Toxic Heavy Metal Ions Research Articles

Cloud point extraction of heavy metal ions for wastewater remediation: an equilibrium and kinetic study

Abstract Surfactants offer a promising alternative for the efficient and environmentally friendly removal of organic pollutants and toxic heavy metal ions from various media. Their high efficiency and environmental compatibility make them a valuable option for remediation efforts. This study focuses on the cloud point extraction (CPE) of ions from aqueous solutions using biodegradable nonionic surfactants combined with ionic surfactants instead of chelating agents. Phase diagrams of binary surfactant/water systems were first constructed. The effects of salt, inorganic contaminants, and ionic surfactants on the cloud point (Tc) were then investigated. At temperatures above the cloud point, two distinct phenomena were observed and monitored over time: phase separation and phase clarification. The kinetic process was studied using the Turbiscan Lab Expert. Extraction results were evaluated based on four responses: extraction yield (E%), residual concentrations of solute (Xs,w) and surfactant (Xt,w) in the dilute phase, and volume fraction of coacervate at equilibrium (Φ C). Empirical modelling gives a satisfactory agreement between experimental and calculated values. The capacity of CPE to simultaneously remove an organic pollutant and a toxic heavy metal was demonstrated.

A Review on Pyridine Based Colorimetric and Fluorometric Chemosensor for Detection of Hg2+ ion.

Pyridine, N-containing heterocyclic organic compound, displays strong coordination capabilities with various metal ions. It can be synthesized through various methods, such as Friedlander synthesis, heterocumulene synthesis, cross-coupling reactions, the Radziszewski reaction, Bonnemann cyclization, as well as cobalt-catalyzed synthesis. Experimental and spectroscopic analyses have demonstrated a strong binding affinity between pyridine and several heavy metal ions, including Pb2+, Hg2+, and Cd2+ ions. The escalating environmental pollution caused by the disposal of heavy metal ions in rivers, open air, and water reservoirs poses a significant threat to both ecosystem and human health. To address these environmental challenges, a cost-effective and easily synthesized chemosensor has been prepared for identifying toxic heavy metal ions in various samples. Pyridine's photophysical properties make it an effective sensor for detecting Hg2+ ions, displaying fluorescence quenching or enhancement in their presence. The coordination between pyridine and Hg2+ ions lead to shifts in the absorption spectra. The pyridine-based sensor has been evaluated for its sensitivity, selectivity, and detection limits under different experimental conditions. Pyridine's solubility and environmental stability make it applicable for real-time detection, making pyridine probes valuable tool for monitoring toxic Hg2+ ions in the environment. The results demonstrate that the pyridine-based chemosensor exhibits good selectivity and sensitivity for targeting Hg2+ ions, with detection limits within acceptable ranges. This review (from years 2011 to 2023) emphasizes the preparation of various substituted pyridine compounds as selective, sensitive, and specific sensors for real-time detection of Hg2+ ions.

Real-Time Wireless Detection of Heavy Metal Ions Using a Self-Powered Triboelectric Nanosensor Integrated with an Autonomous Thermoelectric Generator-Powered Robotic System.

The integration of the Internet of Things (IoT) with advanced sensing technologies is transforming environmental monitoring and public health protection. In this study, a fully self-powered and automated chemical sensing system is developed and integrated with a robotic hand for "touch and sense" detection of toxic heavy metal ions (Pb2⁺, Cr⁶⁺, As3⁺) in aquatic environments. The system combines a self-powered solid-liquid triboelectric nanosensor (SL-TENS) with a thermoelectric generator (TEG), which harnesses ambient heat to power the robotic hand, eliminating the need for external power sources. The robotic hand is controlled wirelessly via an exo-hand, minimizing the risk of exposure during remote monitoring. The sensing component uses copper oxide nanowires (CuO NWs) coated with ion-selective membranes (ISMs) to enhance triboelectric output and enable highly selective ion detection. The system demonstrates effective real-time, on-site detection in lake water and data transmitted wirelessly to the user. This innovative approach provides a highly safe and efficient method for detecting hazardous pollutants in difficult-to-access areas, offering significant potential for wireless and real-time environmental monitoring and hazard prevention, thus contributing to the safeguarding of human health. This study presents a novel advancement in the field of IoT-enabled environmental monitoring systems.

Study on the new slow-release carbon source biochemistry and its improvement of SRB on the acid mine drainage treatment

The content of sulfate and heavy metals in acidic mine drainage (AMD) exceeds the standard severely, and the acidity is extremely high, causing serious harm to the environment. SRB can efficiently remove sulfates through its own metabolism. The treatment of AMD by SRB faces problems such as carbon source scarcity and heavy metal ion toxicity to SRB. In this study, corn cob and polycaprolactone were embedded to prepare a novel slow-release carbon source (PSCL), which simultaneously achieves carbon source supply and metal ion removal. Through adsorption isotherms, kinetics, thermodynamics studies, and various characterization analyses, it is known that PSCL removes Cu2+ and Zn2+ through ion exchange, physical and chemical adsorption, electrostatic attraction, and surface complexation. PSCL carbon release experiments and characterization results confirm that its surface carbon distribution is dense, the molecular weight of DOM in the leachate is small, the degree of humification is low, and it has a porous structure, making it a good carbon release material and biological attachment. The experimental results of PSCL enhanced SRB treatment of AMD showed that the removal rates of SO42−, Cu2+ and Zn2+ could be increased to 97.48%, 98.11% and 90.42%, respectively, with a effluent pH of 7.05, effectively improving the water quality of AMD. This study provides new materials and methods to address the limitations of SRB in treating actual AMD.

Synthesis and structure of an aqueous stable Cu(II)-based coordination polymer with multifunctional fluorescence sensing property

Advanced methods for both biological and environmental hazardous pollutants are of sustained interest. Herein, a new coordination polymer, namely, [Cu2(OH)(1,2,4-bca)(bmoe)]·H2O (Cu-CP) has been hydrothermally constructed with a mix-ligand strategy, employing 1,2,4-benzenetricarboxylic acid (1,2,4-bca) and 1,1′-bis(1H-benzimidazolyl) oxydiethane (bmoe) as organic ligands. The intrinsic strong blue-light emission and the great stability in water solutions with the broad range of pH values (pH = 4 − 12) of Cu-CP provide a platform for practical fluorescence sensing application in water samples. Fluorescence measurements reveal that Cu-CP displays interesting multi-responsive dection activities toward toxic heavy-metal ions Cr2O72- / CrO42− / MnO4−, nitrofuran antibiotics nitrofurantoin (NFT) / nitrofurazone (NFZ) and acetylacetone (ACAC) in aqueous solutions achieving both high sensitivity and low detection limits (micromolar for Cr(VI) / Mn(VII) / ACAC and nanomolar for NFT / NFZ). Furthermore, the interference experiments have verified its excellent selectivity. A synergetic contribution of internal filtration effect (IFE) and Förster resonance energy transfer (FRET) between Cr2O72- / CrO42− / MnO4− and the framework of Cu-CP realize the fluorescence quenching behavior for Cr(VI) / Mn(VII) detection, while FRET, IFE and photoinduced electron transfer (PET) mechanisms are synergistically responsible in the case of NFT / NFZ, ACAC sensing supported by the molecular simulations and UV−vis spectral overlap experiments. This present work affords precious guidance for the effective and facile design and preparation of multifunctional luminescent coordination polymers with promising performance.

A novel trimesoyl chloride/hyper branched polyethyleneimine/MOF (MIL-303)/P84 co-polyimide nanocomposite mixed matrix membranes with an ultra-thin surface cross linking layer for removing toxic heavy metal ions from wastewater

In this study, a positively charged nanofiltration (NF) nanocomposite mixed matrix membrane (MMM) was developed by incorporating metal-organic frameworks (MOFs) (MIL-303) into P84 co-polyimide and cross-linking with hyperbranched polyethyleneimine (HPEI). A very thin selective layer was subsequently formed on the cross-linked membrane surface using trimesoyl chloride (TMC). The incorporation of MIL-303 introduced specific water channels, enhancing the permeance of the nanocomposite MMMs. Additionally, it improved hydrophilicity and influenced the diffusion of the TMC monomer through the channels. The cross-linker HPEI resulted in NF membranes with increased electro-positivity and a reduced mean pore diameter. The very thin crosslinked TMC layer further improved permeance and heavy metal ions rejection of the membrane. This optimized membrane exhibited excellent rejection for both bivalent and monovalent ions, as well as heavy metal ions, effectively overcoming the common trade-off between permeance and rejection in NF membranes. The membrane demonstrated a remarkable permeance of 13.0 LMH/bar, coupled with exceptional rejection for heavy metal ions (96.8 % for Zn²⁺, 95.2 % for Ni²⁺, 95.7 % for Cu²⁺, 93.2 % for Pb²⁺, and 92.9 % for Cd²⁺). The TMC/HPEI/MIL-303/P84 system presented in this study holds significant promise for customizing high-performance positively charged NF membranes for the removal of heavy metal ions from wastewater.

Enhanced peroxidase-like activity based on electron transfer between platinum nanoparticles and Ti3C2TX MXene nanoribbons coupled smartphone-assisted hydrogel platform for detecting mercury ions

BackgroundHeavy metal pollution poses a serious threat to the ecological environment. Mercury ion (Hg2+) is a class of highly toxic heavy metal ions, which is bioaccumulative, difficult to breakdown, and has a significant affinity with sulfur and thiol-containing proteins, which seriously affects environmental safety and human health. Nanozyme-based sensing methods are expected to be used to detect toxic heavy metal ions. However, the application of precious metal nanozymes to develop portable sensors with simplicity, high stability, and high sensitivity has not been explored to a large extent. ResultsIn this paper, based on MXene's unique adsorption capacity for certain precious metal ions, PtNPs/Ti3C2TXNR composites were successfully prepared by in-situ growth of Pt nanoparticles (PtNPs) on the surface of Ti3C2TX MXene nanoribbons (Ti3C2TXNR) using the hydrothermal technique. Experimental data revealed PtNPs/Ti3C2TXNR exhibited superior peroxidase-like activity, attributed to the synergistic effect of well-dispersed ultrasmall PtNPs and electron transfer effect. Hg2+ can significantly inhibit enzyme-like activity of PtNPs/Ti3C2TXNR due to specific capture and partial in-situ reduction of PtNPs, so a colorimetric sensor was constructed for ultra-trace detection of Hg2+ with a linear range of 0.2 nM and 400 nM. Furthermore, using the portable detecting capabilities of smartphones and hydrogel, a smartphone-assisted hydrogel sensing platform of Hg2+ was constructed. Notably, the two-mode sensing platforms exhibited outstanding detection performance with LOD values as low as 15 pM (colorimetric) and 26 pM (hydrogel), respectively, superior to recently reported nanozyme-based Hg2+ sensors. SignificanceCompared with other methods, the PtNPs/Ti3C2TXNR-based dual-mode sensor designed in this paper has superior sensitivity, high selectivity, simple operation and portability. In particular, the dual-output sensing strategy enables self-confirmation of detection results, greatly improving the reliability of the sensor, and is expected to be used for the on-site determination of trace mercury ions.

Micro-droplet printed ion-selective membrane sensors for in situ monitoring of marine heavy metal ions

Fast, accurate, and reliable techniques for marine toxic heavy metal ions (HMI) detection are critical for the ecological environment and human health. One of the fatal drawbacks of traditional ion selective electrochemical sensors is that the modification of electrode cannot be accurately quantified, resulting in poor repeatability of the detection electrode and large error between the multi-electrode detection results. In order to tackle this challenge, this study presents ultra-fine micro-droplet printed electrodes for the in-situ detection of Cd2+, a carcinogenic and toxic HMI commonly found in the ocean. The ion selective membrane casting liquid was dispersed into tiny droplets with a diameter of micron through microfluidic technology, and the microdroplets were precisely arranged on the electrode surface. As a result, the modification error of electrode was reduced to pL level (accurate to 10 pL), which greatly improved the repeatability between electrodes prepared in different batches. The results of experiments with pure electrolyte, interference ions and artificial seawater indicated that the micro-droplet printed sensors possessed excellent properties of accuracy, precision, repeatability, and anti-interference. This novel micro-droplet printed sensor has the potential to capture an accurate picture of nearshore HMI in heterogeneous environments under shock conditions.

Utilization of Base and Acid Modified Rice Husk-Corncobs Composite for Removal of Chromium (VI) Ion in Simulated Tannery Wastewater

In the ever-increasing blind race of industrialization and urbanization environmental contamination by toxic heavy metal ions is becoming a serious issue for both scientists and masses. Hence, the objective of this paper was to evaluate the utilization of base (BMOD) and acid (AMOD) modified rice husk-corncobs composite for the removal of chromium (VI) Ion in simulated tannery wastewater using appropriate standard techniques. SEM-EDX, XRD and FTIR characterizations revealed the elemental composition, crystallographic structures and the chemical bonds respectively. The results of the sorption kinetic study showed that the data fitted well with the pseudo-second order model for both acid modified (AMOD) and base modified (BMOD) biosorbent with a maximum adsorption of 28.46 mg/g and 39.66 mg/g respectively. The results of the sorption isotherm study showed that they both fitted Freundlich isotherm model. From the results obtained, rice husk and corn cob were effective biosorbent for the removal of Cr (VI) ion from tannery effluent.

Nucleic acid-functionalized upconversion luminescence biosensor based on strand displacement-mediated signal amplification for the detection of trivalent chromium ions

BackgroundRapid industrial development has generated serious pollution, including the presence of toxic and harmful heavy metal ions. Among them, trivalent chromium ion (Cr3+) is a very important element that poses a threat to life and health in our industrial wastewater pollution. Thus, it is important to develop efficient fluorescence methods for Cr3+ detection. In this study, an upconversion luminescence biosensor for detecting Cr3+ was constructed based on a DNAzyme, strand displacement reaction (SDR), and DNA-functionalized upconversion nanoparticles (UCNPs). ResultsThe sulfonate-rich poly (sodium 4-styrene sulfonate) (PSS) was modified onto the surface of UCNPs, forming UCNPs@PSS. Then, NH2-Capture probe DNA (NH2-Cp) was further modified onto the UCNPs@PSS surface through sulfonylation, resulting in UCNPs@PSS@NH2-Cp. The DNAzyme activated by Cr3+ triggered the release of the primer probe (Pp), which initiated the SDR system cycle, thereby releasing a tetramethylrhodamine (TAMRA)-modified signal probe (TAMRA-Sp). Finally, UCNPs@PSS@NH2-Cp bound to TAMRA-Sp through complementary base pairing, causing UCNPs and TAMRA to approach each other. Because of the luminescence resonance energy transfer (LRET) mechanism, the upconversion luminescence (UCL) signal of the UCNPs was quenched by TAMRA, enabling the detection of Cr3+ by the change of I585/I545 ratio. This biosensor has good stability, selectivity, and sensitivity, with a linear range of 0.5–75 nM and a detection limit of 0.135 nM for Cr3+. Significance and noveltyFirstly, based on LRET between UCNPs and TAMRA, the quantitative analysis of Cr3+ is achieved through the changes of ratio fluorescence. Secondly, the specificity of the biosensor is improved by utilizing the specific recognition of DNA enzymes. Thirdly, the signal amplification technology of the SDR cycle greatly improves the sensitivity of biosensor. This biosensor will be useful for future environmental safety monitoring and biopsy of biological fluids.

A novel 3D hierarchical NiFe-LDH/graphitic porous carbon composite as multifunctional adsorbent for efficient removal of cationic/anionic dyes and heavy metal ions

Developing effective adsorbents for wastewater purification is crucial, as excessive emissions of toxic dyes and heavy metal ions have been proven harmful to ecosystems and human health. A NiFe-layered double hydroxide/graphitic porous carbon (NiFe-LDH/GPC) composite was fabricated by introducing NiFe-LDH nanosheets into GPC via a simple hydrothermal method to utilize the advantages of both materials fully, and thus ultimately obtain a composite adsorbent with improved adsorption properties. The samples obtained were comprehensively characterized by various characterization means, and the effects of several critical influential factors on the pollutant uptake capability of the NiFe-LDH/GPC were also studied through batch experiments. The results show that the as-synthesized NiFe-LDH/GPC exhibits a three-dimensional (3D) fluffy ultrathin-wall hierarchical porous structure, which possesses a high specific surface area and pore volume separately up to 506.74 m2/g and 0.22 cm3 g−1 as well as a relatively narrow pore size distribution. These characteristics bring advantages to enhance the adsorption ability of the NiFe-LDH/GPC for cationic/anionic dyes and heavy metal ions such as congo red (CR), malachite green (MG) and hexavalent chrome (Cr(VI), which reached the maximum adsorption capacity of 1726.51 mg/g, 1157.11 mg/g and 155.72 mg/g under the optimum conditions, respectively. Meanwhile, the adsorption behavior can be well described by the pseudo-second-order kinetic model and Langmuir isotherm model, reflecting that the sorption process mainly occurred chemically in the adsorbent monolayer. Furthermore, the NiFe-LDH/GPC maintained relatively high adsorption performance after multicycle testing, manifesting its good recyclability and stability.

Gold nanoparticle-enhanced D-shaped optical fiber sensor for mercury ion detection.

Mercury ions (Hg2+) are highly toxic heavy metal ions that pose serious health risks to humans when present at concentrations above the safety threshold. Therefore, the development of a rapid and effective Hg2+ detection method is of significant importance. In this study, based on surface plasmon resonance (SPR) technology integrated with COMSOL simulation analysis, a highly sensitive and selective Hg2+ sensing system is constructed. Initially, gold nanoparticles and the surface of a fiber-optic gold film are modified by sodium sulfide (Na2S). In the presence of Hg2+, the sulfur ions on the modified gold film and gold nanoparticles specifically bind to Hg2+, forming the composite structure Au/S-Hg2+-S/AuNPS. Due to the strong electromagnetic coupling between the gold nanoparticles and the gold film, a significant SPR wavelength shift occurs. These results show that the Hg2+ sensor has high sensitivity and enhanced selectivity. The detection limit for mercury ions was 8.15 nM, and the recovery rate in real environmental samples was up to 90.1-97.3%. This sensing system provides an alternative method for rapid and accurate determination of mercury content.

Chromium adsorption efficiency by functional polymeric nanocomposite membrane: A case study for environmental sustainability

AbstractWe have designed and developed nonwoven fabric supported electrospun polymeric nanofibrous‐based membrane for robust filtration system for ecological sustainability of clean water. The fabricated nanocomposites filters were tested for the removal of chromium (VI) toxic heavy metal ions from contaminated feedstock water. The interpenetrating network like morphological structure obtained from pure and composite nanofibers‐based membranes have been thoroughly investigated to understand the structure–properties of highly entangled system. It has been found that incorporating functional moieties onto nanocomposite membranes significantly impacts the absorption efficiency of toxic metals. The pore sizes of the hierarchical geometries have been varied to insight into its impact on flow rate and efficiency of filtration. The strategy of interfacing the multifunctional composite polyethylene terephthalate nanofiber membrane supported on nonwoven fabric to generate heterostructures has found to provide mechanically stable platform for efficient metal ion removal. It has been found by BET surface area analysis that the nanofibers reinforced with functional nanomaterials has controlled pore geometry compared to pristine PET electrospun nanofibers which lead to higher absorption of metal ions. We have highlighted the importance of mechanically stable electrospun polymeric nanofibers membrane‐based mitigation strategies to meet the huge demand of potable water for long‐term environmental sustainability.Highlights Mechanically toughened freestanding nanofibers mat supported on nonwoven fabric. Functionally upgrade nanofibers by incorporation of carbon based nanofillers. Controlled porosity by morphological optimization for removal of contaminates.

Bioremediation strategies and mechanisms of bacteria for resistance against heavy metals: a review

Industrial activities often generate by-products that are difficult to degrade, harmful to the environment and, toxic to most of the life forms on earth. Heavy metals are toxic elements that usually present in industrial effluents whose effective management in an eco-friendly manner is important. The treatment of metal-contaminated water through the conventional method of precipitation, ion exchange, electrochemical and reverse osmosis is costly and also likely to generate secondary pollutants. In this review study, we focus on the advantage of bacterial bioremediation to deal with metal toxicity. Bacterial bioremediation offers an eco-friendly and cost-effective alternative for treatment of metal contaminated industrial effluent. Bacteria are considered one of the important microbial systems to be employed for bioremediation purposes. Bacteria utilize the mechanisms of biosorption and bioaccumulation which involve ATP-dependent substrate specific sequestration to remediate the contaminants through redox reactions and enzyme-transformation methods. Bacterial cell wall offers potential chemisorption sites for binding and transportation of metal ion to the bacterial cytoplasm. The potential of bacterial bioremediation can be improved by adopting strategies, providing favorable environment, and using stress adapted strains consisting high metabolic activity, metal selectivity, membrane transport system, efficient biocatalytic and chaperone production ability. The bioremediation efficiency of bacteria is expected to improve many folds through the techniques of genetic modifications involving mutation, plasmid exchange and transposons etc. This study may throw light on the detailed mechanism and strategies adapted by bacteria for the bioremediation of toxic heavy metal ions and open a new way to handle metal toxicity efficiently.

Non-Faradaic Impedimetric Detection of Heavy Metal Ions via a Hybrid Nanoparticle-DNAzyme Biosensor.

Due to rapid industrialization, novel water-quality monitoring techniques for the detection of highly toxic and hazardous heavy metal ions are essential. Herein, a hybrid noble nanoparticle/DNAzyme electrochemical biosensor is proposed for the simultaneous and label-free detection of Pb2+ and Cr3+ in aqueous solutions. The sensor is based on the combination of a two-dimensional naked-platinum nanoparticle film and DNAzymes, whose double-helix configuration disassembles into smaller fragments in the presence of target-specific heavy metal ions. The electrochemical behavior of the fabricated sensor was investigated with non-faradaic electrochemical impedance spectroscopy (EIS), resulting in the successful detection of Pb2+ and Cr3+ well below their maximum permitted levels in tap water. So far, there has been no report on the successful detection of heavy metal ions utilizing the non-faradaic electrochemical impedance spectroscopy technique based on advanced nanomaterials paired with DNAzymes. This is also one of the few reports on the successful detection of chromium (III) via a sensor incorporating DNAzymes.

Thiol-Functionalized Adsorbents through Atomic Layer Deposition and Vapor-Phase Silanization for Heavy Metal Ion Removal.

The removal of toxic heavy metal ions from water resources is crucial for environmental protection and public health. In this study, we address this challenge by developing a surface functionalization technique for the selective adsorption of these contaminants. Our approach involves atomic layer deposition (ALD) followed by vapor-phase silanization of porous substrates. We utilized porous silica gel powder (∼100 μm particles, 89 m2/g surface area, ∼30 nm pores) as an initial substrate. This powder was first coated with ∼0.5 nm ALD Al2O3, followed by vapor-phase grafting of a thiol-functional silane. The modified powder, particularly in acidic conditions (pH = 4), showed high selectivity in adsorbing Cd(II), As(V), Pb(II), Hg(II), and Cu(II) heavy metal ions in mixed ion solutions over common benign ions (e.g., Na, K, Ca, and Mg). Langmuir adsorption isotherms and breakthrough adsorption studies were conducted to assess heavy metal binding affinity and revealed the order of Cd(II) < Pb(II) < Cu(II) < As(V) < Hg(II), with a significantly higher affinity for As(V) and Hg(II) ions. Time-dependent uptake studies demonstrated rapid removal of heavy metal ions from aqueous environments, with Hg(II) exhibiting the fastest adsorption kinetics on thiol-modified surfaces. These findings highlight the potential of ALD and vapor-phase silanization to create effective adsorbents for the targeted removal of hazardous contaminants from water.

Advancements in Starch‐Based Aerogels and Hydrogels for Treatment of Water Containing Heavy Metals – A Short Review

AbstractRapid industrialization and profligate use of resources in the present era has led to increase in the concentration of toxic heavy metal ions in water bodies and has become a serious environmental concern. Starch hydrogels and aerogels with engineered functionality, porosity, regeneration characteristics, and high surface to volume ratio have rendered them potential candidates for the adsorption of heavy metal ions from wastewater streams. However, grafting, crosslinking, and composting of the starch aerogels and hydrogels to tailor them in response to various stimuli such as ionic strength, pH, and temperature has added an advantage in the treatment of wastewater containing heavy metal ions. This review critically analyses the various synthesis routes for the production of starch‐based aerogels and hydrogels with physico‐chemical characteristics (amylose content, gelatinization temperature, surface area, density, and porosity) and their applicability to adsorb heavy metal (Cd, Cu, Co, Ni, Cr, Pb, Zn, Fe, and Co) ions from wastewater. Future prospects in the development of economical and robust starch‐based aerogels and hydrogels in terms of their stability and reusability have also been discussed.

Novel High-Performance Functionalized and Grafted Bio-Based Chitosan Adsorbents for the Efficient and Selective Removal of Toxic Heavy Metals from Contaminated Water.

Novel functionalized and/or grafted crosslinked chitosan adsorbents were synthesized and used to remove several toxic heavy metal ions such as nickel, lead, chromium, and cadmium ions from contaminated water. The chitosan biopolymer was functionalized by maleic anhydride (CS_MA) acting also as a crosslinking agent. Glutaraldehyde-crosslinked chitosan (CS_GA) grafted with poly(methyl methacrylate) (CS_MMA) was also synthesized. The synthesized adsorbents were characterized using a variety of analytical techniques such as SEM, TGA, and FTIR, which confirmed their chemical structures and morphology. The adsorption capacity of the adsorbents was analyzed under various conditions of contact time, adsorbent dose, initial concertation, temperature, and pH and evaluated against those of pure chitosan (CS) and the crosslinked chitosan(CS_GA). The ultimate removal conditions were 0.5 g/100 mL adsorbent dose, an initial metal ion concentration of 50 ppm, a temperature of 45 °C, and pH 9. CS_MMA had the highest removal percentages for all metal ions, ranging from 92% to 94%. The adsorption was demonstrated to fit a pseudo-first-order model that followed a Langmuir adsorption isotherm. The results highlight the capacity of the synthesized polymers to efficiently remove major toxic contaminants at low cost from contaminated water, present especially in low-income areas, without harming the environment.

Synergistic Hydrogen Peroxide‐Driven Cation Valence Regulation and La/O Co‐Doped SnS‐Based Oxysulfide Catalyst for Efficient Catalytic Reduction of Toxic Organics and Cr(VI) Under Dark

AbstractA novel La/O co‐doped SnS oxysulfide catalyst (labeled SnLaOS) with heterovalent tin states and sulfur vacancy defects is successfully synthesized for effective catalytic reduction of toxic organics heavy metal ions with NaBH4 in the dark. La/O co‐doped and hydrogen peroxide‐driven SnLaOS catalyst with suitable heterovalent Sn2+/Sn4+ states and sulfur vacancy defects exhibited excellent catalytic reduction capability. The 100 mL 20 ppm of 4‐nitrophenol (4‐NP) and 50 ppm of rhodamine‐B (RhB), methylene blue (MB), methyl orange (MO), and Cr(VI) solution are entirely reduced by 5 mg SnLaOS‐3 within 10, 12, 12, 16, and 14 min, respectively, with durable stability. Synergistic transition metal La3+‐cation and O2−‐anion co‐doped SnS adjusted the energy bandgap and introduced sulfur vacancy defects, and the hydrogen peroxide‐driven regulated the SnLaOS with suitable Sn4+/Sn2+ states ratio. The sulfur vacancies in SnLaOS provide active sites for adsorbed proton for pollutants reduction, and heterovalent Sn2+/Sn4+ states in SnLaOS facilitates electrons efficient transfer through electron hopping between Sn2+ and Sn4+ for pollutants reduction. This study provides a novel efficient catalyst for the water pollutants treatment.

Determination of GaN nanosensor for scavenging of toxic heavy metal ions (Mn2+, Zn2+, Ag+, Au3+, Al3+, Sn2+) from water: Application of green sustainable materials by molecular modeling approach

Gallium nitride nanocage (GaN_NC) can select toxic heavy metals from water. Therefore, it has been found a selective competition for metal cations in the GaN_NC. The electromagnetic and thermodynamic attributes of heavy metals cations-trapped gallium nitride nanocage (GaN_NC) was depicted by material modeling. The data display that heavy metals cations-trapped in the GaN_NC system are resistant materials, with the firm adsorption zone in the center of the cage. Furthermore, charge transfer from GaN_NC to the heavy metals cations demonstrates clear n-type adsorbing manner. The encapsulation of heavy metals cations occurs via chemisorption. In this article, the behavior of trapping of heavy metal ions of Mn2+, Zn2+, Ag+, Au3+, Al3+ and Sn2+ by gallium nitride nanocone for sensing the water metal cations was observed. The nature of covalent features for these complexes has represented the analogous energy amount and vision of the PDOS for the p states of N and d states of heavy metal cations of Mn2+, Zn2+, Ag+, Au3+, Al3+ and Sn2+ through water treatment. The partial density of states (PDOS) can also evaluate an appointed charge group between Mn2+, Zn2+, Ag+, Au3+, Al3+, Sn2+ and GaN_NC which indicate the most stable complex of metallic visage and a certain degree of covalent specifications between heavy metals cations and gallium nitride nanocage. Furthermore, the NMR analysis indicated the notable peaks surrounding metal elements of Mn2+, Zn2+, Ag+, Au3+, Al3+ and Sn2+ through the trapping in the GaN_NC during ion detection and removal from water; however, it can be seen some fluctuations in the chemical shielding treatment of isotropic and anisotropy tensors. Based on the results in this research, the selectivity of metal ion adsorption by gallium nitride nanocage (ion sensor) has been approved as: Ag+ ˃ Au3+ ˃ Mn2+ ≫ Zn2+ ˃ Sn2+ ˃ Al3+. Using quantum theory of atoms in molecules (QTAIMs) method, intermolecular interactions and corresponding parameters at critical bonding points were also investigated.