermal humification (HTH) technology has abundant functional groups, which can complex with heavy metals and metal oxides. Therefore, A-HA is introduced as an activator to produce novel porous magnetic biochar materials (AHA/Fe₃O₄-γFe₂O₃@PBC) with abundant functional groups (i.e., phenolic-OH, -COOH, etc.), providing high dispersibility and stability, further leading to excellent removal performance (Langmuir removal capacity up to 99.82 mg/g) and recyclable performance (removal capacity after 5 removal cycles is 79.04 mg/g). Multiple removal mechanisms have been revealed, including reduction, complexation, and precipitation.

Mechanochemical immobilization of lead contaminated soil by ball milling with the additive of Ca(H2PO4)2

Lead (Pb) pollution in the soil is becoming more and more serious, and lead poisoning incidents also constantly occur. Therefore, the remediation of lead pollution in the soil has attracted widespread attention. In this study, heavy metal lead in soil was remediated by mechanochemical methods. The effects of different ball milling conditions on the toxic leaching concentration and morphological distribution (BCR sequential extraction procedure) of lead in contaminated soil were analyzed, including the addition of calcium dihydrogen phosphate (Ca(H₂PO₄)₂), ball milling time, and ball milling speed. The reaction mechanism was analyzed by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and a laser particle size analyzer. The results show that the optimal conditions for mechanochemical immobilization were 10% additive (Ca(H₂PO₄)₂), milling speed of 550 rpm, and ball milling time for 2 h. Under this condition, the toxic leaching concentration of lead from contaminated soil was 4.36 mg L^-1, and in the BCR sequential extraction procedure, Pb was mainly present in the residual fraction (54.96%). The mechanism of mechanochemical solidification of heavy metal lead in soil is that, during the ball milling process, the lead precipitates with Ca(H₂PO₄)₂ to produce dense agglomerates (Pb₃(PO₄)₂ and Pb_xCa_10-x(PO₄)₆(OH)₂), which fixes the lead in the soil and hampers its leaching.

Multi-component adsorption of Pb(II), Cd(II) and Ni(II) onto microwave-functionalized cellulose: Kinetics, isotherms, thermodynamics, mechanisms and application for electroplating wastewater purification

Herein, microwave-functionalized cellulose derived from rice husk was cost-effectively prepared and employed for Pb(II), Cd(II) and Ni(II) elimination in mono- and multi-component systems. Benefiting from microwave irradiation, the functionalized process was achieved in 6.5 min and the resultant RH_MW-X possessed remarkably high adsorption capacities of 295.20 mg/g for Pb(II), 151.51 mg/g for Cd(II) and 72.80 mg/g for Ni(II) within the equilibrium time of 30 min. Noticeably, the metal ions adsorption rate and capacity in binary and ternary systems were lower than that of unary systems. The coexistence of Cd(II) and Ni(II) significantly slowed down the Pb(II) adsorption in binary and ternary systems, while Pb(II) exhibited the most obvious influence on the metal ions uptake in the multi-component systems. FT-IR and XPS results revealed that both ion exchange and chelation were functioned in the metal ions uptake, while physical interaction was also involved in the adsorption process. Moreover, the RH_MW-X possessed favorable recyclability with slight adsorption efficiency decline during five cycles in different systems. Particularly, the RH_MW-X could effectively purify actual industrial wastewater containing Pb(II), Cd(II) and Ni(II) for meeting regulatory requirements. This work facilitates the omnidirectional improvement of adsorbents for the de-pollution of practical heavy metals wastewater.

Micro-nano-engineered nitrogenous bone biochar developed with a ball-milling technique for high-efficiency removal of aquatic Cd(II), Cu(II) and Pb(II)

A cost-effective and eco-friendly engineering method to improve biochar's physicochemical and sorption performance is critical in various environmental applications. In this study, micro-nano-engineered nitrogenous biochars derived from cow bone meal pyrolyzed at different temperatures and were engineered with the assistance of a ball-milling technique. The ball-milled bone biochars were natural composites combined with plant biochars and hydroxyapatite components on the micro-nanoscale. Both the micropore area and the external specific surface area of the bone biochars were significantly improved after ball-milling. The sorption capacities for heavy metal ions were heavy metal ions were MBC-600 > MBC-450 > BC-600 > MBC-300 > BC-450 > BC-300, consistent with the variation tendency in the specific surface areas of the bone biochars. The adsorption capacities of MBC-600 for Cd(II), Cu(II) and Pb(II) were 165.77, 287.58 and 558.88 mg/g, respectively (T 298K, pH 5.0), representing increases of 93.91.%, 75.56% and 64.61% compared with the un-milled preparation. Surface complexation, cation exchange, chemical precipitation, electrostatic interaction and cation-π bonding were responsible for the removal of heavy metal ions by bone biochar materials. Taken together, the results show that micro-nano-engineered nitrogenous bone biochar prepared using ball-milling technology is a promising material for the remediation of heavy metals-bearing aquatic environments.

Potential of pistachio shell biochar and dicalcium phosphate combination to reduce Pb speciation in spinach, improved soil enzymatic activities, plant nutritional quality, and antioxidant defense system

Lead-contaminated soils are becoming an ecological risk to the environment because of producing low-quality food which is directly causing critical health issues in humans and animals. We hypothesized that incorporation of dicalcium phosphate (DCP), eggshell powder (ESP) and biochar (BH) at diverse rates into a Pb-affected soil can proficiently immobilize Pb and decline its bioavailability to spinach (Spinacia oleracea L.). A soil was artificially spiked with Pb concentration (at 600 mg kg^-1) and further amended with DCP, ESP, and BH (as sole treatments at 2% and in concoctions at 1% each) for immobilization of Pb in the soil. The interlinked effects of applied treatments on Pb concentrations in shoots and roots, biomass, antioxidants, biochemistry, and nutrition of spinach were also investigated. Results depicted that the highest reduction in DTPA-extractable Pb and the concentrations of Pb in shoots and roots was achieved in DCP1%+BH1% treatment that was up to 58%, 66%, and 53%, respectively over control. Likewise, the DCP1%+BH1% treatment also showed the maximum shoot and root dry weight (DW), chlorophyll-a (Chl-a) and chlorophyll-b (Chl-b) contents and relative water content (RWC) in spinach up to 92%, 121%, 60%, 65%, and 30%, respectively, compared to control. Likewise, DCP1%+BH1% treatment noticeably improved antioxidant enzymes, biochemistry, and nutrition in the leaves. Moreover, the DCP1%+BH1% treatment depicted mostly enhanced activities of dehydrogenase, catalase, acid phosphatase, alkaline phosphatase, phosphomonoesterase, urease, protease and B-glucosidase in the post-harvested soil up to 118%, 345%, 55%, 92%, 288%, 107%, 53% and 252%, respectively over control.

Development and characterization of magnetic eggshell membranes for lead removal from wastewater

An increasing concern for natural resources preservation and environmental safety is the removal of heavy metals from contaminated water. It is essential to develop simple procedures that use ecofriendly materials with high removal capacities. In this context, we have synthesized a new hybrid material in which eggshell membranes (ESMs) act as nucleation sites for magnetite nanoparticles (MNPs) precipitation in the presence of an external magnetic field. As a result, ESM was transformed into a magnetic biomaterial (MESM) in order to combine the Pb adsorption abilities of both MNPs and ESM and to facilitate collection of the bioadsorbant using an external magnetic field. This green co-precipitation method produced long strands of bead-like 50 nm superparamagnetic MNPs decorating the ESM fibers. When MESM were incubated in Pb(NO₃)₂ solutions, the hybrid material displayed a 2.5-fold increase in binding constant with respect to that of ESM alone, and a 10-fold increased capacity to remove Pb ions from aqueous solution. The manufactured MESMs present a maximum loading capacity of 0.066 ± 0.009 mg Pb/mg MNPs at 25 °C, which is increased up to 0.15 ± 0.05 mg Pb/mg MNPs at 45 °C. Moreover, the MESM system is very stable, since incubation in 1% HCl solution resulted in rapid Pb desorption, while MNP release from the MESM during the same period was negligible. Altogether, these results suggest that MESM could be utilized as an efficient nanoremediation agent for separation/removal of heavy metal ions or other charged pollutants from contaminated waters, with facile recovery for recycling.

Effects of excessive impregnation, magnesium content, and pyrolysis temperature on MgO-coated watermelon rind biochar and its lead removal capacity

MgO-coated watermelon rind biochar (MWRB) is a potentially highly-effective waste-derived material in environmental applications. This research aims to provide valuable insights into the optimization of the production of MWRB for superior environmental performance. It was found that the Mg content of the MWRB could be easily controlled by adjusting the Mg/feedstock mass ratio during excessive impregnation. The BET surface area was found to first increase and then decrease as the Mg content of the MWRB (produced at 600 °C) increased from 1.52% to 10.1%, with an optimal surface area of 293 m²/g observed at 2.51%. Similarly, an optimum pyrolysis temperature of 600 °C was observed in the range of 400-800 °C for a maximum surface area of the MWRB at a fixed Mg/feedstock ratio of 0.48% (resulting in MWRBs with Mg contents of 1.89-2.51%). The Pb removal capacity of the MWRB (produced at 600 °C) increased with increasing Mg content, with a greatest Pb removal capacity of 558 mg/g found for the MWRB with the highest Mg content (10.1%), an improvement of 208% over the 181 mg/g Pb removal capacity of unmodified WRB produced at 600 °C. The Pb removal capacity of the MWRB (produced with 1.89-2.51% Mg) was also discovered to increase from 81.7 mg/g (at 400 °C) to 742 mg/g (at 700 °C), before dropping to 368 mg/g at 800 °C. These findings suggest that the MWRB can be more efficiently utilized in soil and water remediation by optimizing its synthesis conditions.

Monitoring the lead-and-copper rule with a water-gated field effect transistor

We use the natural zeolite clinoptilolite as the sensitive element in a plasticised PVC membrane. Separating a sample pool and a reference pool with such a membrane in water-gated SnO₂ thin-film transistor (SnO₂ WGTFT) leads to membrane potential, and thus transistor threshold shift in response to the common drinking water pollutants Pb²⁺ or Cu²⁺ in the sample pool. Threshold shift with ion concentration, c, follows a Langmuir-Freundlich (LF) characteristic. As the LF characteristic shows the steepest slope in the limit c → 0, this opens a window to limits-of-detection (LoDs) far below the 'action levels' of the 'lead-and-copper rule' for drinking water: Pb²⁺: LoD 0.9 nM vs 72 nM action level, Cu²⁺: LoD 14 nM vs 20.5 μM action level. LoDs are far lower than for membranes using organic macrocycles as their sensitive elements. Threshold shifts at the lead and copper action levels are more significant than shifts in response to variations in the concentration of non-toxic co-cations, and we discuss in detail how to moderate interference. The selective response to lead and copper qualifies clinoptilolite-sensitised WGTFTs as a low footprint sensor technology for monitoring the lead-and-copper rule, and to confirm the effectiveness of attempts to extract lead and copper from water.

Monitoring the Heavy Metal Lead Inside Living Drosophila with a FRET-Based Biosensor

The harmful impact of the heavy metal lead on human health has been known for years. However, materials that contain lead remain in the environment. Measuring the blood lead level (BLL) is the only way to officially evaluate the degree of exposure to lead. The so-called "safe value" of the BLL seems to unreliably represent the secure threshold for children. In general, lead's underlying toxicological mechanism remains unclear and needs to be elucidated. Therefore, we developed a novel genetically encoded fluorescence resonance energy transfer (FRET)-based lead biosensor, Met-lead, and applied it to transgenic Drosophila to perform further investigations. We combined Met-lead with the UAS-GAL4 system to the sensor protein specifically expressed within certain regions of fly brains. Using a suitable imaging platform, including a fast epifluorescent or confocal laser-scanning/two-photon microscope with high resolution, we recorded the changes in lead content inside fly brains ex vivo and in vivo and at different life stages. The blood-brain barrier was found to play an important role in the protection of neurons in the brain against damage due to the heavy metal lead, either through food or microinjection into the abdomen. Met-lead has the potential to be a powerful tool for the sensing of lead within living organisms by employing either a fast epi-FRET microscope or high-resolution brain imaging.

Selective recovery of lead and zinc through controlling cathodic potential in a bioelectrochemically-assisted electrodeposition system

Proper treatment of mining wastewaters is critically important to minimize contamination by heavy metals contained in those wastewaters. Herein, a bioelectrochemically-assisted electrodeposition (BES-EDP) system was developed and investigated for selective removal and recovery of Pb and Zn from a mimicked smelting wastewater. It was observed that those two metals were reduced at different cathodic potentials and electrodeposition time. At a cathodic potential of -0.75 V vs. Ag/AgCl, 98.5 ± 1.4 % of Pb was recovered after 10 h of reaction while there was little Zn deposition. Increasing the cathodic potential to -1.2 V could achieve 98.7 ± 0.7 % of Zn with the electrodeposition time of 6 h. The composition of the deposits confirmed the results from solution analysis and metal oxides were also formed during metal reduction. The diffusion impedance was much higher than the charge transfer resistance, suggesting that the diffusion process was a rate limiting step for electrodeposition. The diffusion process was verified by chronoamperometry with a good fit in Cottrell equation. The electrodeposition equilibrium constant k₀ was determined as 3.76 cm s^-1. Those results have demonstrated the feasibility of using bioelectricity to assist with selective metal recovery and warrant further investigation of technologies for sustainable management of mining wastewaters.

Influence of green waste compost on Pb-polluted soil remediation, soil quality improvement, and uptake by Pakchoi cabbage (Brassica campestris L. ssp)

Green waste compost (GWC) has been widely used as organic mulches, growing media, soil organic fertilizer, and amendment in Beijing, China. The aim of this study is to determine the remediation efficiency of GWC on the Pb concentration in soil and uptake by pakchoi cabbage and to assess the activities of dehydrogenase, urease, and catalase after applying GWC. Original soil samples were spiked with Pb (NO₃)₂ of 500 mg/kg, and greenhouse pot experiment was carried out. Three seedlings of pakchoi cabbage (Brassica campestris L. ssp) were planted in plastic pots with mixture of soil amended with three levels of GWC (2%, 5%, and 10%, w/w). Soil and plant samples were collected over 45-day growth, after which Pb concentration and enzyme activities were assessed by laboratory analysis. The available Pb in soil and total Pb in roots and leaves of pakchoi cabbage greatly decreased after adding GWC, associated with significant increases in organic matter, water soluble organic carbon, total nitrogen, and available K and P, whereas pH was not a main factor controlling Pb speciation in this study. Activities of dehydrogenase, urease, and catalase were promoted with addition of GWC because physical properties, high organic matter, and organic carbon content rose by 9-fold, 40%, and 37% at 10% application rate, respectively. In conclusion, GWC could be an alternative option for the remediation of Pb-contaminated soil because of soil quality improvement and Pb reduction in soils and plants, without introducing extra heavy metals compared with other organic amendments.

Simultaneous immobilization of the cadmium, lead and arsenic in paddy soils amended with titanium gypsum

In situ immobilization of heavy metals in contaminated soils using industrial by-products is an attractive remediation technique. In this work, titanium gypsum (TG) was applied at two levels (TG-L: 0.15% and TG-H: 0.30%) to simultaneously reduce the uptake of cadmium (Cd), lead (Pb) and arsenic (As) in rice grown in heavy metal contaminated paddy soils. The results showed that the addition of TG significantly decreased the pH and dissolved organic carbon (DOC) in the bulk soil. TG addition significantly improved the rice plants growth and reduced the bioavailability of Cd, Pb and As. Particularly, bioavailable Cd, Pb and As decreased by 35.2%, 38.1% and 38.0% in TG-H treatment during the tillering stage, respectively. Moreover, TG application significantly reduced the accumulation of Cd, Pb and As in brown rice. Real-time PCR analysis demonstrated that the relative abundance of sulfate-reducing bacteria increased with the TG application, but not for the iron-reducing bacteria. In addition, 16S rRNA sequencing analysis revealed that the relative abundances of heavy metal-resistant bacteria such as Bacillus, Sulfuritalea, Clostridium, Sulfuricella, Geobacter, Nocardioides and Sulfuricurvum at the genus level significantly increased with the TG addition. In conclusion, the present study implied that TG is a potential and effective amendment to immobilize metal(loid)s in soil and thereby reduce the exposure risk of metal(loid)s associated with rice consumption.

Enhanced passivation of lead with immobilized phosphate solubilizing bacteria beads loaded with biochar/ nanoscale zero valent iron composite

Phosphate solubilizing bacteria (PSBs) can effectively enhance the stability of lead via the formation of insoluble Pb-phosphate compounds. This research presents a bio-beads, which was implemented with the help of a self-designed porous spheres carrier, by immobilized PSBs strains Leclercia adecarboxylata (hereafter referred as L1-5). In addition, the passivation efficiency of lead via bio-beads under different conditions and its mechanism were also investigated in this study. The results indicated that phosphate solubilized by bio-beads could reach 30 mg/L in Ca₃(PO₄)₂ medium containing 1 mM Pb²⁺, and the highest removal rate of Pb²⁺ in beef peptone liquid medium could reach 93%, which is better than that of free bacteria. Furthermore, it was also concluded that the lead could be transformed into stable crystal texture, such as Pb₅(PO₄)₃Cl and Pb₅(PO₄)₃OH. Both hydrophobic and hydrophilic groups in the bio-beads could capture Pb²⁺, which indicated that electrostatic attraction and ion-exchange were also the mechanism of Pb²⁺ adsorption. All the experimental findings demonstrated that this bio-bead could be consider as an efficient way for the lead immobilization in contaminated soil in the future.

Removal of lead from acidic wastewater by bio-mineralized bacteria with pH self-regulation

Microorganisms with the function of bio-mineralization were isolated from a soil. They were identified as urease-producing bacteria and phosphate-solubilizing bacteria. These two kinds of bacteria belong to the eosinophilic bacteria, which regulated the pH of solution and removed Pb²⁺ the best at the initial solution pH of 4. The Pb²⁺ removal mechanism was further explored using various techniques including zeta potential measurement, three-dimensional fluorescence, FTIR, XRD, and TEM-EDS. The results showed that extracellular adsorption, intracellular accumulation and bio-mineralization occurred at the same time and converted to each other. The extracellular adsorption of urease-producing bacteria was through electrostatic adsorption and gradually decomposed urea to produce PbCO₃ minerals. The extracellular adsorption of phosphate-solubilizing bacteria was controlled by extracellular polymeric substances (EPS) and rapidly formation of Pb₃(PO₄)₂ stable minerals. In addition, the stabilities of Lead minerals of the two strains were compared. The results showed that the precipitates of phosphate-solubilizing bacteria were more stable. While phosphate-solubilizing bacteria have some advantages, both strains can play important roles in bio-mineralization of HMs in acidic wastewater.

Spent Ganoderma lucidum substrate derived biochar as a new bio-adsorbent for Pb2+/Cd2+ removal in water

The present study firstly reports spent Ganoderma lucidum substrate derived biochars (SLBCS) for the effective removal of Pb²⁺/Cd²⁺ from water. The effects of pyrolysis temperature on the SLBCS characteristics and Pb²⁺/Cd²⁺ adsorption mechanism was studied systematically. The surface physicochemical properties of SLBCS were significantly affected by the pyrolysis temperature. The increase in pyrolysis temperature from 250 to 650 °C resulted in a drastic increase in the biochar surface area and the well development of mesoporous structure, which could provide more effective adsorption sites for Pb²⁺ and Cd²⁺ onto SLBCS. According to the Langmuir model, the obtained maximum adsorption capacity of Pb²⁺ onto SL650 reached 262.76 mg g^-1, while that of Cd²⁺ reached 75.82 mg g^-1. The adsorption capacities of SL650 for Pb²⁺ and Cd²⁺ were even higher than that of other modified biochars. The high adsorption capacity of SL650 for Pb²⁺, attributed to the precipitation supported by high temperature, benefitted the formation of carbonate minerals. Two possible mechanisms involved in Cd²⁺ sorption: carbonate precipitation and coordination with π electrons. Desorption of SL650 showed high efficiency for Pb²⁺, but slightly low efficiency for Cd²⁺. These results indicate that SL650 can be applied for removing heavy metals, especially Pb²⁺, from polluted water.

Pb2+ biosorption from aqueous solutions by live and dead biosorbents of the hydrocarbon-degrading strain Rhodococcus sp. HX-2

In this study, the Pb²⁺ biosorption potential of live and dead biosorbents of the hydrocarbon-degrading strain Rhodococcus sp. HX-2 was analyzed. Optimal biosorption conditions were determined via single factor optimization, which were as follows: temperature, 25°C; pH, 5.0, and biosorbent dose, 0.75 g L⁻¹. A response surface software (Design Expert 10.0) was used to analyze optimal biosorption conditions. The biosorption data for live and dead biosorbents were suitable for the Freundlich model at a Pb²⁺ concentration of 200 mg L⁻¹. At this same concentration, the maximum biosorption capacity was 88.74 mg g⁻¹ (0.428 mmol g⁻¹) for live biosorbents and 125.5 mg g⁻¹ (0.606 mmol g⁻¹) for dead biosorbents. Moreover, in comparison with the pseudo-first-order model, the pseudo-second-order model seemed better to depict the biosorption process. Dead biosorbents seemed to have lower binding strength than live biosorbents, showing a higher desorption capacity at pH 1.0. The order of influence of competitive metal ions on Pb²⁺ adsorption was Cu²⁺ > Cd²⁺ > Ni⁺. Fourier-transform infrared spectroscopy analyses revealed that several functional groups were involved in the biosorption process of dead biosorbents. Scanning electron microscopy showed that Pb²⁺ attached to the surface of dead biosorbents more readily than on the surface of live biosorbents, whereas transmission electron microscopy confirmed the transfer of biosorbed Pb²⁺ into the cells in the case of both live and dead biosorbents. It can thus be concluded that dead biosorbents are better than live biosorbents for Pb²⁺ biosorption, and they can accordingly be used for wastewater treatment.

Removal of lead, zinc and cadmium from contaminated soils with two plant extracts: Mechanism and potential risks

Screening appropriate washing agents to remediate soils contaminated with heavy metals is crucial for decreasing metal hazards posing to environment and human health. In this study, two plant washing agents-water-extracted from Fagopyrum esculentum and Fordiophyton faberi, were applied to remove soil Pb, Zn, and Cd by washing. Results indicated that metal removals augmented with increase of washing solution concentrations, decreased with increasing pH values of the solution and followed the pseudo-second-order model depending on contact duration. At concentration of 50 g/L, pH 3 and contact duration of 120 min, F. esculentum had higher removals of Pb (5.98-6.83%), Zn (21.82-27.94%), and Cd (39.90-40.74%) than those of F. faberi. And metal ions could be removed by binding with carboxyl, hydroxyl, amide, amine and aromatic groups in washing solutions. The potential risks of residual metals declined by 51.35-52.12% for mine soil and 48.51-49.96% for farmland soil with exchangeable and carbonate-bound fractions obviously extracted after a single washing (P < 0.05). And soil organic carbon and nutrients increased to some extent except for total phosphorus and available potassium. Moreover, soil phytotoxicity lowered except that some adverse effects on seed germination existed. Therefore, the water extract from F. esculentum is a promising washing agent for heavy metal removal.

A facile foaming-polymerization strategy to prepare 3D MnO2 modified biochar-based porous hydrogels for efficient removal of Cd(II) and Pb(II)

A novel three dimensional MnO₂ modified biochar-based porous hydrogel (MBCG) was fabricated to overcome the low sorption capacity and difficulty in solid-liquid separation of biochar (BC) for Cd(II) and Pb(II) removal. BC was initially modified by a rapid redox reaction between KMnO₄ and Mn(II) acetate, and then incorporated into a polyacrylamide gel network via a rapid and facile free-radical polymerization. A foaming method was deliberately introduced during the fabrication to establish interpenetrated porous structure inside the network. Various characterizations were employed to examine the morphology, porous structures, chemical compositions, and mechanical properties of the samples. Adsorption performance of MBCG on Cd(II) and Pb(II) (isotherms and kinetics) as well as its desorption and reusability were also investigated. The results indicated that MnO₂ modified biochars (MBC) were successfully introduced and homogeneously distributed in the porous bulk hydrogel, endowing MBCG with more uniform pore structure, excellent thermostability, remarkable mechanic strength, and superior adsorption performance. The maximum Langmuir adsorption capacity on Cd(II) and Pb(II) is 84.76 and 70.90 mg g^-1, respectively, which is comparable or even larger than that of MBC. More importantly, MBCG can be rapidly separated and easily regenerated with an excellent reusability, which could retain 92.1% and 80.5% of the initial adsorption capacities of Cd(II) and Pb(II) after five cycles. These new insights make MBCG an ideal candidate in practical applications in water treatment and soil remediation contaminated with various heavy metals.

Enhanced interlayer trapping of Pb(II) ions within kaolinite layers: intercalation, characterization, and sorption studies

Lead (Pb(II)) pollution in water poses a serious threat to human health in many parts of the world. In the past decades, research has been aimed at developing efficient and cost-effective methods to address the problem. In this study, dimethyl sulfoxide (DMSO) and potassium acetate (K-Ac) intercalated kaolinite complexes were synthesized and subsequently utilized for Pb(II) removal from water. The intercalation of kaolinite with DMSO was found to be useful for expanding the interlayer space of the clay mineral from 0.72 to 1.12 nm. Kaolinite intercalation with K-Ac (KDK) increased the interlayer space from 1.12 to 1.43 nm. The surface area of KDK was found to be more than threefold higher as compared to natural kaolinite (NK). Batch experimental results revealed that the maximum Pb(II) uptake capacity of KDK was 46.45 mg g^-1 which was higher than the capacity of NK (15.52 mg g^-1). Reusability studies showed that KDK could be reused for 5 cycles without substantially losing its adsorption capacity. Furthermore, fixed-bed column tests confirmed the suitability of KDK in continuous mode for Pb(II) removal. Successful application of intercalated kaolinite for Pb(II) adsorption in batch and column modes suggests its application in water treatment (especially removal of divalent metals).

An environmental friendly enrichment method for microextraction of cadmium and lead in groundwater samples: Impact on biological sample of children

A novel ionic liquid-based vortex assisted dispersive liquid-liquid micro extraction procedure(IL-VADLLμE) was proposed for the enrichment of toxic metals, cadmium (Cd) and lead (Pb) in different types of water samples, domestic treated and groundwater (tube well and hand pump). Whereas, the concentration of both toxic metals was also determined in the scalp hair of children (age ranged 1-3 years), drinking contaminated groundwater termed as exposed group, whereas for comparative purposes scalp hair of age matched children consumed domestically treated water, named as non-exposed group. To preconcentrate the trace levels of Cd and Pb, a green chelating agent, l-cysteine (2-amino-3-sulfhydrylpropanoic acid) was used for complexation, an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM] [PF₆] utilized as extractant and hexafluorophosphate ion (PF₆^-) as anion pairing agent, which facilitate the enrichment of hydrophobic complexes of analytes into the acceptor phase. Various operative features for the IL-VADLLμE method like pH of standards/samples, volume of ionic liquid and sample solution, concentration of ligand, ion pair reagent and ionic liquid, vortex and electrical shaking time (for comparative purpose), were thoroughly optimized. The projected method was effectively applicable to assess the Cd and Pb in trace level in real water sample (surface and groundwater) and scalp hair samples of children belongs to exposed and non-exposed areas. The high contents of both toxic metals in scalp hair samples of children consuming groundwater indicate that the adverse impacts of both toxic metals especially Pb on the general health as well as neuron and skeletal problem, from child hood.

Adsorption of copper(II) and lead(II) from seawater using hydrothermal biochar derived from Enteromorpha

The objective of this research was to evaluate the capacity of Enteromorpha derived biochar to adsorb heavy metals from seawater. The biochar characteristics were determined, and isothermal and kinetic data were obtained using batch experiments. Copper [Cu(II)] and lead [Pb(II)] adsorption by the biochar was favored by high pH conditions, while elevated salinity had a relatively weak negative effect on adsorption. The Langmuir isotherm and adsorption kinetics pattern enabled interpretation of the equilibrium and kinetics of Cu(II) and Pb(II) removal by the biochar. The maximum removal rates of Cu(II) and Pb(II) by the biochar in 60 min were estimated to be 91% and 54%, respectively. A model describing the adsorption processes was developed to predict the efficiency of heavy metal removal by the biochar. The outcomes of the present study indicate that Enteromorpha derived biochar could be an effective and environmentally friendly adsorbent for removing heavy metals from marine environments.

Performance evaluation of A2O MBR system with graphene oxide (GO) blended polysulfone (PSf) composite membrane for treatment of high strength synthetic wastewater containing lead

High strength synthetic wastewater containing 5 mg L^-1 of lead was studied for treatment using an A2O MBR system. The system showed 99% removal of ammonia and COD, a maximum removal of 52% of total phosphorus and an average minimum removal of 72% of total nitrogen. A maximum lead removal of 98% was achieved for hydraulic retention time (HRT) of 144 h, which decreased to 85% when the influent COD concentration was decreased. Mass balance for lead revealed that much of its removal was through accumulation by the biomass present in the anaerobic and anoxic tanks. Comparative study on virgin PSf and GO blended PSf membrane showed that the GO blended membrane lasted 1.4 times longer than the other. SEM-EDS of membranes showed lead peaks on the fouled and un-fouled sections of the membranes indicating the association of lead with the foulant and the role of membrane in lead separation. Good separation efficiency was achieved irrespective of the membranes used.

One-pot synthesis of multi-functional and environmental friendly tannic acid polymer with Fe3+ and formaldehyde as double crosslinking agents for selective removal of cation pollutants

A novel multi-functional and environmental friendly tannic acid polymer (Fe³⁺-TA-HCHO) with Fe³⁺ and formaldehyde as double crosslinking agents together with cysteine as heteroatom source was prepared by a one-pot hydrothermal method. Characterization with transmission electron microscope (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FT-IR), and elemental analysis demonstrated that the Fe³⁺-TA-HCHO possessed uniform structure and particle size as well as plentiful functional groups. The resulted Fe³⁺-TA-HCHO material as a adsorbent to remove methylene blue, sunset yellow, Pb²⁺, Hg²⁺, and AsO₃^3- from water. The results suggested that Fe³⁺-TA-HCHO polymer (pHpzc is 2.33) showed different adsorption properties for anionic pollutants (sunset yellow and AsO₃^3-) and cationic pollutants (methylene blue, Pb²⁺, and Hg²⁺). The material exhibited remarkable selectivity for adsorption and separation of pollutants. The maximum adsorption capacities calculated from Langmuir model for methylene blue, Pb²⁺, and Hg²⁺ were 154.32, 819.67, and 699.30 mg g^-1, respectively. This is the first time that tannic acid polymer is synthesized by double crosslinking method, which not only developed a promising adsorbent for selective removal of cation pollutants, but also opened up a new avenue for synthesis and application of tannic acid polymer.

Assessment of By-Product from Botryosphaeria rhodina MAMB-05 as an Effective Biosorbent of Pb(II)

In this work, two types of biomass preparations (VMSM and M3) from the filamentous fungus Botryosphaeria rhodina MAMB-05, which were previously used in a process of production of β-glucan, were assessed as biosorbents of lead. The operating conditions, optimized through response surface methodology and experimental design, were shown to be pH 5.29 and a biosorbent dose of 0.23 g/L for the VMSM biomass type; and pH 5.06 and a dose of biosorbent of 0.60 g/L for the M3 biomass type, at a constant temperature of 27 °C. Fourier transform-infrared spectroscopy analyzed the presence of functional groups on the biomass surface. In addition to give an extra value to the by-product biomass, the VMSM-type from B. rhodina MAMB-05 showed an excellent lead biosorption capacity (q_m) with a value of 403.4 mg/g for the Langmuir model, comparing favorably with literature results, while the M3 subtype biomass showed a value of 96.05 mg/g.

Selection of the Optimal Spectral Resolution for the Cadmium-Lead Cross Contamination Diagnosing Based on the Hyperspectral Reflectance of Rice Canopy

This paper proposed an optimal spectral resolution for diagnosing cadmium-lead (Cd-Pb) cross contamination with different pollution levels based on the hyperspectral reflectance of rice canopy. Feature bands were sequentially selected by two-way analysis of variance (ANOVA2) and random forests from the high-dimensional hyperspectral data after preprocessing. Then Support Vector Machine (SVM) was applied to diagnose the pollution levels using different feature bands combination with different spectral resolutions and cross validation was conducted to evaluate the distinguishing accuracies. Finally, the optimal spectral resolution could be determined by comparing the diagnosing accuracies of the optimal feature bands combination in each spectral resolution. In the experiments, the hyperspectral reflectance data of rice canopy with ten different spectral resolutions was captured, covering 16 pretreatments of Cd and Pb pollution. The experimental results showed the optimal spectral resolution was 9 nm with the highest average accuracy of 0.71 and relatively standard deviation of 0.07 for diagnosing the categories and levels of Cd-Pb cross contamination. The useful exploration provided an evidence for optimal spectral resolution selection to reduce the cost of heavy metal pollution diagnose.

Assessment of Pb2+ removal capacity of lichen (Evernia prunastri): application of adsorption kinetic, isotherm models, and thermodynamics

Biological materials play a significant role in the treatment of heavy metal-contaminated soil and wastewater. In this study, the Pb²⁺ biosorption potential of lichen Evernia prunastri, extensively available at a forest in Bilecik-Turkey, was investigated at batch-scale level. The optimal conditions were determined and the adsorption isotherms, kinetics, and thermodynamic calculations were also done. In order to have detailed knowledge about metal biosorption, SEM, FTIR, and BET analyses were carried out before and after the biosorption process. The optimal pH was found pH 4 and the maximum metal uptake capacity was found as 0.067 mol kg^-1. The results of this study indicate that the lichen was effectively applied to the removal of Pb²⁺ process as an inexpensive biosorbent from industrial wastewater.

Pb2+ adsorption on TiO2 @HF-waste building bricks: Kinetics, thermodynamics, and mechanisms

Pb²⁺ pollution poses severe threats to human health and ecosystem. In this study, based on the waste building bricks (WBB), the TiO₂ @HF-WBB was prepared for Pb²⁺ adsorption removal from wastewater. The adsorption of Pb²⁺ on TiO₂ @HF-WBB followed the pseudo-second-order kinetics and the Freundlich isotherm model. The thermodynamic parameters indicated that the adsorption process was endothermic, spontaneous, and irreversible, and also included physical adsorption and chemical adsorption simultaneously. Ca²⁺ and Mg²⁺ had little effect on Pb²⁺ adsorption. The effluent of fixed-bed was below 3 μg/L within 1,000 BV. The desorption rate could reach 90% by simple operation. The possible mechanisms included the electrostatic interaction and the complexation. PRACTITIONER POINTS: Waste building bricks were utilized for Pb²⁺ removal from wastewater. The effluent of fixed-bed was below 3 μg/L within 1,000 BV. TiO₂ @HF-WBB has excellent adsorption property and desorption property. Possible mechanisms are electrostatic interaction and the complexation.

Investigation of a combined continuous flow system for the removal of Pb and Cd from heavily contaminated soil

In this study, a combined continuous flow system was designed to remove Pb and Cd from heavily contaminated mine tailing soils. 0.05 M Na₂EDTA was used as a chelating agent to remove Pb and Cd from polluted soil, taken from the vicinity of Kayseri ÇİNKUR, Turkey. The initial concentrations of Pb and Cd were 16381 ± 643 and 34347 ± 1310 mg kg^-1, respectively. The electrochemical treatment process was applied to the waste washing solution, which emerged after being extracted from soil column and contained Pb and Cd. Metal ions were transformed to the metallic form by applying the electrochemical treatment process to the washing solution, containing Pb²⁺ and Cd²⁺. At the end of the leaching experiment, which was done with a 50 g soil sample in the soil column system, Pb and Cd removal efficiencies from soil were 59.72% and 58.01%, respectively. Then, the soil column solution was subjected to electrolysis through a 48 h period at 10 V. The electrochemical removal efficiency of ions, which moved from column to solution, was 84.46% for Pb and 59.21% for Cd.

Lead sorption characteristics of various chicken bone part-derived chars

Recycling food waste for beneficial use is becoming increasingly important in resource-limited economy. In this study, waste chicken bones of different parts from restaurant industry were pyrolyzed at 600 °C and evaluated for char physicochemical properties and Pb sorption characteristics. Lead adsorption isotherms by different chicken bone chars were carried out with initial Pb concentration range of 1-1000 mg L^-1 at pH 5. The Pb adsorption data were better described by the Langmuir model (R² = 0.9289-0.9937; ARE = 22.7-29.3%) than the Freundlich model (R² = 0.8684-0.9544; ARE = 35.4-72.0%). Among the chars derived from different chicken bone parts, the tibia bone char exhibited the highest maximum Pb adsorption capacity of 263 mg g^-1 followed by the pelvis (222 mg g^-1), ribs (208 mg g^-1), clavicle (179 mg g^-1), vertebrae (159 mg g^-1), and humerus (135 mg g^-1). The Pb adsorption capacities were significantly and positively correlated with the surface area, phosphate release amount, and total phosphorus content of chicken bone chars (r ≥ 0.9711). On the other hand, approximately 75-88% of the adsorbed Pb on the chicken bone chars was desorbable with 0.1 M HCl, indicating their recyclability for reuse. Results demonstrated that chicken bone char could be used as an effective adsorbent for Pb removal in wastewater.