Removal of lead from contaminated water bodies using sea nodule as an adsorbent

Delamination of multilayer Ti3C2Tx MXene alters its adsorpiton and reduction of heavy metals in water

MXenes are considered as an emerging class of two-dimensional (2D) adsorbent for various environmental applications. In this work, two different morphologies of Ti₃C₂T_x MXene (multilayer (ML-Ti₃C₂T_x) and delaminated titanium carbide (DL-Ti₃C₂T_x)) were prepared through mild in situ HF etching and further delamination. The structural differences between the two were explored with a focus on their effects on the performance and mechanism of removing heavy metals from water. In comparison to ML-Ti₃C₂T_x, DL-Ti₃C₂T_x had more oxygen-containing functional groups, higher specific surface area (19.713 vs. 8.243 m²/g), larger pore volume (0.135 vs. 0.040 cm³/g), higher maximum Pb(II) adsorption capacity (77.0 vs. 56.68 mg/g), but lower maximum Cu(II) adsorption capacity (23.08 vs. 55.46 mg/g). Further investigation revealed that the removal of Pb(II) by the MXenes was mainly controlled through electrostatic attraction and surface complexation mechanisms, while Cu(II) was removed mainly through surface reduction by Ti-related groups. Because delamination of ML-Ti₃C₂T_x increased the surface area and surface functional groups, DL-Ti₃C₂T_x became a better sorbent for Pb(II) in water. During sonication, however, delamination inevitably led to partial oxidation of Ti₃C₂T_x nanosheets and thus weakened the reducing ability of DL-Ti₃C₂T_x for Cu(II) in water. Nevertheless, both ML- and DL-Ti₃C₂T_x not only exhibited excellent heavy metal adsorption capacity under different solution conditions, but also showed good reusability. Findings of this study indicate that Ti₃C₂T_x MXenes are promising adsorbents for treating heavy metal pollutants in water.

Removal of car battery heavy metals from wastewater by activated carbons: a brief review

Spent automobile batteries are one of the most significant secondary sources of harmful heavy metals for the environment. After being incorporated into the aquatic ecosystems, these metals disseminate to various plants, microorganisms, and the human body and cause multiple adverse effects. Activated carbons (ACs) have long been used as an effective adsorbent for different heavy metals in wastewater treatment processes. Although numerous research works have been published to date on this topic, they are scattered in the literature. In this review, we have assembled these works and provided an extensive overview of the application of ACs for treating spent car battery heavy metals (CBHMs) from aquatic systems. The preparation of ACs from different precursor materials, their application in the adsorption of CBHMs, the adsorption mechanism, kinetics, adsorption isotherms and various parameters that may affect the adsorption processes have been discussed in detail. A brief comparative analysis of the adsorption performances of ACs prepared from different precursor materials is also provided. Finally, recommendations for future research works are also offered.

Biochar derived from fruit by-products using pyrolysis process for the elimination of Pb(II) ion: An updated review

Water pollution is one of the most concerning global environmental problems in this century with the severity and complexity of the issue increases every day. One of the major contributors to water pollution is the discharge of harmful heavy metal wastes into the rivers and water bodies. Without proper treatment, the release of these harmful inorganic waste would endanger the environment by contaminating the food chains of living organisms, hence, leading to potential health risks to humans. The adsorption method has become one of the cost-effective alternative treatments to eliminate heavy metal ions. Since the type of adsorbent material is the most vital factor that determines the effectiveness of the adsorption, continuous efforts have been made in search of cheap adsorbents derived from a variety of waste materials. Fruit waste can be transformed into valuable products, such as biochar, as they are composed of many functional groups, including carboxylic groups and lignin, which is effective in metal binding. The main objective of this study was to review the potential of various types of fruit wastes as an alternative adsorbent for Pb(II) removal. Following a brief overview of the properties and effects of Pb(II), this study discussed the equilibrium isotherms and adsorption kinetic by various adsorption models. The possible adsorption mechanisms and regeneration study for Pb(II) removal were also elaborated in detail to provide a clear understanding of biochar produced using the pyrolysis technique. The future prospects of fruit waste as an adsorbent for the removal of Pb(II) was also highlighted.

A State-of-the-Art Review on Innovative Geopolymer Composites Designed for Water and Wastewater Treatment

There is nothing more fundamental than clean potable water for living beings next to air. On the other hand, wastewater management is cropping up as a challenging task day-by-day due to lots of new additions of novel pollutants as well as the development of infrastructures and regulations that could not maintain its pace with the burgeoning escalation of populace and urbanizations. Therefore, momentous approaches must be sought-after to reclaim fresh water from wastewaters in order to address this great societal challenge. One of the routes is to clean wastewater through treatment processes using diverse adsorbents. However, most of them are unsustainable and quite costly e.g. activated carbon adsorbents, etc. Quite recently, innovative, sustainable, durable, affordable, user and eco-benevolent Geopolymer composites have been brought into play to serve the purpose as a pretty novel subject matter since they can be manufactured by a simple process of Geopolymerization at low temperature, lower energy with mitigated carbon footprints and marvellously, exhibit outstanding properties of physical and chemical stability, ion-exchange, dielectric characteristics, etc., with a porous structure and of course lucrative too because of the incorporation of wastes with them, which is in harmony with the goal to transit from linear to circular economy, i.e., "one's waste is the treasure for another". For these reasons, nowadays, this ground-breaking inorganic class of amorphous alumina-silicate materials are drawing the attention of the world researchers for designing them as adsorbents for water and wastewater treatment where the chemical nature and structure of the materials have a great impact on their adsorption competence. The aim of the current most recent state-of-the-art and scientometric review is to comprehend and assess thoroughly the advancements in geo-synthesis, properties and applications of geopolymer composites designed for the elimination of hazardous contaminants viz., heavy metal ions, dyes, etc. The adsorption mechanisms and effects of various environmental conditions on adsorption efficiency are also taken into account for review of the importance of Geopolymers as most recent adsorbents to get rid of the death-defying and toxic pollutants from wastewater with a view to obtaining reclaimed potable and sparkling water for reuse offering to trim down the massive crisis of scarcity of water promoting sustainable water and wastewater treatment for greener environments. The appraisal is made on the performance estimation of Geopolymers for water and wastewater treatment along with the three-dimensional printed components are characterized for mechanical, physical and chemical attributes, permeability and Ammonium (NH4+) ion removal competence of Geopolymer composites as alternative adsorbents for sequestration of an assortment of contaminants during wastewater treatment.

Tight sorption of arsenic, cadmium, mercury, and lead by edible activated carbon and acid-processed montmorillonite clay

Heavy metal exposure in humans and animals commonly occurs through the consumption of metal-contaminated drinking water and food. Although many studies have focused on the remediation of metals by purification of water using sorbents, limited therapeutic sorbent strategies have been developed to minimize human and animal exposures to contaminated water and food. To address this need, a medical grade activated carbon (MAC) and an acid processed montmorillonite clay (APM) were characterized for their ability to bind heavy metals and mixtures. Results of screening and adsorption/desorption isotherms showed that binding plots for arsenic, cadmium, and mercury sorption on surfaces of MAC (and lead on APM) fit the Langmuir model. The highest binding percentage, capacity, and affinity were shown in a simulated stomach model, and the lowest percentage desorption (< 18%) was shown in a simulated intestine model. The safety and protective ability of MAC and APM were confirmed in a living organism (Hydra vulgaris) where 0.1% MAC significantly protected the hydra against As, Cd, Hg, and a mixture of metals by 30-70%. In other studies, APM showed significant reduction (75%) of Pd toxicity, compared with MAC and heat-collapsed APM, suggesting that the interlayer of APM was important for Pb sorption. This is the first report showing that edible sorbents can bind mixtures of heavy metals in a simulated gastrointestinal tract and prevent their toxicity in a living organism. Graphical abstract.

Excellent adsorptive performance of a new nanocomposite for removal of toxic Pb(II) from aqueous environment: Adsorption mechanism and modeling analysis

Herein, a novel nanocomposite (Fe₃O₄@TATS@ATA) was prepared and used for adsorptive removal of Pb(II) ions from aqueous environment. The magnetic nanocomposite (Fe₃O₄@TATS@ATA) was characterized using FTIR, TEM, SEM, EDX, element mapping analysis (EMA), TGA analysis, XRD patterns, VSM, BET analysis, XPS spectrum, and zeta potential. The FTIR study confirmed the modification of Fe₃O₄ nanoparticles with triaminetriethoxysilane and 2-aminoterephthalic acid while XPS analysis (with peaks at 283.6, 285.1, 286.3, 284.5.0, 288.4 eV) displayed the presence of CSi, CN, OCNH, CC/CC and OCO functional groups, respectively on Fe₃O₄@TATS@ATA. The BET surface area, average pore size, pore volume and magnetization saturation for Fe₃O₄@TATS@ATA were found to be 114 m²/g, 6.4 nm, 0.054 cm^-3/g, and 22 emu/g, respectively. The adsorption isotherm data showed that Pb(II) adsorption onto Fe₃O₄@TATS@ATA fitted to Langmuir and Dubinin-Raduskevich isotherm model due to better R² value which was greater than 0.9 and q_m of Pb(II) was 205.2 mg/g at pH 5.7 in 150 min. Adsorption kinetics data displayed that Pb(II) adsorption onto Fe₃O₄@TATS@ATA was fitted to the pseudo-second-order and Elovich kinetic models. Thermodynamic outcomes exhibited the exothermic and spontaneous nature of adsorption. Results showed that Fe₃O₄@TATS@ATA nanocomposite was promising material for efficient removal of toxic Pb(II) from aqueous environment.

Facile conversion of kaolinite into clay nanotubes (KNTs) of enhanced adsorption properties for toxic heavy metals (Zn2+, Cd2+, Pb2+, and Cr6+) from water

Kaolinite nanotubes (KNTs) were synthesized from kaolinite by ultrasonic scrolling and characterized using X-ray diffractometer, scanning and transmission electron microscopes; and FTIR-FT Raman spectrometer. The synthetic KNTs appear as multi-walled scrolls of 12 nm average pore diameter and 50-600 nm particle length; and exhibit surface area of 105 m²/g. KNTs were used as adsorbents for Zn²⁺, Cd²⁺, Pb²⁺, and Cr⁶⁺ with uptake capacities of 103 mg/g, 116 mg/g, 89 mg/g, and 91 mg/g, respectively. The equilibration time of Cd²⁺ and Pb²⁺ adsorption is 360 min and for Cr⁶⁺ and Zn²⁺ area 120 min and 240 min, respectively. KNTs adsorption systems can be described mainly by Lagergren-second order and Freundlich models (R²> 0.95) as kinetic and isotherm models. This reflected multilayer adsorption forms with chemical sharing or ion exchange processes. KNTs exhibits high reusability and used for five cycles in the removal of the studied metals (100 mg/L). The removal percentages declined by 20.5%, 15.12%, 22.8% and 23.16% with repeating the reused cycles from cycle 1 to cycle 5 for Zn²⁺, Cd²⁺, Pb²⁺, and Cr⁶⁺, respectively. KNTs were applied successfully in realistic purification of tap water, groundwater, and sewage water from the inspected metals.

Development of magnetic porous coordination polymer adsorbent for the removal and preconcentration of Pb(II) from environmental water samples

A novel porous coordination polymer adsorbent (BTCA-P-Cu-CP) based on a piperazine(P) as a ligand and 1,2,4,5-benzenetetracarboxylic acid (BTCA) as a linker was synthesized and magnetized to form magnetic porous coordination polymer (BTCA-P-Cu-MCP). Fourier transform infrared (FTIR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), field emission scanning electron microscope(FESEM), energy-dispersive X-ray spectroscopy(EDS), CHN, and Brunauer-Emmett-Teller(BET) analysis were used to characterize the synthesized adsorbent. BTCA-P-Cu-MCP was used for removal and preconcentration of Pb(II) ions from environmental water samples prior to flame atomic absorption spectrometry(FAAS) analysis. The maximum adsorption capacity of BTCA-P-Cu-MCP was 582 mg g^-1. Adsorption isotherm, kinetic, and thermodynamic parameters were investigated for Pb(II) ions adsorption. Magnetic solid phase extraction (MSPE) method was used for preconcentration of Pb(II) ions and the parameters influencing the preconcentration process have been examined. The linearity range of proposed method was 0.1-100 μg L^-1 with a preconcentration factor of 100. The limits of detection and limits of quantification for lead were 0.03 μg L^-1 and 0.11 μg L^-1, respectively. The intra-day (n = 7) and inter-day (n = 3) relative standard deviations (RSDs) were 1.54 and 3.43% respectively. The recoveries from 94.75 ± 4 to 100.93 ± 1.9% were obtained for rapid extraction of trace levels of Pb(II) ions in different water samples. The results showed that the BTCA-P-Cu-MCP was steady and effective adsorbent for the decontamination and preconcentration of lead ions from the aqueous environment.

Application of artificial neural network for prediction of Pb(II) adsorption characteristics

The adsorption of Pb(II) onto the surface of microwave-assisted activated carbon was studied through a two-layer feedforward neural network. The activated carbon was developed by microwave activation of Acacia auriculiformis scrap wood char. The prepared adsorbent was characterized by using Brunauer-Emmett-Teller (BET) surface area analyzer, scanning electron microscope (SEM), and X-ray difractometer. In the present study, the input variables for the proposed network were solution pH, contact time, initial adsorbate concentration, adsorbent dose and temperature, whereas the output variable was the percent Pb(II) removal. The network had been trained by using different algorithms and based on the lowest mean squared error (MSE) value and validation error, resilient backpropagation algorithm with 12 neurons in the hidden layer was selected for the present investigation. The tan sigmoid and purelin transfer function were used in the hidden and the output layers of the proposed network, respectively. The model predicted and experimental values of the percent Pb(II) removal were also compared and both the values were found to be in reasonable agreement with each other. The performance of the developed network was further improved by normalizing the experimental data set and it was found that after normalization, the MSE and validation error were reduced significantly. The sensitivity analysis was also performed to determine the most significant input parameter.

High performance SiO2-nanoparticles-immobilized-Penicillium funiculosum for bioaccumulation and solid phase extraction of lead

Novel biosorbent systems were designed, investigated and implemented for bioaccumulation of Pb(II) from aqueous solutions. These are based on the combination of SiO(2)-nanoparticles (N-Si) with Penicillium funiculosum fungus (Pen) for the formation of (N-Si-Pen) as well as heat inactivated Penicillium funiculosum (Pen). The SiO(2)-nanoparticles were also investigated as a solid sorbent phase. Surface characterization and immobilization were examined and confirmed by using FT-IR and SEM analysis. A batch equilibrium technique was used to follow-up the adsorption processes of lead under the effect of pH, contact time, sorbent dosage and initial metal concentration. The maximum capacity values were 1200.0 and 1266.7μmolg(-1) for (Pen) and (N-Si-Pen), respectively at pH 5. Sorption equilibria were established in ∼20min and their data were well described by Langmuir, Freundlich and Dubinin-Radushkevich models. The potential applications of these biosorbents for extraction of Pb(II) from real samples contaminated with lead, were successfully accomplished.

Characterization and lead adsorption properties of activated carbons prepared from cotton stalk by one-step H3PO4 activation

Activated carbons were prepared from cotton stalk by one-step H(3)PO(4) activation and used as adsorbent for the removal of lead(II). Taguchi experimental design method was used to optimize the preparation of the adsorbents. The results showed that the optimized conditions were: impregnation with a 50% (w/v) phosphoric acid solution with a mass ratio of 3:2 and activation temperature at 500 degrees C for 60 min with the rate of achieving the activation temperature equal to 10 degrees C min(-1). The cotton stalk activated carbon (CSAC) prepared at these conditions have 1.43 mmol g(-1) acidic surface groups and 1570 m(2) g(-1) BET surface area. Adsorption isotherms for lead(II) on the adsorbents were measured by conducting a series of batch adsorption experiments. The Langmuir maximum adsorption amount of lead(II) on CSAC was more than 119 mg g(-1), which was superior to the ordinary commercial activated carbon (CAC) on the market. Compared with the CAC, the CSAC had a wider applicable pH range from 3.5 to 6.5 for lead(II) uptake. The final pH values at equilibrium after adsorption were lower than the initial pH value, indicating that the ion-exchange process was involved in the adsorption. This is also confirmed by the result that the increase of acidic surface groups favored the adsorption process. Thermodynamic study indicated that the adsorption was a spontaneous and endothermic process.

Lead(II) adsorption from aqueous solutions by raw and activated charcoals of Melocanna baccifera Roxburgh (bamboo)--a comparative study

Melocanna baccifera (Poaceae) is the most abundant and economically important non-timber product in state of Mizoram, India. The communities of the region use this potential resource in many ways, charcoal production is one of them. Bamboo charcoal has application in food, pharmaceutical and chemical industries. Activated charcoal was prepared from M. baccifera charcoal by chemical pretreatment in order to make better use of this abundant biomass material. Batch experiments were conducted under varying range of pH (2.0-6.0), contact time (15-360 min) and metal ion concentrations (50-90 mg L(-1)). The optimum conditions for lead biosorption are almost same for M. baccifera raw charcoal (MBRC) and M. baccifera activated charcoal (MBAC)-pH 5.0, contact time 120 min, adsorption capacity q(max) 10.66 mg g(-1) and 53.76 mg g(-1), respectively. However, the biomass of MBAC was found to be more suitable than MBRC for the development of an efficient adsorbent for the removal of lead(II) from aqueous solutions. FTIR analysis revealed that -OH, C-H bending, C=O stretching vibration and carbonyl functional groups were mainly responsible for Pb(II) biosorption. Thus, this study demonstrated that both the charcoal biomass could be used as adsorbents for the treatment of Pb(II) from aqueous solution.

Adsorptive removal of Pb(II) by activated carbon prepared from Spartina alterniflora: equilibrium, kinetics and thermodynamics

Low-cost activated carbon was prepared from Spartina alterniflora by phosphoric acid activation for the removal of Pb(II) from dilute aqueous solution. The effect of experimental parameters such as pH, initial concentration, contact time and temperature on the adsorption was studied. The obtained data were fitted with the Langmuir and Freundlich equations to describe the equilibrium isotherms. The kinetic data were fitted with the Lagergren-first-order, pseudo-second-order and Elovich models. It was found that pH played a major role in the adsorption process. The maximum adsorption capacity for Pb(II) on S. alterniflora activated carbon (SAAC) calculated from Langmuir isotherm was more than 99 mg g(-1). The optimum pH range for the removal of Pb(II) was 4.8-5.6. The Freundlich isotherm model was found to best describe the experimental data. The kinetic rates were best fitted to the pseudo-second-order model. Thermodynamic study showed the adsorption was a spontaneous exothermic process.

Studies of lead retention from aqueous solutions using iron-oxide-coated sorbents

In this research, experiments were conducted to study Pb(2+) sorption onto engineered iron-oxide-coated sand (IOCS) and iron-oxide-coated crushed brick (IOCB), as well as onto naturally iron-oxide-coated sand (NIOCS). Optical and scanning electron microscopy (SEM) analyses were realised to investigate the surface properties and morphology of the coated sorbents. Infrared spectroscopy and X-ray diffraction techniques were also used to characterise the sorbent structures. Adsorption of lead from synthetic aqueous solutions was investigated by batch experiments. Results show that adsorption is slightly dependent on pH. The maximum adsorption capacity obtained at pH 6 was 5, 5.5 and 2.9 mg g(-1) for IOCS, IOCB and NIOCS, respectively. Both Freundlich and Langmuir isotherms can describe experimental data. The influence of temperature on the adsorption process was also evaluated. Results indicated that adsorption of Pb(2+) on the three sorbents is endothermic. The thermodynamic parameters (DeltaG(degrees), DeltaH(degrees) and DeltaS(degrees)) for Pb(2+) sorption on all considered sorbents were also determined from the temperature dependence. All considered sorbents could be an alternative emerging technology for water treatment without any side effects or treatment process alterations. However, IOCB has the best performances due to its greater capacity for the retention of lead.

Oxidative decolorization of methylene blue using pelagite

Pelagite generally has large surface area and high adsorbing and oxidizing reactivity due to highly amorphous nature, and high reducing potential of Mn (hydro)oxide phases present in it. In the present study, pelagite, collected from the East Pacific Ocean, was tested as a potential oxidant for decolorization of methylene blue (MB) in a batch system under air-bubbling and motor-stirring conditions. The effects of suspension pH (3.0-10.0), MB concentration (10-100 mgL(-1)) and loading (0.2-3.0 gL(-1)), and particle size (100-200 mesh) of pelagite on kinetics of MB decolorization were assessed. Results show that in typical concentration range of dye wastewaters (10-50 mgL(-1)), pelagite can be used as a highly efficient material for oxidative degradation of MB. MB decolorization was through a surface mechanism, that is, formation of surface precursor complex between MB and surface bound Mn(III, IV) center, followed by electron transfer within the surface complex. Iron (hydro)oxide phases present in the pelagite did not play an important role in MB decolorization. Suspension pH exerted double-edged effects on MB decolorization by influencing the formation of surface precursor complex, and reducing potential of the system. Kinetic rate of MB decolorization is directly proportional to saturation degree of available reaction sites by MB adsorption. At the initial and later stages, the kinetics for MB decolorization with respect to MB concentration, pelagite loading, and particle size could be described separately using two pseudofirst rate equations, except at very high pelagite loading (3.0 mgL(-1)). Accumulation of Mn(2+) and probably some organic intermediates exerted marked inhibitory effect on MB decolorization. Vigorous dynamic condition was favorable for MB decolorization. The presence of oxygen could enhance MB decolorization to a limited extent.

Adsorption of some bivalent heavy metal ions from aqueous solutions by manganese nodule leached residues

The leached residue, generated after selective extraction of Cu, Ni, and Co in sulfur dioxide-ammonia leaching of manganese nodules, was characterized and batch isothermal adsorption experiments were conducted at ambient temperature to evaluate the effectiveness of the water-washed leached residue for removal of different bivalent metal ions from aqueous synthetic solutions. The effects of pH, initial metal ion concentrations, amount of adsorbent, interfering ions, and heat treatment were also investigated. The uptake of metal ions increased with increasing pH. Under identical conditions the adsorption capacity increased in the order Cd(2+)<Cu(2+)<Pb(2+). The adsorption kinetics was found to follow a first-order rate expression and the experimental equilibrium adsorption data fitted reasonably well to both Langmuir and Freundlich isotherm models. Various metal ions present in the leached residue were found to be released during adsorption of heavy metals, which decreased with increased pH and were practically negligible at pH approximately 6.0. Desorption of adsorbed metal ions from metal-loaded leached residue and its regeneration ability were also studied. The results obtained could be useful for considering the leached manganese nodules residue as adsorbent for removal of heavy metal ions from contaminated water bodies.

Adsorption and redox reactions of heavy metals on Fe–Mn nodules from Chinese soils

Adsorption of heavy metals and redox reactions of Cr(W) ions on Fe-Mn nodules from five soils of China were investigated by chemical analysis, equilibrium adsorption/redox, and X-ray photoelectron spectroscopy (XPS). Results show that Mn is mainly present as Mn(3+) and Mn(4+) forms in Fe-Mn nodules. The maximum adsorption amounts for different heavy metal ions follow the order Pb(2+) approximately Cu(2+)>Zn(2+)>Co(2+)>Ni(2+)>Cd(2+). The adsorption capacity for heavy metals by Fe-Mn nodules from calciaquert in Shandong province (N5-1) is the highest, while that from hapludalf in Shandong province (N6-1) is the lowest. About 44-100% of the heavy metals adsorbed on Fe-Mn nodules were dissolved in 0.1 mol/L hydroxylamine hydrochloride (HAHC). The maximum amounts of Cr(VI) production by Fe-Mn nodules follow the order of N1-1 (69 mmol/kg)>N4-1 (57 mmol/kg)>N2-1 (52 mmol/kg)>N5-1 (44 mmol/kg). Based on the content of MnO(2) in Fe-Mn nodules dissolved in HAHC, the amount of Cr(VI) production by Mn oxides in N1-1, N2-1, N4-1, and N5-1 is 326, 624, 726, and 482 mmol/kg (MnO(2)), respectively. We propose that the amounts of Cr(VI) production through oxidation Cr(III) by Mn oxides are related to the types of Mn oxides in Fe-Mn nodules.