EDTA-based adsorbents for the removal of metal ions in wastewater

Corrosion-resistant omniphobic coating for low-carbon steel substrates using silica layers enhanced with ethylenediamine tetraacedic acid

The present work develops a highly liquid repellent, i.e. omniphobic, coating designed specifically for metallic substrates like low carbon steels and evaluates its potential as a barrier to corrosion. Polydimethylsiloxane (PDMS) chains are grafted to an intermediary silica layer via the hydrolysis and polycondensation of a difunctional chlorosilane monomer, resulting in a contact angle hysteresis of ∼3° when deposited on unpolished low carbon steel substrates. However, the use of chlorosilanes to fabricate the omniphobic PDMS can corrode steel. To circumvent this, the coating uses a phosphate buffer solution to partially neutralize the silica precursor solution, and ethylenediamine tetraacedic acid (EDTA) to passivate any released Fe ions. The inhibition of corrosion is evidenced visually and by unchanging surface metrology parameters even after two months following coating deposition. Potentiodynamic polarization data indicate that the omniphobic layer provides a barrier to water ingress, as evidenced by a current density of ∼10-6 A cm-2, two orders of magnitude lower than the steel coated with the silica but without the PDMS chains. Electrochemical impedance spectroscopy data indicates the absence of an inductive loop (i.e. no ongoing corrosion) and a high polarization resistance of 40 000 Ω cm2 for the omniphobic coating. This work not only indicates that omniphobic grafted polymer chains like PDMS exhibit anti-corrosion properties, but also provides a method for depositing such coatings onto metals without corroding the substrate, even when using chlorosilane precursors that evolve hydrochloric acid.

Carbon-Supported Single Fe/Co/Ni Atom Catalysts for Water Oxidation: Unveiling the Dynamic Active Sites

Extensive research has been conducted on carbon-supported single-atom catalysts (SACs) for electrochemical applications, owing to their outstanding conductivity and high metal atom utilization. The atomic dispersion of active sites provides an ideal platform to investigate the structure-performance correlations. Despite this, the development of straightforward and scalable synthesis methods, along with the tracking of the dynamic active sites under catalytic conditions, remains a significant challenge. Herein, we introduce a biomass-inspired coordination confinement strategy to construct a series of carbon-supported SACs, incorporating various metal elements, such as Fe, Co, and Ni. We have systematically characterized their electronic and geometric structure using various spectroscopic and microscopic techniques. Through in situ X-ray absorption spectroscopy (XAS), atomic scanning transmission electron microscopy (STEM), and electron paramagnetic resonance (EPR) analyses, it is demonstrated that the single atoms undergo structural rearrangement to form amorphous (oxy)hydroxide clusters during oxygen evolution reaction (OER), where the newly formed oxygen-bridged dual metal M─O─M or M─O─M' (M/M' = Fe, Co, Ni) moieties within these clusters play key role in the OER performance. This work provides essential insights into tracking the actual active sites of SACs during electrochemical OER.

Selective Trapping of In(III) Ions under σ-π* Bond Synergistic Effects by Modulating Lewis Basicity of Capture Sites on Nanofibers

Effectively selective recovery and separation of indium from alternative resources are of great environmental and economic significance. Although adsorption plays a critical role in this process, the design of highly selective capture sites remains a great challenge. Inspired by molecular orbital theory and hard and soft acids and bases theory (HSAB), we recognize that the nonequivalent orbital hybridization of In(III) ions renders them susceptible to deformation, exhibiting softer Lewis acidity. Herein, the thioacetamide-modified nanofiber (TAANF), with the O═C─NH─C═S as the capture sites, was prepared through an electrospinning technique combined with chemical modification. As expected, the O═C─NH─C═S exhibits softer Lewis basicity via modulated Lewis basicity of C═S by C═O, which better matches the Lewis acidity of In(III) ions to improve affinity. Adsorption studies showed that TAANF exhibited excellent properties for In(III) ions, especially in terms of selectivity; the selectivity coefficients range from 20 to 276 for K(I), Ca(II), Na(I), Mg(II), Mn(II), Zn(II), and Fe(II) ions in a multicomponent system. Furthermore, the capture mechanism indicates that In(III) ions not only can accept electrons from capture sites but also donate rich d2 orbit electrons to the π orbitals of capture sites, as demonstrated by XAFS, XPS, and DFT. This enables selective capture of In(III) ions by forming a stable six-membered ring under the synergistic effect of σ and feedback π bonds (σ-π*). Finally, this work provides a strategy to design highly selective capture sites and holds promise for recovering In(III) ions from alternative sources.

Development of a Treatment System of Water with Cr (VI) Through Models Using E. crassipes Biomass with Iron Chloride

In the context of critical water quality issues, there is a pressing need for more pragmatic approaches to water research. Adsorbent biomass, derived from abundant and effective natural sources, holds considerable promise as a solution. E. crassipes, a type of plant biomass, has emerged as a particularly promising material due to its high adsorption capacity. When combined with iron chloride, this capacity is significantly enhanced, and the addition of EDTA is essential for the reuse of treated water. The economic viability of this material in water treatment has been thoroughly evaluated, and the project was developed with the aim of building treatment systems using E. crassipes biomass in conjunction with iron chloride. The development process involved the creation of a special material composed of 85% dried and ground E. crassipes and 15% iron chloride. The process was scaled up with the most effective biomass for treatment and subsequent elutions with EDTA. The outlet conditions, the quantity of pollutant removed, and the treated volume were established, and subsequently the extraparticle diffusion constant Kf, the intraparticle diffusion constant, and the characteristic isotherm were determined. The identification of the intraparticle diffusion model, Ks, was made possible by the results of the model, which indicated the specific route for the construction of a pilot-scale treatment system. The pilot-scale prototype was constructed using 1000 g of EC (2) of biomass (850 g of E. crassipes and 150 g of chloride of iron). The prototype developed in the present investigation could be used to treat effluents contaminated with heavy metals, especially chromium, and is an advanced environmental research project that contributes to the improvement of water quality.

Facile synthesis of high-swelling cyclodextrin polymer for sustainable water purification

Porous materials are widely used in the adsorption field to sequester pollutants to address the global sustainable water security and water scarcity concerns. However, there are still challenges that limit their industrial application, especially the required rational design and construction of porous structures. Here, we report a high-swelling cyclodextrin polymer (His-CDP) that is facilely synthesized without additional design and templates, to achieve high affinity, non-specific and rapid adsorption of pollutants. His-CDP rapidly swells in water with high swelling ratio (706 %), and swelling results in a significant increase in the specific surface area (from 38 m2∙g-1 of dry state to 562 m2∙g-1 of wet state) and abundant adsorption sites. The adsorption rates of His-CDP for methylene blue (MB), bisphenol A (BPA), and copper ion (Cu2+) are 0.304 g∙mg-1∙min-1, 0.370 g∙mg-1∙min-1, and 0.117 g∙mg-1∙min-1, respectively, which are 106-571 times, 5-15 times, and 36-58 times higher than those of activated carbons and low-swelling cyclodextrin polymer. The maximum adsorption capacities of His-CDP for MB, BPA, and Cu2+ are 1.06 mol∙g-1, 0.35 mol∙g-1, and 1.95 mol∙g-1, respectively. His-CDP has high stability, good reproducibility, cost-effective regeneration, and is expected to be produced on a large scale. As a demonstration application, we demonstrate that His-CDP outperforms activated carbons in rapid, high-capacity purification of tap water, treatment of industrial wastewater and remediation of polluted surface water. Our findings open the way for the application of high-swelling polymers in sustainable water purification.

A High-Performance Electrochemical Sensor Based on Ni-Pt Bimetallic Nanoparticles Doped Metal Organic Framework ZIF-8 for the Detection of Dopamine

In this paper, microporous Zn-based zeolitic imidazolate framework with the sodalite cage structure (SOD-ZIF-8) was synthesized by the solvothermal method. Powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and N2 adsorption were employed to characterize the synthesized material. An ultra-sensitive electrochemical sensor based on highly dispersed bimetallic Ni-Pt nanoparticles immobilized on zeolitic metal-organic framework ZIF-8 for dopamine quantification is introduced for the first time. The as-prepared Ni-Pt@ZIF-8 composite was deposited onto a glassy carbon electrode (GCE), serving as a sensor that exhibits superior properties for the detection of dopamine (DA). A Box-Behnken design was employed, and response surface methodology (RSM) was applied to investigate the impact of various experimental parameters on dopamine detection. The parameters optimized in this study included pH, drying time (hours), drop volume for deposition (μL), and accumulation time (minutes). The Box-Behnken experimental design enabled the systematic optimization of these factors to enhance the sensor's performance. Benefiting from the synergy of ZIF-8 and Ni-Pt bimetallic nanoparticles, the Ni-Pt@ZIF-8 composite exhibited high sensitivity towards dopamine, achieving a low detection limit of 1.0 nM. The sensor's linear response to dopamine (1 nM to 10 μM), resistance to interference, and high recovery in human serum, coupled with its simple fabrication, make it a promising tool for real-world dopamine detection.

Leaching law of heavy metals in coal gangue: A combination of experimental optimization and simulation

Coal gangue, a solid waste generated during coal mining and washing processes, has caused significant environmental burdens in China. This study aims to optimize and investigate the leaching mechanisms of heavy metals, such as Pb, Zn, and Cu, in coal gangue. The effectiveness of different eluents in removing heavy metals from coal gangue was evaluated by combining experimental methods with software simulations. The leaching conditions (EDTA-2Na concentration of 5 g/L, pH 3, solidliquid ratio of 1:10, leaching time of 4 h, 300 r/min) were optimized to achieve efficient and economical removal of heavy metals. Box-Behnken Design was used to show the key factors of eluant concentration and solid-liquid ratio. The leaching amounts of Pb, Zn, and Cu from coal gangue using EDTA-2Na as a leaching agent were 86 mg/kg, 430 mg/kg, and 66 mg/kg, respectively. The release mechanism and kinetic behavior of heavy metals in the leaching process were studied. The study provided information about leaching mechanisms of heavy metals from coal gangue by experiments and simulations of Visual MINTEQ and DFT that EDTA-2Na enhanced the leaching of heavy metals from coal gangue by enhancing ion exchange and complexation.

Laser-Induced Graphene for Electrochemical Sensing of Antioxidants in Biodiesel

Synthetic antioxidants are often introduced to biodiesel to increase its oxidative stability, and tert-butyl hydroquinone (TBHQ) has been selected due to its high efficiency for this purpose. The monitoring of antioxidants in biodiesel therefore provides information on the oxidative stability of biodiesels. Herein, a laser-induced graphene (LIG) electrode is introduced as a new sensor for detecting tert-butyl hydroquinone (TBHQ) in biodiesel samples. An infrared CO2 laser was applied for LIG formation from the pyrolysis of polyimide (Kapton). Based on the voltammetric profile of a reversible redox probe, the fabrication of LIG electrodes was set using 1.0 W power and 40 mm s-1 speed, which presented an electroactive area of 0.26 cm2 (higher than the geometric area of 0.196 cm2). Importantly, lower engraving speed resulted in higher electroactive area, probably due to a more efficient graphene formation. Scanning-electron microscopy and Raman spectroscopy confirmed the creation of porous graphene induced by laser. The sensing platform enabled the differential-pulse voltammetric determination of TBHQ from 5 and 450 μmol L-1. The values of detection limit (LOD) of 2 μmol L-1 and RSD (relative standard deviation) of 2.5% (n = 10, 10 μmol L-1 of TBHQ) were obtained. The analysis of spiked biodiesel samples revealed recoveries from 88 to 106%. Also, the method provides a satisfactory selectivity, as it is free of interference from metallic ions (Fe3+, Mn2+, Cr2+, Zn2+, Pb2+, and Cu2+) commonly presented in the biofuel. These results show that LIG electrodes can be a new electroanalytical tool for detecting and quantifying TBHQ in biodiesel.

Reducing the Radioactive Surface Contamination Level of Cobalt-60-Contaminated Material with PVA-Glycerol-EDTA Combination Gel

Decommissioning of nuclear facilities can be performed in stages. One of the stages and processes in decontamination is the decontamination process before dismantling or facility area recovery activities. Decontamination can be performed using various methods, primarily physical and chemical. One chemical method involves using a gel made of polymers for decontamination. In this study, a gel consisting of a mixture of 15 g polyvinyl alcohol (PVA), 15 mL of glycerol, and 2 g Na-EDTA was dissolved in 100 mL. The three materials were dissolved in hot conditions until they dissolved, and a gel was formed. The formed gel was applied to the material contaminated by Co-60 with a radioactivity of 81 µCi, as much as 5 µL. The decontamination radioactive efficiency test results range from 53% to 98%, with the highest decontamination efficiency observed on glass media. This study also showed that higher EDTA concentrations can increase the ability of the PVA-glycerol gel to absorb and bind Co. This study also found that decontamination efficiency was influenced by the type of contaminated material and the concentration of EDTA. It can be concluded that gels with a composition of PVA, glycerol, and EDTA can reduce the level of contamination on the surface of materials made of glass, ceramics, and metal plates.

Use of Ni/CNT Particles as Additive Fillers in Ebonite Bipolar Plates for Proton-Exchange Membrane Fuel Cells

Composite-based bipolar plates are a chance to substitute graphite and metal bipolar plates because of their corrosion resistance and better chemical and mechanical properties, but they still have various electrical conductivity properties. One of the problems is the loading of filler that depends on matrix types which will affect the electrical conductivity of bipolar plates; ebonite has potential as a matrix in composite bipolar plates because it is obtained from elastomer or rubber. In this work, nickel and carbon nanotubes (CNT) that have a high electrical conductivity will be investigated as additive fillers on graphite particles to enhance the electrical conductivity of ebonite bipolar plates. The formulation and characterization of ebonite bipolar plates with graphite and graphite Ni/CNT and their various contents are the main objectives of this research. Characterization by scanning electron microscopy (SEM) for identification and morphology of compounds and ebonite bipolar plates and Raman spectroscopy for identification of the type carbon in Ni/CNT was performed. Some tests such as bending/flexural tests, corrosion tests, and resistance testing for interfacial contact resistance were conducted to study the properties and optimum of the composite materials. In this research, Ni/CNT particles were added as additive fillers with graphite to enhance the electrical conductivity of fillers in ebonite bipolar plates of proton-exchange membrane fuel cells and their impacts were studied. By through-plane testing, graphite fillers were added in ebonite bipolar plates with 65-75% w/w content, achieving electrical conductivity values from 22.3 to 34 S/cm. This is still below the technical target set by the US DOE for composite bipolar plates. But by adding 30% Ni/CNT filler contents in ebonite bipolar plates at various filler contents from 65% to 75% w/w, one can achieve electrical conductivities from 104.35 to 165.52 S/cm. Only 65% w/w filler with 30% Ni/CNT can meet the technical targets such as a bending/flexural test value of 25.58 N/mm2, a corrosion test value of 0.894 μA/cm2 (I corr), and an interfacial contact resistance value of 3.09 mΩ cm2. Further improvements are needed based on fuel cell applications, as indicated by some additional data that did not meet technical targets.

Defect-Engineered MOF-801/Sodium Alginate Aerogel Beads for Boosting Adsorption of Pb(II)

Metal-organic frameworks (MOFs) are attractive adsorbents for heavy metal capture due to their superior stability, easy modification, and adjustable pore size. However, their inherent microporous structure poses challenges in achieving a higher adsorption capacity. Defect engineering is considered a simple method to create hierarchical MOFs with larger pores. Here, we employed l-aspartic acid as a mixed linker to bind Zr4+ clusters in competition with fumaric acid of MOF-801 to create defects, and the pore size was increased from 4.66 to 15.65 nm. Mercaptosuccinic acid was subsequently used as a postexchange ligand to graft the resultant MOF-801 by acid-ammonia condensation to further expand the pore size to 22.73 nm. Notably, the -NH2, -COOH, and -SH groups contributed by these two ligands increased the adsorption sites for Pb(II). The obtained defective MOF-801 with larger pores was thereafter loaded onto sodium alginate to form aerogel beads as adsorbents, and an adsorption capacity of 375.48 mg/g for Pb(II) was achieved, which is ∼51 times that of pristine MOF-801. The aerogel beads also exhibited outstanding reusability with a removal efficiency of ∼90.23% after 5 cycles of use. The adsorption mechanism of Pb(II) included ion-exchange interaction, as well as chelation interactions of Pb-O, Pb-NH2, and Pb-S. The versatile combination of defect engineering and composite beads provides novel inspirations for MOF modification for boosting heavy metal adsorption.

Fabrication of a novel magnetic carbon nanotube coated with polydopamine modified with EDTA for removing Cd2+ and Pb2+ ions from an aqueous solution

This work demonstrates the preparation of a new, effective, and reusable magnetic adsorbent by functionalizing dopamine with ethylenediaminetetraacetic dianhydride and polymerizing it on the surface of magnetic carbon nanotubes (EDTA@PD-CNT/Fe3O4). The adsorbent was analyzed using XRD, FT-IR, Zeta potential, FE-SEM, EDX, BET, TGA, DTA, and VSM. The synthesized adsorbent was used to remove lead and cadmium ions from aqueous solution. The adsorption process was improved by optimizing key parameters such as pH, adsorbent dosage, contact time, and ion concentration. For both ions, the thermodynamic data of the processes and adsorption kinetics were examined. Analyzing the experimental data revealed that the Langmuir isotherm was the most appropriate model, and the examination of adsorption kinetics showed a pseudo-second-order equation. The adsorption process by the EDTA@PD-CNT/Fe3O4 adsorbent was spontaneous and endothermic, according to the thermodynamic data, for Cd2+ and Pb2+, the highest adsorption capacities were found to be 204.54 mg g-1 and 376.48 mg g-1, respectively.

Role of EDTA protonation in chelation-based removal of mercury ions from water

A robust method of hazardous metal ion removal from an aqueous environment involves the use of chelating agents, such as ethylenediaminetetraacetic acid (EDTA). Here, we focus on mercury (Hg2+) uptake by EDTA using both molecular dynamics and density functional theory simulations. Our results indicate that the deprotonation of the EDTA carboxylate groups improves the localization of negative charge on the deprotonated sites. This mechanism facilitates charge transfer between the metal ions and EDTA, and provides a stronger and more stable EDTA-Hg2+ complex formation improving the efficiency of the chelation process. The best metal removal conditions are achieved using the fully deprotonated form of EDTA, which naturally occurs at pH levels above 3.

Strong, anti-swelling, and biodegradable seaweed-based straws with surface mineralized CaCO3 armor

While the extensive utilization of disposable plastic straws has resulted in significant environmental issues such as microplastics and soil and ocean pollution, the quest for alternative straws for versatile use remains a formidable challenge. Here, drawing inspiration from naturally water-resistant materials such as bones and sea urchins, we have developed seaweed-based straws with significantly improved water resistance and mechanical strength via in-situ mineralization of CaCO3 on their surfaces. Specifically, the COO- groups on the G (α-L-guluronate) blocks of alginate were employed to establish a robust cross-linked network, while the COO- groups on the M (β-D-mannuronate) blocks attracted free Ca2+ through electrostatic forces, thereby promoting CaCO3 nucleation. This effectively prevents COOH groups from hydrating, reducing swelling, and results in the fabrication of nano- to micron-sized CaCO3 particles that reinforce the structure without compromising the cross-linked network. Compared with the control group, the S5% sample (prepared with 5 % Na2CO3 solution) exhibited a 102 % increase in water contact angle, a 35 % decrease in swelling degree, and a 35.5 % and 37.5 % increase in ultimate flexural and tensile stress, respectively. Furthermore, the potential use of these straws as a waste for heavy metal adsorption was investigated, addressing environmental concerns while demonstrating economic feasibility.

EDTA-Assisted MPT-MS for Trace Analysis of Heavy Metals in Fireworks

A novel method was developed for the rapid detection of heavy metals in firework solutions with high sensitivity and minimal pretreatment by enriching them with ethylenediaminetetraacetic acid (EDTA) reagent and analyzing them using microwave plasma torch mass spectrometry (MPT-MS). Quantitative results showed that the limits of detection and quantification for heavy metals (Pb, Ba, Sr, and Ag) ranged from 0.05 to 0.25 and 0.38 to 0.71 μg·L-1, respectively. The linear dynamic ranges covered at least two orders of magnitude, with correlation coefficients exceeding 0.99. Fireworks from five regions in China were also analyzed quantitatively, detecting heavy metals including Pb, Ba, Sr, and Ag, with recovery rates ranging from 87.9% to 107.5%. Good separation between the firework samples from different regions was achieved by using element ratios and principal component analysis (PCA). These results from the preliminary study showed that the EDTA-assisted MPT-MS combined with PCA is a powerful tool for characterizing firework samples and tracing them back to their sources, which is valuable to effectively regulate and manage banned fireworks.

The Chemistry of Chelation for Built Heritage Cleaning: The Removal of Copper and Iron Stains

Chelators are widely used in conservation treatments to remove metal stains from marble, travertine, and limestone surfaces. In the current review the chemical aspects underlying the use of chelators for the removal of copper and iron stains from built heritage are described and clear criteria for the selection of the most efficient stain removal treatment are given. The main chelator structural features are outlined and the operating conditions for effective metal stain removal (pH, time of application, etc.) discussed, with a particular emphasis on the ability to form stable metal complexes, the high selectivity towards the metal that should be removed, and the high sustainability for the environment. Dense matrices often host chelators for higher effectiveness, and further research is required to clarify their role in the cleaning process. Then, relevant case studies of copper and iron stain removal are discussed. On these bases, the most effective chelators for copper and stain removal are indicated, providing chemists and conservation scientists with scientific support for conservation operations on stone works of art and opening the way to the synthesis of new chelators.

Highly sensitive and accurate measurement of underivatized phosphoenolpyruvate in plasma and serum via EDTA-facilitated hydrophilic interaction liquid chromatography-tandem mass spectrometry

Phosphoenolpyruvate (PEP) is an essential intermediate metabolite that is involved in various vital biochemical reactions. However, achieving the direct and accurate quantification of PEP in plasma or serum poses a significant challenge owing to its strong polarity and metal affinity. In this study, a sensitive method for the direct determination of PEP in plasma and serum based on ethylenediaminetetraacetic acid (EDTA)-facilitated hydrophilic interaction liquid chromatography-tandem mass spectrometry was developed. Superior chromatographic retention and peak shapes were achieved using a zwitterionic stationary-phase HILIC column with a metal-inert inner surface. Efficient dechelation of PEP-metal complexes in serum/plasma samples was achieved through the introduction of EDTA, resulting in a significant enhancement of the PEP signal. A PEP isotopically labelled standard was employed as a surrogate analyte for the determination of endogenous PEP, and validation assessments proved the sensitivity, selectivity, and reproducibility of this method. The method was applied to the comparative quantification of PEP in plasma and serum samples from mice and rats, as well as in HepG2 cells, HEK293T cells, and erythrocytes; the results confirmed its applicability in PEP-related biomedical research. The developed method can quantify PEP in diverse biological matrices, providing a feasible opportunity to investigate the role of PEP in relevant biomedical research.

A new strategy for utilization of gasification ash: Manganese oxides-modified activated carbon for efficient copper citrate removal

To address the challenges posed by solid waste generated from coal gasification ash, a pyrolysis self-activation method was employed to prepare activated carbon by gasification ash, followed by the modification with manganese oxide to enhance its adsorption performance. Subsequently, the removal efficiency and mechanism for copper citrate were investigated. The results demonstrated the successful preparation of manganese oxides modified gasification ash-derived activated carbon (GAC-MnOx), exhibiting a specific surface area of 158.3 m2/g and a pore volume of 0.1948 cm³/g. The kinetic process could be described by the pseudo-second-order kinetic model (R2 = 0.958). High removal efficiency and low concentration of dissolved Mn were observed within the pH range of 3-10, where the adsorption capacity of GAC-MnOx for copper citrate exhibited an inverse relationship with pH. Notably, the fitting results of the Langmuir model demonstrated that the maximum adsorption capacity of GAC-MnOx for copper citrate is determined to be 7.196 mg/g at pH 3. The adsorption capacity of GAC-MnOx was found to be significantly reduced to 0.26 mg/g as the pH decreased below 2, potentially attributed to the dissolution of Mn. The findings of the Dual-Mode model demonstrated that the copper citrate removal mechanism by GAC-MnOx involved both surface adsorption and precipitation processes as follows: the porous structure of activated carbon enables physical adsorption of copper citrate, the MnOx or oxygen-containing functional groups establish chemical bonds with copper citrate and subsequently precipitate onto the surface of the adsorbent. The physical adsorption remains predominant in the removal of copper citrate, despite a gradual decrease in its proportion with increasing pH and equilibrium concentrations. Moreover, the X-ray photoelectron spectroscopy results indicated that copper citrate might be oxidized by MnOx to release copper ions and be retained on the surface of the adsorbent, meaning the adsorption efficiency of Cu(II)-Cit by GAC was enhanced through MnOx oxidation. This study could provide a new strategy for the high-value resource utilization of gasification ash.

Oxygen-Centered Organic Radicals-Involved Unified Heterogeneous Self-Fenton Process for Stable Mineralization of Micropollutants in Water

Removing organic micropollutants from water through photocatalysis is hindered by catalyst instability and substantial residuals from incomplete mineralization. Here, a novel water treatment paradigm, the unified heterogeneous self-Fenton process (UHSFP), which achieved an impressive 32% photon utilization efficiency at 470 nm, and a significant 94% mineralization of organic micropollutants-all without the continual addition of oxidants and iron ions is presented. In UHSFP, the active species differs fundamentally from traditional photocatalytic processes. One electron acceptor unit of photocatalyst acquires only one photogenerated electron to convert into oxygen-centered organic radical (OCOR), then spontaneously completing subsequent processes, including pollutant degradation, hydrogen peroxide generation, activation, and mineralization of organic micropollutants. By bolstering electron-transfer capabilities and diminishing catalyst affinity for oxygen in the photocatalytic process, the generation of superoxide radicals is effectively suppressed, preventing detrimental attacks on the catalyst. This study introduces an innovative and cost-effective strategy for the efficient and stable mineralization of organic micropollutants, eliminating the necessity for continuous chemical inputs, providing a new perspective on water treatment technologies.

Core-shell design of UiO66-Fe3O4 configured with EDTA-assisted washing for rapid adsorption and simple recovery of heavy metal pollutants from soil

The coupling of washing with adsorption process can be adopted for the treatment of soils contaminated with heavy metals pollution. However, the complex environment of soil and the competitive behavior of leaching chemicals considerably restrain adsorption capacity of adsorbent material during washing process, which demands a higher resistance of the adsorbents to interference. In this study, we synthesized strongly magnetic, high specific surface area (573.49 m2/g) UiO66 composites (i.e., UiO66-Fe3O4) using hydrothermal process. The UiO66-Fe3O4 was applied as an adsorbent during the ethylene diamine tetraacetic acid (EDTA)-assisted washing process of contaminated soil. The incorporation of UiO66-Fe3O4 results in rapid heavy metal removal and recovery from the soil under low concentrations of washing agent (0.001 mol/L) with reduced residual heavy metal mobility of soil after remediation. Furthermore, UiO66-Fe3O4 can quickly recollect by an external magnet, which offers a simple and inexpensive recovery method for heavy metals from contaminated soil. Overall, UiO66-Fe3O4 configuration with EDTA-assisted washing process showed opportunities for heavy metals contaminated sites.

Phenol-Formaldehyde/Pyrazole Composite: Synthesis, Characterization, and Evaluation of its Chromate Removal Efficiency

In this study, we report the successful synthesis of a phenol-formaldehyde-pyrazole (PF-PYZ) compound through the surface functionalization of phenol-formaldehyde (PF) with pyrazole (PYZ). The resulting mixture was subjected to comprehensive characterization using a range of analytical techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The newly synthesized PF-PYZ material effectively removes Cr(VI) ions. Notably, a substantial elimination efficiency of 96% was achieved after just 60 min of contact time. The strategic incorporation of pyrazole (PYZ) as the principal functionalizing agent contributed to this exceptional performance. Notably, the functionalized PYZ sites were strategically positioned on the surface of PF, rendering them readily accessible to metal ions. Through rigorous testing, the optimal sorption capacity of PF-PYZ for Cr(VI) ions was quantified at 0.872 mmol Cr(VI)/g, highlighting the material's superior adsorption capabilities. The practical utility of PF-PYZ was further established through a reusability test, which demonstrated that the chromate capacity remained remarkably stable at 0.724 mequiv Cr(VI)/g over 20 consecutive cycles. This resilience underscores the robustness of the resin, indicating its potential for repeated regeneration and reuse without a significant capacity loss. Our work presents a novel approach to functionalizing phenol-formaldehyde with pyrazole, creating PF-PYZ, a highly efficient material for removing Cr(VI) ions. The compound's facile synthesis, exceptional removal performance, and excellent reusability collectively underscore its promising potential for various water treatments, especially oil field and environmental remediation applications.

Polycarboxylate functionalized magnetic nanoparticles Fe3O4@SiO2@CS-COOH: Preparation, characterization, and immobilization of bovine serum albumin

Magnetic nanoparticles with increasing superparamagnetism and magnetic targeting have found widespread application in fields such as food and medicine. In this study, polycarboxylated magnetic nanoparticles (Fe3O4@SiO2@CS-COOH) were prepared by surface functionalizing iron tetraoxide (Fe3O4) nanoparticles with ethylenediaminetetraacetic acid (EDTA) as a modifier. The appropriate degree of functionalization modification was obtained by adjusting the EDTA concentration and the ratio of cross-linking agents. The prepared magnetic nanoparticles were analyzed with structural and property characterization. The results showed that the Fe3O4@SiO2@CS-COOH magnetic nanoparticles prepared with 4 % EDTA and cross-linking agents at a molar ratio of 3:4 were uniform in particle size, with an average size of roughly 7 nm, and possessed an abundant carboxylate content (310.8064 μmol/g) and a high magnetization intensity (35.05 emu/g). As a model protein, bovine serum albumin (BSA) was immobilized on the surface of magnetic particles. The largest amount of immobilized protein was 500.4376 mg BSA/g at pH 4.0 and no extra salt ions. According to molecular docking simulations, its immobilization was due to the interaction of amino and carboxyl groups at the Fe3O4@SiO2@CS-COOH/BSA interface. Fe3O4@SiO2@CS-COOH possesses a large number of carboxyl groups, strong protein immobilization, and magnetic responsiveness, which may have potential applications in biomedical and food fields.

Performance and mechanism of amphiphilic polymeric chelator for enhanced removal of high concentrations of Cu(II) from wastewater

An amphiphilic polymeric chelator (APC16-g-SX) grafted with sodium xanthate (SX) groups was successfully prepared for the efficient removal of high concentrations of Cu(II) from wastewater. The ordinary polymeric chelator (PAM-g-SX) based on linear polyacrylamide (PAM) was also prepared for comparative studies. The polymeric chelators were characterized by Fourier transform infrared spectroscopy (FT-IR), solid-state nuclear magnetic resonance (13C-NMR), gel permeation chromatography (GPC), elemental analyzer, and scanning electron microscope (SEM). The chelating performance of these polymeric chelators was investigated, and the mechanism of APC16-g-SX for enhanced removal of Cu(II) from wastewater was proposed based on fluorescence spectroscopy, cryo-scanning electron microscope (Cryo-SEM), energy-dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS) tests. The results show that as the initial Cu(II) concentration in the wastewater increases, APC16-g-SX shows more excellent chelating performance than ordinary PAM-g-SX. For the wastewater with an initial Cu(II) concentration of 200 mg/L, the removal rate of Cu(II) was 99.82% and 89.34% for both 500 mg/L APC16-g-SX and PAM-g-SX, respectively. The pH of the system has a very great influence on the chelating performance of the polymeric chelators, and the increase in pH of the system helps to improve the chelating performance. The results of EDS and XPS tests also show that N, O, and S atoms in APC16-g-SX were involved in the chelation of Cu(II). The mechanism of enhanced removal of Cu(II) by APC16-g-SX can be attributed to the spatial network structure constructed by the self-association of hydrophobic groups that enhances the utilization of chelation sites.

Adsorption of lead ions from wastewater using electrospun zeolite/MWCNT nanofibers: kinetics, thermodynamics and modeling study

Heavy metal contamination in water is a serious environmental issue due to the toxicity of metals like lead. This study developed zeolite and multi-walled carbon nanotube (MWCNT) incorporated polyacrylonitrile (PAN) nanofibers via needleless electrospinning and examined their potential for lead ion adsorption from aqueous solutions. The adsorption process was optimized using response surface methodology (RSM) and artificial neural network (ANN) modeling approaches. The adsorbent displayed efficient lead removal of 84.75% under optimum conditions (adsorbent dose (2.21 g), adsorption time (207 min), temperature (48 °C), and initial concentration (62 ppm)). Kinetic studies revealed that the adsorption followed pseudo-first-order kinetics governed by interparticle diffusion. Isotherm analysis indicated Langmuir monolayer adsorption with improved 5.90 mg g-1 capacity compared to pristine PAN nanofibers. Thermodynamic parameters suggested the adsorption was spontaneous and endothermic. This work demonstrates the promise of electrospun zeolite/MWCNT nanofibers as adsorbents for removing lead from wastewater.

Staged purification of phosphogypsum using pH-dependent separation process

Phosphogypsum (PG) is an industrial by-product of the transformation of phosphate rocks. For decades, PG has been a source of environmental concern due to the massive amount produced thus far, i.e., 7 billion tons, with a current production rate of 200-280 million tons per year. Phosphate minerals contain various impurities that precipitate and concentrate within PG. These impurities hinder PG usability in various sectors. This paper aims to purify PG using an innovative process based on staged valorization of PG. Initially, PG dissociation by ethylenediaminetetraacetic acid (EDTA) was optimized. After screening of different parameters and monitoring the ionic conductivity of solutions, it was disclosed that a pH-dependent solubilization process in the presence of EDTA resulted in high solubility of PG, up to 11.82 g/100 mL at pH > 11. Subsequently, a recovery of the purified PG by selective precipitation of calcium sulfate dihydrate (CSD) from obtained filtrate through pH adjustment to 3.5 were investigated. An abatement of 99.34% Cr, 97.15% Cd, 95.73% P2O5, 92.75% Cu, 92.38% Al2O3, 91.16% Ni, 74.58% Zn, 72.75% F, 61.43% MgO, 58.8% Fe2O3, 56.97% K2O, and 55.41% Ba was achieved. The process relied on the variation of EDTA chelation properties towards monovalent, divalent, and trivalent cations at different pHs. According to the findings of this study, a staged purification process in the presence of EDTA is an effective method for removing impurities from the industrial PG.

Synthesis, Optimization, and Characterization of Cellulase Enzyme Obtained from Thermotolerant Bacillus subtilis F3: An Insight into Cotton Fabric Polishing Activity

The efficacy of 40 bacterial isolates obtained from hot spring water samples to produce cellulase enzymes was investigated. As a result, the strain Bacillus subtilis F3, which was identified using traditional and molecular methods, was selected as the most potent for cellulase production. Optimization was carried out using one-factor-at-a-time (OFAT) and BOX-Behnken Design to detect the best conditions for the highest cellulase activity. This was accomplished after an incubation period of 24 h at 45°C and pH 8, with an inoculum size of 1% (v/v), 5 g/l of peptone as nitrogen source, and 7.5 g/l of CMC. Moreover, the best concentration of ammonium sulfate for cellulase enzyme precipitation was 60% followed by purification using a dialysis bag and Sephadex G-100 column chromatography to collect the purified enzyme. The purified cellulase enzyme was characterized by 5.39-fold enrichment, with a specific activity of 54.20 U/mg and a molecular weight of 439 kDa. There were 15 amino acids involved in the purified cellulase, with high concentrations of 160 and 100 mg/l for glycine and proline respectively. The highest stability and activity of the purified cellulase was attained at pH 7 and 50°C in the presence of 150 ppm of CaCl2, NaCl, and ZnO metal ions. Finally, the biopolishing activity of the cellulase enzyme, as indicated by weight loss percentages of the cotton fabric, was dependent on concentration and treatment time. Overall, the thermotolerant B. subtilis F3 strain has the potential to provide highly stable and highly active cellulase enzyme for use in biopolishing of cotton fabrics.

Enhancement of heavy metals desorption from the soil by eddy deep leaching in hydrocyclone

An eddy deep leaching technology was developed in this paper to address the challenge of treating heavy metal contaminants in industrial mining areas. The desorption effect of As, Cd, Sb and Pb was investigated utilizing chemical leaching and physical eddy techniques. It was found that the heavy metals concentration increased with decreasing particle size. The highest proportion of Cd in the form distribution of soil was in the bound to iron and manganese oxides, while the maximum proportion of As, Sb and Pb were in the residual. The optimal solid-liquid ratio of the hydrocyclone was 1:20, and the corresponding separation efficiency and flow rate were 84.7% and 1.76 m3/hr, respectively. The grade efficiency of soil particle separation increases with particle size and exceeds 99% for particles above 1,000 µm. Leaching experiments have revealed that oxalic acid (OA) and a combination of oxalic acid and EDTA (OAPE) were more efficient than citric acid (CA) and a combination of citric acid and EDTA (CAPE) for the desorption of heavy metals, respectively. The comparison of OAPE and eddy leaching found that the latter improved the desorption efficiency by 9.4%, 7.5%, 7.2% and 7.8% for As, Cd, Sb and Pb compared to the former, respectively. The results demonstrated that the eddy leaching technique could further enhance the desorption efficiency of heavy metals. It is expected to provide technical support for soil remediation with reduced usage of leaching agents.

Advances in responses of microalgal-bacterial symbiosis to emerging pollutants in wastewater

Nowadays, emerging pollutants are widely used and exist in wastewater, such as antibiotics, heavy metals, nanoparticle and microplastic. As a green alternative for wastewater treatment, microalgal-bacterial symbiosis has been aware of owning multiple merits of low energy consumption and little greenhouse gas emission. Thus, the responses of microalgal-bacterial symbiosis to emerging pollutants in wastewater treatment have become a hotspot in recent years. In this review paper, the removal performance of microalgal-bacterial symbiosis on organics, nitrogen and phosphorus in wastewater containing emerging pollutants has been summarized. The adaptation mechanisms of microalgal-bacterial symbiosis to emerging pollutants have been analyzed. It is found that antibiotics usually have hormesis effects on microalgal-bacterial symbiosis, and that microalgal-bacterial symbiosis appears to show more capacity to remove tetracycline and sulfamethoxazole, rather than oxytetracycline and enrofloxacin. Generally, microalgal-bacterial symbiosis can adapt to heavy metals at a concentration of less than 1 mg/L, but its capabilities to remove contaminants can be significantly affected at 10 mg/L heavy metals. Further research should focus on the influence of mixed emerging pollutants on microalgal-bacterial symbiosis, and the feasibility of using selected emerging pollutants (e.g., antibiotics) as a carbon source for microalgal-bacterial symbiosis should also be explored. This review is expected to deepen our understandings on emerging pollutants removal from wastewater by microalgal-bacterial symbiosis.

Aqueous Structure of Lanthanide-EDTA Coordination Complexes Determined by a Combined DFT/EXAFS Approach

Sustainable production of rare earth elements (REEs) is critical for technologies needed for climate change mitigation, including wind turbines and electric vehicles. However, separation technologies currently used in REE production have large environmental footprints, necessitating more sustainable strategies. Aqueous, affinity-based separations are examples of such strategies. To make these technologies feasible, it is imperative to connect aqueous ligand structure to ligand selectivity for individual REEs. As a step toward this goal, we analyzed the extended X-ray absorption fine structure (EXAFS) of four lanthanides (La, Ce, Pr, and Nd) complexed by a common REE chelator, ethylenediaminetetraacetic acid (EDTA) to determine the aqueous-phase structure. Reference structures from density functional theory (DFT) were used to help fit the EXAFS spectra. We found that all four Ln-EDTA coordination complexes formed 9-coordinate structures with 6 coordinating atoms from EDTA (4 carboxyl oxygen atoms and 2 nitrogen atoms) and 3 oxygen atoms from water molecules. All EXAFS fits were of high quality (R-factor < 0.02) and showed decreasing average first-shell coordination distance across the series (2.62-2.57 Å from La-Nd), in agreement with DFT (2.65-2.56 Å from La-Nd). The insights determined herein will be useful in the development of ligands for sustainable rare earth elements (REE) separation technologies.

A colloidal gold immunoassay strip assay for cadmium detection in oilfield chemicals

Cadmium ions (Cd2+) are some of the major pollutants in oilfield chemicals. To reduce the pollution of oilfield chemicals, it is necessary to detect and control the content of Cd2+. In this study, we synthesized a highly sensitive and specific monoclonal antibody against Cd2+ with an IC50 of 1.97 ng mL-1 and no cross-reactivity. Based on this antibody, a colloidal gold immunoassay strip detection assay with an IC50 of 1 mg kg-1 and a detection range of 1.0-20 mg kg-1 in oilfield chemicals was developed. This assay could be completed in 20 min and can be used for Cd2+ on-site testing in oilfield chemicals and improve supervision efficiency in oil exploration and development.

Bioinspired "cage traps" for closed-loop lead management of perovskite solar cells under real-world contamination assessment

Despite the remarkable progress made in perovskite solar cells, great concerns regarding potential Pb contamination risk and environmental vulnerability risks associated with perovskite solar cells pose a significant obstacle to their real-world commercialization. In this study, we took inspiration from the ensnaring prey behavior of spiders and chemical components in spider web to strategically implant a multifunctional mesoporous amino-grafted-carbon net into perovskite solar cells, creating a biomimetic cage traps that could effectively mitigate Pb leakage and shield the external invasion under extreme weather conditions. The synergistic Pb capturing mechanism in terms of chemical chelation and physical adsorption is in-depth explored. Additionally, the Pb contamination assessment of end-of-life perovskite solar cells in the real-world ecosystem, including Yellow River water and soil, is proposed. The sustainable closed-loop Pb management process is also successfully established involving four critical steps: Pb precipitation, Pb adsorption, Pb desorption, and Pb recycling. Our findings provide inspiring insights for promoting green and sustainable industrialization of perovskite solar cells.

A Review of Classification, Biosynthesis, Biological Activities and Potential Applications of Flavonoids

Flavonoids represent the main class of plant secondary metabolites and occur in the tissues and organs of various plant species. In plants, flavonoids are involved in many biological processes and in response to various environmental stresses. The consumption of flavonoids has been known to reduce the risk of many chronic diseases due to their antioxidant and free radical scavenging properties. In the present review, we summarize the classification, distribution, biosynthesis pathways, and regulatory mechanisms of flavonoids. Moreover, we investigated their biological activities and discuss their applications in food processing and cosmetics, as well as their pharmaceutical and medical uses. Current trends in flavonoid research are also briefly described, including the mining of new functional genes and metabolites through omics research and the engineering of flavonoids using nanotechnology. This review provides a reference for basic and applied research on flavonoid compounds.

Chemical Bridge-Mediated Heterojunction Electron Transport Layers Enable Efficient and Stable Perovskite Solar Cells

Perovskite solar cells (PSCs) emerged as potential photovoltaic energy-generating devices developing in recent years because of their excellent photovoltaic properties and ease of processing. However, PSCs are still reporting efficiencies much lower than their theoretical limits owing to various losses caused by the charge transport layer and the perovskite. In this regard, herein, an interface engineering strategy using functional molecules and chemical bridges was applied to reduce the loss of the heterojunction electron transport layer. As a functional interface layer, ethylenediaminetetraacetic acid (EDTA) was introduced between PCBM and the ZnO layer, and as a result, EDTA simultaneously formed chemical bonds with PCBM and ZnO to serve as a chemical bridge connecting the two. DFT and chemical analyses revealed that EDTA can act as a chemical bridge between PCBM and ZnO, passivate defect sites, and improve charge transfer. Optoelectrical analysis proved that EDTA chemical bridge-mediated charge transfer (CBM-CT) provides more efficient interfacial charge transport by reducing trap-assisted recombination losses at ETL interfaces, thereby improving device performance. The PSC with EDTA chemical bridge-mediated heterojunction ETL exhibited a high PCE of 21.21%, almost no hysteresis, and excellent stability to both air and light.

Pd@l-asparagine-EDTA-chitosan: a highly effective and reusable bio-based and biodegradable catalyst for the Heck cross-coupling reaction under mild conditions

In this research, a novel supramolecular Pd(ii) catalyst supported on chitosan grafted by l-asparagine and an EDTA linker, named Pd@ASP-EDTA-CS, was prepared for the first time. The structure of the obtained multifunctional Pd@ASP-EDTA-CS nanocomposite was appropriately characterized by various spectroscopic, microscopic, and analytical techniques, including FTIR, EDX, XRD, FESEM, TGA, DRS, and BET. The Pd@ASP-EDTA-CS nanomaterial was successfully employed, as a heterogeneous catalytic system, in the Heck cross-coupling reaction (HCR) to afford various valuable biologically-active cinnamic acid derivatives in good to excellent yields. Different aryl halides containing I, Br and even Cl were used in HCR with various acrylates for the synthesis of corresponding cinnamic acid ester derivatives. The catalyst shows a variety of advantages including high catalytic activity, excellent thermal stability, easy recovery by simple filtration, more than five cycles of reusability with no significant decrease in its efficacy, biodegradability, and excellent results in the HCR using low-loaded Pd on the support. In addition, no leaching of Pd into the reaction medium and the final products was observed.

Water Oxidation by a Copper(II) Complex with 6,6'-Dihydroxy-2,2'-Bipyridine Ligand: Challenges and an Alternative Mechanism

Recently, copper(II) complexes have been extensively investigated as oxygen-evolution reaction (OER) catalysts through a water-oxidation reaction. Herein, new findings regarding OER in the presence of a Cu(II) complex with 6,6'-dihydroxy-2,2'-bipyridine ligand are reported. Using scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, Raman spectroscopy, in situ visible microscopy, in situ visible spectroelectrochemistry, X-ray absorption spectroscopy, and electrochemistry, it is hypothesized that the film formed on the electrode's surface in the presence of this complex causes an appropriated matrix to produce Cu (hydr)oxide. The resulting Cu (hydr)oxide could be a candidate for OER catalysis. The formed film could form Cu (hydr)oxide and stabilize it. Thus, OER activity increases in the presence of this complex.

Fabrication of Naturally Derived Chitosan and Ilmenite Sand-Based TiO2/Fe2O3/Fe-N-Doped Graphitic Carbon Composite for Photocatalytic Degradation of Methylene Blue under Sunlight

Fabrication of chitosan and ilmenite sand-based novel photocatalysts through the catalytic graphitization of chitosan is reported. Nanocomposites consisted of TiO2, Fe2O3 and Fe nanoparticles dispersed on a nitrogen-doped graphitic carbon framework. The surface area, pore volume and macropore structure of the carbon matrix is disturbed by the heterogeneously distributed nanoparticles. The extent of graphitization expanded with increasing metal loading as indicated by variation in the ID/IG ratio. The nanomaterial’s surface consists of Fe3+ and Ti4+, and graphitic, pyridinic and pyrrolic nitrogen were found in the carbon matrix. The band gap values of the composites varied in the 2.06–2.26 eV range. The photocatalytic activity of the synthesized nanomaterials was determined, and the highest rate constant for the photodegradation of methylene blue under sunlight was 4.4 × 10−3 min−1, which resulted with 10 mg/L MB and 25 mg of the best-performing catalyst. The rate constant rose with increasing concentrations of persulfate added to the medium. The rate constant greatly diminished with the addition of isopropyl alcohol as it scavenged hydroxyl radicals. The presence of co-pollutants including Pb2+, rhodamine B, PO43− and Cl− curtailed the rate of reaction. The activity reduced with an increasing number of uses of the catalyst.

Promoted elimination of metronidazole in ferrous ions activated peroxydisulfate process by gallic acid complexation

We applied gallic acid (GA) as the complexing agent to stabilizing the regeneration of Fe²⁺ during the Fe²⁺/peroxydisulfate (PDS) Fenton-like reaction for promoting the removal of metronidazole (MTZ). This research evaluated the elimination of MTZ by optimizing the dose of GA and Fe²⁺ and pH condition. MTZ removal reached 83% at the GA: Fe²⁺ molar ratio of 1:1 (30 μM) and initial pH 5 and 6.2 after 120 min, and the kinetics showed two degradation phases (k_obs1 = 0.09636 for the rapid stage and k_obs2 = 0.01056 for the slow stage). The Fe²⁺ and GA complexes could expand the range of pH applicability and effectively stabilize the regeneration of Fe²⁺, which ultimately promoted the decontamination of MTZ. Sulfate radical (SO₄^.-), hydroxyl radicals, and singlet oxygen were proved to exist in this ternary system and contribute to MTZ removal, and SO₄^.- played the dominant role. Furthermore, the possible pathways and mechanisms for MTZ degradation were proposed, and the simulation result indicated that the toxicity of degradation intermediates of MTZ were declined. The GA assisted Fe²⁺/PDS system provided an improved promising advanced oxidation process for organic wastewater disposal.

Synthesis of functional poly(amidoamine) dendrimer decorated apple residue cellulose for efficient removal of aqueous Hg(II)

Water pollution caused by Hg(II) exerts hazardous effect to the environment and public health. The design and fabrication of eco-friendly bioadsorbents for efficient removal of Hg(II) from aqueous solution is a promising strategy. Herein, a series of bioadsorbents were synthesized by the decoration of apple residue cellulose with different generation (G) Schiff base functionalized poly(amidoamine) (PAMAM) dendrimers (SA-G0/CE, SA-G1.0/CE and SA-G2.0/CE). The structures of SA-G0/CE, SA-G1.0/CE and SA-G2.0/CE were characterized and their adsorption performances were determined comprehensively by considering various factors. The maximum adsorption capacity of SA-G0/CE, SA-G1.0/CE and SA-G2.0/CE for Hg(II) are 1.18, 1.73 and 1.88 mmol·g^-1, respectively. The as-prepared bioadsorbents exhibit competitive adsorption capacity as compared with other reported adsorbents. Moreover, they exhibit remarkable adsorption selectivity toward Hg(II) with the coexistence of Ni(II), Cd(II), Mn(II), or Pb(II). The bioadsorbents display satisfactory adsorption performance in real water sample and can be reused with good regeneration property. Adsorption mechanism reveals that the functional groups of OH, -CONH-, CN and NC take part in the adsorption for Hg(II). The work not only opens a pathway to realize the reuse of apple residue, but also provides a promising strategy to construct efficient bioadsorbents for the decontamination of Hg(II) from aqueous solution.

Revisiting carboxylic group functionalization of silica sol-gel materials

The carboxylic chemical group is a ubiquitous moiety present in amino acids, a ligand for transition metals, a colloidal stabilizer, and a weak acidic ion-exchanger in polymeric resins and given this property, it is attractive for responsive materials or nanopore-based gating applications. As the number of uses increases, subtle requirements are imposed on this molecular group when anchored to various platforms for the functioning of an integrated chemical system. In this context, silica stands as an inert and multipurpose platform that enables the anchoring of multiple chemical entities combined through several orthogonal synthesis methods on the interface. Surface chemical modification relies on the use of organoalkoxysilanes that must meet the demand of tuned chemical properties; this, in turn, urges for innovative approaches for having an improved, but simple, organic toolbox. Starting from commonly available molecular precursors, several approaches have emerged: hydrosilylation, click thiol-ene additions, the use of carbodiimides or the reaction between cyclic anhydrides and anchored amines. In this review, we analyze the importance of the COOH groups in the area of materials science and the commercial availability of COOH-based silanes and present new approaches for obtaining COOH-based organoalkoxide precursors. Undoubtedly, this will attract widespread interest for the ultimate design of highly integrated chemical platforms.

Versatile crosslinking synthesis of an EDTA-modified UiO-66-NH2/cotton fabric composite for simultaneous capture of heavy metals and dyes and efficient degradation of organophosphate

The metal-organic frameworks/cotton fabric composites (MOFs/CFCs) have emerged as a new type of prospective materials for environmental cleanup, due to their convenient recyclability and high removal efficiency towards hazardous pollutants. However, their practical applications are limited by complicated synthetic conditions, insufficient interface bonding and poor adsorption capacity. Herein, for the first time, a robust ethylenediaminetetraacetic acid (EDTA)-functionalized MOFs/CFC is prepared based on UiO-66-NH₂ crystals by using EDTA dianhydride as the cross-linking agent, and applied for simultaneous removal of heavy metals and dyes, as well as degradation of chemical warfare agents. The as-prepared EDTA-UiO-66-NH₂/CFC shows extraordinary monocomponent adsorption performance with maximum adsorption capacity of 158.7, 126.2, 131.5, 117.4 and 104.5 mg/g for Cd(II), Cu(II), methylene blue, crystal violet and safranin O, respectively. Interestingly, in metal-dyes binary system, the uptake of Cu(II) by EDTA-UiO-66-NH₂/CFC increases significantly when co-existing high concentration of dyes. The results indicate that the synergistic and simultaneous removal of both dyes and metal from complex systems can be realized by EDTA-UiO-66-NH₂/CFC via multiple mechanisms. The EDTA-UiO-66-NH₂/CFC also exhibits an outstanding catalytic performance for degrading dimethyl 4-nitrophenylphosphate. Besides, it can be reused for several times without obvious decrease of its adsorption and catalysis efficiencies. More impressively, the cross-linking reaction approach can not only anchor UiO-66-NH₂ crystals firmly onto cotton fabric, but also facilitate in-situ formation of abundant adsorption sties on the adsorbent surface. Therefore, this work offers a simple and versatile synthetic strategy to develop high-performance environmental material for multiple pollutants remediation.

Removal of emerging organic micropollutants via modified-reverse osmosis/nanofiltration membranes: A review

Hazardous micropollutants (MPs) such as pharmaceutically active compounds (PhACs), pesticides and personal care products (PCPs) have emerged as a critical concern nowadays for acquiring clean and safe water resources. In the last few decades, innumerable water treatment methods involving biodegradation, adsorption and advanced oxidation process have been utilized for the removal of MPs. Of these methods, membrane technology has proven to be a promising technique for the removal of MPs due to its sustainability, high efficiency and cost-effectiveness. Herein, the aim of this article is to provide a comprehensive review regarding the MPs rejection mechanisms of reverse osmosis (RO) and nanofiltration (NF) membranes after incorporation of nanomaterials and also surface modification atop the PA layer. Size exclusion, adsorption and electrostatic charge interaction mechanisms play important roles in governing the MP removal rate. In addition, this review also discusses the state-of-the-art research on the surface modification of thin film composite (TFC) membrane and nanomaterials-incorporated thin film nanocomposite (TFN) membrane in enhancing MPs removal performance. It is hoped that this review can provide insights in modifying the physicochemical properties of NF and RO membranes to achieve better performance in water treatment process, particularly for the removal of emerging hazardous substances.

Amidoxime functionalized PVDF-based chelating membranes enable synchronous elimination of heavy metals and organic contaminants from wastewater

Aiming at the synchronous elimination of heavy metals and organic contaminants from wastewater, the amidoxime functionalized PVDF-based chelating membrane was fabricated in this study. The structure and morphology of the chelating membrane were characterized using infrared spectroscopy (FT-IR), nuclear magnetic resonance spectrometer (NMR) and scanning electron microscopy (SEM). The SEM results show that the chemical modification with amidoxime groups did not damage the structure of the PVDF-based membrane. The chelating membrane has a high removal efficiency for Cu²⁺ (77.33%) and Pb²⁺ (79.23%) owing to the chemisorption through coordination bonds. However, the chelating membrane exhibits a low removal efficiency for Cd²⁺ (29.88%) due to the physical adsorption. The chelating membrane has a high rejection efficiency of BSA (95.17%) and lysozyme (70.09%), which is attributed to the sieving effect and increased hydrophobicity. Furthermore, the membrane performance for simultaneously removing metals and proteins from simulated wastewater was examined. The interaction of metal ions with proteins (BSA and lysozyme) can enhance the ion removal efficiency of the chelated membrane, but decrease the protein rejection efficiency due to the destructive effect. The amidoxime functionalized PVDF-based chelating membrane has a high potential for application in wastewater treatment.

Synergistic Effect of Bio-Inspired Nanochannels: Hydrophilic DNA Probes at Inner Wall and Hydrophobic Coating at Outer Surface for Highly Sensitive Detection

During the past few decades, bio-inspired nanochannels have been well developed and applied in biosensing, energy transfer, separation, and so on. Here, inspired by the synergistic effect of biological nanopores, biomimetic solid-state nanochannels with hydrophilic DNA probes at the inner wall (DNA@IW_Hydrophilic ) and hydrophobic coating at the outer surface (None@OS_Hydrophobic ) are designed. To demonstrate their prompted sensing properties, Hg²⁺ and its specific probe are selected as target and hydrophilic DNA probes, respectively. Compared with the traditional solid-state nanochannels with hydrophilic probes distributed on both the inner wall and outer surface, the nanochannels with DNA@IW_Hydrophilic +None@OS_Hydrophobic significantly decrease the limit of detection (LOD) by 10⁵ -fold. The obvious improvement of sensitivity (with LOD of 1 nM) is attributed to the synergistic effect: None@OS_Hydrophobic results in the nanochannel's effective diameter decrease and DNA@IW_Hydrophilic induces a specific sensing target. Meanwhile, nanomolar detection of Hg²⁺ in human serum and in vivo fish muscle are achieved. Through molecular dynamics simulation, the synergistic effect can be confirmed by ion fluxes increasement; the relative carbon nanotube increases from 135.64% to 135.84%. This work improves the understanding of nanochannels' synergistic effect and provides a significant insight for nanochannels with improved sensitivity.

l-Asparagine-EDTA-amide silica-coated MNPs: a highly efficient and nano-ordered multifunctional core-shell organocatalyst for green synthesis of 3,4-dihydropyrimidin-2(1H)-one compounds

In this study, new l-asparagine grafted on 3-aminopropyl-modified Fe3O4@SiO2 core-shell magnetic nanoparticles using the EDTA linker (Fe3O4@SiO2-APTS-EDTA-asparagine) was prepared and its structures properly confirmed using different spectroscopic, microscopic and magnetic methods or techniques including FT-IR, EDX, XRD, FESEM, TEM, TGA and VSM. The Fe3O4@SiO2-APTS-EDTA-asparagine core-shell nanomaterial was found, as a highly efficient multifunctional and recoverable organocatalyst, to promote the efficient synthesis of a wide range of biologically-active 3,4-dihydropyrimidin-2(1H)-one derivatives under solvent-free conditions. It was proved that Fe3O4@SiO2-APTS-EDTA-asparagine MNPs, as a catalyst having excellent thermal and magnetic stability, specific morphology and acidic sites with appropriate geometry, can activate the Biginelli reaction components. Moreover, the environmental-friendliness and nontoxic nature of the catalyst, cost effectiveness, low catalyst loading, easy separation of the catalyst from the reaction mixture and short reaction time are some of the remarkable advantages of this green protocol.