Decoration of dandelion-like manganese-doped iron oxide microflowers on plasma-treated biochar for alleviation of heavy metal pollution in water

Carbon-based biowaste incorporated with inorganic oxides as a composite is an enticing option to mitigate heavy metal pollution in water resources due to its more economical and efficient performance. With this in mind, we constructed manganese-doped iron oxide microflowers resembling the dandelion-like structure on the surface of cold plasma-treated carbonized rice husk (MnFe2O3/PCRH). The prepared composite exhibited 45% and 19% higher removal rates for Cu2+ and Cd2+, respectively than the pristine CRH. The MnFe2O3/PCRH composite was characterized using XRD, FTIR, FESEM, EDX, HR-TEM, XPS, BET, TGA, and zeta potential, while the adsorption capacities were investigated as a function of pH, time, and initial concentration in batch trials. As for the kinetics, the pseudo-second-order was the rate-limiting over the pseudo-first-order and Elovich model, demonstrating that the chemisorption process governed the adsorption of Cu2+ and Cd2+. Additionally, the maximum adsorption capacities of the MnFe2O3/PCRH were found to be 122.8 and 102.5 mg/g for Cu2+ and Cd2+, respectively. Based on thorough examinations by FESEM-EDS, FTIR, and XPS, the possible mechanisms for the adsorption can be ascribed to surface complexation by oxygen-containing groups, a dissolution-precipitation of the ions with -OH groups, electrostatic attraction between metal ions and the adsorbent's partially charged surface, coordination of Cu2+ and Cd2+ with π electrons by aromatic/graphitic carbon in the MnFe2O3/PCRH, and pore filling and diffusion. Lastly, the adsorption efficiencies were maintained at about 70% of its initial adsorption even after five adsorption-desorption cycles, displaying its remarkable stability and reusability.

Nanomaterials for sustainable remediation: efficient removal of Rhodamine B and lead using greenly synthesized novel mesoporous ZnO@CTAB nanocomposite

This study explores the dual applications of a greenly synthesized ZnO@CTAB nanocomposite for the efficient remediation of Rhodamine B (RhB) and lead (Pb). The synthesis method involves a sustainable approach, emphasizing environmentally friendly practices. FT-IR, XRD, FESEM, zeta potential, and particle size analyzer (PSA), BET, and UV-VIS were used to physically characterize the zinc oxide and CTAB nanocomposite (ZnO@CTAB). The size and crystalline index of ZnO@CTAB are 77.941 nm and 63.56% respectively. The Zeta potential of ZnO@CTAB is about - 22.4 mV. The pore diameter of the ZnO@CTAB was 3.216 nm, and its total surface area was 97.42 m2/g. The mechanism of adsorption was investigated through pHZPC measurements. The nanocomposite's adsorption performance was systematically investigated through batch adsorption experiments. At pH 2, adsorbent dose of 0.025 g, and temperature 50 °C, ZnO@CTAB removed the most RhB, while at pH 6, adsorbent dose of 0.11 g, and temperature 60 °C, ZnO@CTAB removed the most Pb. With an adsorption efficiency of 214.59 mg/g and 128.86 mg/g for RhB and Pb, the Langmuir isotherm model outperforms the Freundlich isotherm model in terms of adsorption. The pseudo-2nd-order model with an R2 of 0.99 for both RhB and Pb offers a more convincing explanation of adsorption than the pseudo-1st-order model. The results demonstrated rapid adsorption kinetics and high adsorption capacities for RhB and Pb. Furthermore, there was minimal deterioration and a high reusability of ZnO@CTAB till 4 cycles were observed.

Green synthesized Cu-doped CeO2nanoparticles for Congo red dye adsorption and antibacterial action

The removal of pollutants from water bodies is crucial for the well-being of humanity and is a topic of global research. Researchers have turned their attention to green synthesized nanoparticles for wastewater treatment due to their eco-friendly nature, biocompatibility, and cost-effectiveness. This work demonstrates the efficient removal of organic dye and both gram-positive and gram-negative bacteria from water bodies using copper-doped cerium oxide nanoparticles synthesized withMurraya Koenigiiextract. Characterized via various methods, the 15% copper doped cerium oxide nanoparticles (Cu 15% NPs) exhibited maximum Congo red dye adsorption (98% degradation in 35 min). Kinetic analysis favoured a pseudo-second-order model, indicating the chemical nature of adsorption. Equilibrium adsorption isotherms aligned with the Langmuir model, indicating homogenous monolayer dye adsorption on the doped adsorbent. The maximum uptake of adsorbate,Qmobtained from Langmuir model for Cu 15% NPs was 193 mg g-1. The study also showed enhanced antibacterial activity againstBacillus subtilis, Staphylococcus aureus, Escherichia coliandPseudomonas aeruginosafor Cu-doped ceria, attributed to generation of reactive oxygen species (ROS) induced by the redox cycling between Ce3+and Ce4+. This substantiated that the green synthesized copper doped cerium oxide nanoparticles are potential candidates for adsorptive removal of Congo red dye and as antibacterial agents.

Removal of chromium(III) from contaminated waters using cobalt ferrite: how safe is remediated water to aquatic wildlife?

The release of hazardous elements by industrial effluents to aquatic ecosystems is a potential threat to the environment. Chromium (Cr) is one of the elements whose levels in several freshwater ecosystems should be reduced to promote water reuse. In recent years, magnetic materials have gained increasing interest as sorbents because of their easy removal from treated water through magnetic separation. In this study, colloidal cobalt ferrite (CoFe2O4) particles were investigated as magnetic sorbents for chromium-aqueous chemical species. The oxidative stress responses of Mytilus galloprovincialis mussels exposed to 200 μg/L of Cr, resembling remediated water, were evaluated. More than 95% of Cr was removed from contaminated solutions by CoFe2O4 aqueous suspensions at pH 6 and pH 10. The kinetics of sorption experiments were examined using pseudo-1st order, pseudo-2nd order and Elovich models to evaluate which mathematical model has a better adjustment to the experimental data. The present study revealed that the levels of Cr that remained in remediated water induced limited biochemical changes in mussels, being considered safe for aquatic systems. Overall, the use of cobalt ferrite-based sorbents may constitute a promising approach to remediate contaminated water.

Occurrence, fate, and potential impacts of wood preservatives in the environment: Challenges and environmentally friendly solutions

Wood preservation has gained global prevalence in recent years, primarily owing to the renewable nature of wood and its capacity to act as a carbon sink. Wood, in its natural form, lacks intrinsic resilience and is prone to decay if left untreated; hence, wood preservatives (WPs) are used to improve wood's longevity. The fate and potential hazards of wood preservatives to human health, ecosystems, and the environment are complex and depend on various aspects, including the type of the preservative compounds, their physicochemical properties, application methods, exposure pathways, environmental conditions, and safety measures and guidelines. The occurrence and distribution of WPs in environmental matrices such as soil and water can result in hazardous pollutants seeping into surface water, groundwater, and soil, posing health hazards, and polluting the environment. Bioremediation is crucial to safeguarding the environment and effectively removing contaminants through hydrolytic and/or photochemical reactions. Phytoremediation, vermicomposting, and sustainable adsorption have demonstrated significant efficacy in the remediation of WPs in the natural environment. Adsorbents derived from biomass waste have been acknowledged for their ability to effectively remove WPs, while also offering cost-efficiency and environmental sustainability. This paper aims to identify wood preservatives' sources and fate in the environment and present a comprehensive overview of the latest advancements in environmentally friendly methods relevant to the removal of the commonly observed contaminants associated with WPs in environmental matrices.

MnOx-Coffea arabica Husk and Catha edulis Leftover Biochar Nanocomposites for Removal of Methylene Blue from Wastewater

In this study, we investigated the use of manganese oxide-biochar nanocomposites (MnOx-BNC), synthesized from coffee husk (CH) and khat leftover (KL) for the removal of methylene blue (MB) from wastewater. Pristine biochars of each biomass (CH and KL) as well as their corresponding biochar-based nanocomposites were synthesized by pyrolyzing at 300°C for 1 h. The biochar-based nanocomposites were synthesized by pretreating 25 g of each biomass with 12.5 mmol of KMnO4. To assess the MB removal efficiency, we conducted preliminary tests using 0.2 g of each adsorbent, 20 mL of 20 mg·L-1 MB, pH 7.5, and shaking the mixture at 200 rpm and for 2 h at 25°C. The results showed that the pristine biochar of CH and KL removed 39.08% and 75.26% of MB from aqueous solutions, respectively. However, the MnOx-BNCs removed 99.27% with manganese oxide-coffee husk biochar nanocomposite (MnOx-CHBNC) and 98.20% with manganese oxide-khat leftover biochar nanocomposite (MnOx-KLBNC) of the MB, which are significantly higher than their corresponding pristine biochars. The adsorption process followed the Langmuir isotherm and a pseudo-second-order model, indicating favorable monolayer adsorption. The MnOx-CHBNC and MnOx-KLBNC demonstrated satisfactory removal efficiencies even after three and six cycles of reuse, respectively, indicating their potential effectiveness for alternative use in removing MB from wastewater.

Chitosan-Based Beads Incorporating Inorganic-Organic Composites for Copper Ion Retention in Aqueous Solutions

In recent years, there has been a challenging interest in developing low-cost biopolymeric materials for wastewater treatment. In the present work, new adsorbents, based on different types of chitosan (commercial, commercial chitin-derived chitosan and chitosan synthesized from shrimp shell waste) and inorganic-organic composites have been evaluated for copper ions removal. The efficacy of the synthesis of chitosan-based composite beads has been determined by studying various characteristics using several techniques, including FTIR spectroscopy, X-ray diffraction, porosimetry (N2 adsorption), and scanning electron microscopy (SEM). Adsorption kinetics was performed using different adsorption models to determine the adsorption behavior of the materials in the aqueous media. For all composite beads, regardless of the type of chitosan used, good capacity to remove copper ions from simulated waters was observed (up to 17 mg/g), which proves that the new materials hold potential for heavy metal retention. However, the adsorption efficiency was influenced by the type of chitosan used. Thus, for the series where commercial chitosan (CC) was used, the removal efficiency was approximately 29%; for the series with chitosan obtained from commercial chitin (SC), the removal efficiency was approximately 34%; for the series with chitosan enriched with CaCO3 (SH), the removal efficiency was approximately 52%.

Emerging iron-based mesoporous materials for adsorptive removal of pollutants: Mechanism, optimization, challenges, and future perspective

Iron-based materials (IBMs) have shown promise as adsorbents due to their unique physicochemical properties. This review provides an overview of the different types of IBMs, their synthesis methods, and their properties. Results found in the adsorption of emerging contaminants to a wide range of IBMs are discussed. The IBMs used were evaluated in terms of their maximum uptake capacity, with special consideration given to environmental conditions such as contact time, solution pH, initial pollutant concentration, etc. The adsorption mechanisms of pollutants are discussed taking into account the results of kinetic, isotherm, thermodynamic studies, surface complexation modelling (SCM), and available spectroscopic data. A current overview of molecular modeling and simulation studies related to density functional theory (DFT), surface response methodology (RSM), and artificial neural network (ANN) is presented. In addition, the reusability and suitability of IBMs in real wastewater treatment is shown. The review concludes with the strengths and weaknesses of current research and suggests ideas for future research that will improve our ability to remove contaminants from real wastewater streams.

Removal of heavy metals from the aqueous solution by nanomaterials: a review with analysing and categorizing the studies

With the development of nanotechnology and its application in various sciences, scientists have investigated the use of nanoparticles as adsorbents to remove heavy metals from aqueous solutions all over the world. So far, the results of many of these studies have been published in reputable journals. Obviously, reviewing these articles and summarizing the results of these studies from different aspects will provide new perspectives for the development of this technology for heavy metals removal from water. So the current study was performed to review the results of the published studies between 1/January/1980 to 1/January/2022. The focus of the study is on the analysis of these studies and their classification. In addition, a more detailed investigation was carried out. Among the 5155 articles, 576 articles were included based on Cochrane protocols. Results show that most of the studies (90.8%) were conducted on a laboratory scale and used synthetic solutions. Most studies were performed for Pb, Cd and Cu, removal respectively. Compared to other countries, authors with affiliation from China and Iran have published more articles. The ranking of the use of various nanomaterials were: nanocomposites > metal oxide nanomaterials > metal-based nanomaterials > carbon-based nanomaterials > dendrimers, with the wide range of sizes from less than 10 nm to several hundreds of nanometers. The required amount of carbon-based nanoparticles to remove many heavy metals were lower than other nanoparticles. In most studies, pH ≤ 7 has been reported as optimal. Most studies have been followed pseudo second-order and pseudo first-order reactions and have been more agreement with Langmuir and Freundlich adsorption isotherms respectively. The results of studies show that the synthesis and optimization of new nanomaterials can be considered as a new and competitive technology. However, more studies are needed to investigate the removal of heavy metals in real samples and to overcome some challenges in the full-scale application.

A review on adsorption of heavy metals from wastewater using carbon nanotube and graphene-based nanomaterials

The rampant rise in world population, industrialization, and urbanization expedite the contamination of water sources. The presence of the non-biodegradable character of heavy metals in waterways badly affects the ecological balance. In this modern era, the unavailability of getting clear water as well as the downturn in water quality is a major concern. Therefore, the effective removal of heavy metals has become much more important than before. In recent years, the attention to better wastewater remediation was directed towards adsorption techniques with novel adsorbents such as carbon nanomaterials. This review paper primarily emphasizes the fundamental concepts, structures, and unique surface properties of novel adsorbents, the harmful effects of various heavy metals, and the adsorption mechanism. This review will give an insight into the current status of research in the realm of sustainable wastewater treatment, applications of carbon nanomaterials, different types of functionalized carbon nanotubes, graphene, graphene oxide, and their adsorption capacity. The importance of MD simulations and density functional theory (DFT) in the elimination of heavy metals from aqueous media is also discussed. In addition to that, the effect of factors on heavy metal adsorption such as electric field and pressure is addressed.

Sustainable approach for adsorptive removal of cationic and anionic dyes by titanium oxide nanoparticles synthesized biogenically using algal extract ofSpirulina

Worldwide, dyes are significant pollutants present in water because of their huge consumption for industrial purposes. These dyes as pollutants cause serious health issues in human beings and cause the loss of aquatic biodiversity. So, remediation of pollutants like dyes from wastewater is the need of the hour. In the present study, we greenly synthesizedSpirulina-mediated titanium oxide nanoparticles (STONPs) for the adsorptive remediation of methyl orange (MO) (anionic) and malachite green (MG) (cationic) dyes. The characterization of STONPs was performed by Field emission scanning electron microscopy (FESEM) with EDX, FT-IR, XRD, Zeta Potential and particle size analyzer, Raman spectroscopy, and UV-vis. The various parameter effects like pH, nano-adsorbent dose, the concentration of dye, contact time, and temperature were also examined. Adsorption isotherms like Langmuir, Freundlich, and Temkin, and Kinetics models like Elovich Model, Pseudo 1st, intraparticle diffusion model (IPDM), Pseudo 2nd order, and the thermodynamic model were applied for a stronger interpretation. Theqmaxattained utilizing the Langmuir adsorption model was 272.4795 mg g-1and 209.6436 mg g-1for MO and MG correspondingly. The regeneration study of synthesized nanomaterials up to five cycles was also done. We found that greenly synthesized STONPs have great potential for adsorptive remediation for both MG and MO dyes.

Exploring the Application and Prospects of Synthetic Biology in Engineered Living Materials

At the intersection of synthetic biology and materials science, engineered living materials (ELMs) exhibit unprecedented potential. Possessing unique "living" attributes, ELMs represent a significant paradigm shift in material design, showcasing self-organization, self-repair, adaptability, and evolvability, surpassing conventional synthetic materials. This review focuses on reviewing the applications of ELMs derived from bacteria, fungi, and plants in environmental remediation, eco-friendly architecture, and sustainable energy. The review provides a comprehensive overview of the latest research progress and emerging design strategies for ELMs in various application fields from the perspectives of synthetic biology and materials science. In addition, the review provides valuable references for the design of novel ELMs, extending the potential applications of future ELMs. The investigation into the synergistic application possibilities amongst different species of ELMs offers beneficial reference information for researchers and practitioners in this field. Finally, future trends and development challenges of synthetic biology for ELMs in the coming years are discussed in detail.

Electrostatic field as an emergent technology in refining crude oils: a review

Vegetable oils and fatty acid esters (FAEs) are commonly used in various industrial and commercial applications. However, the presence of contaminants in these oils can severely affect their functionality and suitability. Conventional refining techniques for vegetable oils typically involve degumming, neutralization, bleaching and deodorization. Meanwhile, refining of FAEs often utilize wet or dry washing processes. These are often resource-intensive, producing substantial waste products, causing neutral oil loss, and can also result in the loss of micronutrients. To address these challenges, researchers have explored the use of nano-adsorbents and electrostatic field (E-field) technologies as alternatives in purifying industrial dielectric oils by removing polar particles and contaminants. Nano-adsorbents demonstrated increased efficiency in removing polar contamination while minimizing neutral oil loss. However, removal of these spent adsorbents can be challenging due to their nano-size, and physicochemical properties. The use of these materials combined with E-field technologies offers a novel and sustainable solution for removing spent nano-adsorbents and contaminants. This review provides an overview of current traditional and novel refining technologies for vegetable oils and FAEs, including their associated limitations. Compared to conventional methods, E-field treatment offers several advantages, making it an attractive alternative to conventional approaches in food processing and oil refining.

Green Synthesis of the Effectively Environmentally Safe Metakaolin-Based Geopolymer for the Removal of Hazardous Industrial Wastes Using Two Different Methods

Untreated wastewater pollution causes environmental degradation, health issues, and ecosystem disruption. Geopolymers offer sustainable, eco-friendly alternatives to traditional cement-based materials for wastewater solidification and removal. In this study, we investigate how wastewater containing organic and inorganic pollutants can be removed using geopolymer mixes based on metakaolin incorporation with cement kiln dust as an eco-friendly material. The present investigation compares the efficacy of two different techniques (solidification and adsorption) for reducing dye contaminants and heavy metals from wastewater using a geopolymer based on metakaolin incorporation with cement kiln dust. This study investigated the adsorption capacity of a geopolymer based on metakaolin incorporating two different ratios (20% and 40% by weight) of cement kiln dust (MC1 and MC2) for the reactive black 5 dyeing bath effluent (RBD) only and in a combination of 1200 mg/L of Pb²⁺ and Cd²⁺, each separately, in aqueous solutions under different adsorption parameters. The results of the adsorption technique for the two prepared geopolymer mixes, MC1 and MC2, show that MC1 has a higher adsorption activity than MC2 toward the reactive black 5 dyeing bath effluent both alone and in combination with Pb²⁺ and Cd²⁺ ions separately. The study also looked at using MC1 mix to stabilize and solidify both the dyeing bath effluent alone and its combination with 1200 mg/L of each heavy metal individually inside the geopolymer matrix for different time intervals up to 60 days of water curing at room temperature. The geopolymer matrix formed during the process was analyzed using FTIR, SEM, and XRD techniques to examine the phases of hydration products formed. The results showed that MC1 effectively adsorbs, stabilizes, and solidifies the dying bath effluent for up to 60 days, even with high heavy metal concentrations. On the other hand, geopolymer mixes showed an increase in mechanical properties when hydration time was increased to 60 days. According to our findings, the type of geopolymer developed from metakaolin and 20 wt.% cement kiln dust has the potential to be employed in the treatment of wastewater because it has good adsorption and solidification activity for the reactive black 5 dye effluent alone and for a mixture of dye pollutants with both Pb²⁺ and Cd²⁺ ions separately. Our results have significant implications for wastewater treatment and environmental remediation efforts, as they offer a sustainable solution for managing hazardous waste materials.

Arsenic contamination in groundwater and food chain with mitigation options in Bengal delta with special reference to Bangladesh

Bangladesh, situated in Bengal delta, is one of the worst affected countries by arsenic contamination in groundwater. Most of the people in the country are dependent on groundwater for domestic and irrigation purposes. Currently, 61 districts out of 64 districts of Bangladesh are affected by arsenic contamination. Drinking arsenic contaminated groundwater is the main pathway of arsenic exposure in the population. Additionally, the use of arsenic-contaminated groundwater for irrigation purpose in crop fields in Bangladesh has elevated arsenic concentration in surface soil and in the plants. In many arsenic-affected countries, including Bangladesh, rice is reported to be one of the significant sources of arsenic contamination. This review discussed scenario of groundwater arsenic contamination and transmission of arsenic through food chain in Bangladesh. The study further highlighted the human health perspectives of arsenic exposure in Bangladesh with possible mitigation and remediation options employed in the country.

Preparation of Nanocellulose-Based Aerogel and Its Research Progress in Wastewater Treatment

Nowadays, the fast expansion of the economy and industry results in a considerable volume of wastewater being released, severely affecting water quality and the environment. It has a significant influence on the biological environment, both terrestrial and aquatic plant and animal life, and human health. Therefore, wastewater treatment is a global issue of great concern. Nanocellulose's hydrophilicity, easy surface modification, rich functional groups, and biocompatibility make it a candidate material for the preparation of aerogels. The third generation of aerogel is a nanocellulose-based aerogel. It has unique advantages such as a high specific surface area, a three-dimensional structure, is biodegradable, has a low density, has high porosity, and is renewable. It has the opportunity to replace traditional adsorbents (activated carbon, activated zeolite, etc.). This paper reviews the fabrication of nanocellulose-based aerogels. The preparation process is divided into four main steps: the preparation of nanocellulose, gelation of nanocellulose, solvent replacement of nanocellulose wet gel, and drying of nanocellulose wet aerogel. Furthermore, the research progress of the application of nanocellulose-based aerogels in the adsorption of dyes, heavy metal ions, antibiotics, organic solvents, and oil-water separation is reviewed. Finally, the development prospects and future challenges of nanocellulose-based aerogels are discussed.

Recent Application Prospects of Chitosan Based Composites for the Metal Contaminants Wastewater Treatment

Heavy metals, known for their toxic nature and ability to accumulate and magnify in the food chain, are a major environmental concern. The use of environmentally friendly adsorbents, such as chitosan (CS)—a biodegradable cationic polysaccharide, has gained attention for removing heavy metals from water. This review discusses the physicochemical properties of CS and its composites and nanocomposites and their potential application in wastewater treatment.

Polyacrylonitrile support impregnated with amine-functionalized graphitic carbon nitride/magnetite composite nanofibers towards enhanced arsenic remediation: A mechanistic approach

Recently, novel composite materials are rapidly being explored for water treatment applications. However, their physicochemical behavior and mechanistic investigations are still a mystery. Therefore, our key prospect is to develop a highly stable mixed-matrix adsorbent system using polyacrylonitrile (PAN) support impregnated with amine-functionalized graphitic carbon nitride/magnetite (gCN-NH₂/Fe₃O₄) composite nanofibers (PAN/gCN-NH₂/Fe₃O₄: PCNFe) by simple electrospinning techniques. Various instrumental techniques were used to explore the structural, physicochemical, and mechanical behavior of the synthesized nanofiber. The developed PCNFe with a specific surface area of 39.0 m²/g was found to be non-aggregated and to have outstanding water dispersibility, abundant surface functionality, greater hydrophilicity, superior magnetic property, and higher thermal & mechanical characteristics making it favorable for rapid As removal. Based on the experimental findings from the batch study, 97.0 and 99.0 % of arsenite (As(III)) and arsenate (As(V)), respectively, could be adsorbed by utilizing0.02 g of adsorbent dosage within 60 min of contact time at pH 7 and 4, with an initial concentration of 10 mg/L. Adsorption of As(III) and As(V) followed the pseudo-second-order kinetic and Langmuir isotherm models with an sorption capacities of 32.26 and 33.22 mg/g, respectively, at ambient temperature. The adsorption was endothermic and spontaneous, in accordance with the thermodynamic study. Furthermore, the addition of co-anions in a competitive environment did not affect As adsorption except for PO₄^3-. Moreover, PCNFe preserves its adsorption efficiency above 80 % after five regeneration cycles. The combined results of FTIR and XPS after adsorption further support the adsorption mechanism. Also, the composite nanostructures retain their morphological and structural integrity after the adsorption process. The facile synthesis protocol, high As adsorption capacity, and enhanced mechanical integrity of PCNFe foreshadow its huge prospects for real wastewater treatment.

A review on multi-synergistic transition metal oxide systems towards arsenic treatment: Near molecular analysis of surface-complexation (synchrotron studies/modeling tools)

The science and interface chemistry between the arsenic (As) anions and the different adsorbent systems have been gaining interest in recent years in environmental remediation applications. Metal-oxides and the corresponding hybrid systems have shown promising performance as novel adsorbents in various treatment technologies. The abundance, surface chemistry, high surface area (active-centres), various synthesis and functionalization methodologies, and good recyclability make these metal oxide-based nanomaterials as potential remediating agents for As oxyanions. This work critically reviews eight different platforms focused on the arsenic contamination issue, where the first classification describes the origin of arsenic contamination and presents geographical and demo-graphical considerations. The following section briefs the state-of-the-art remediation techniques for arsenic treatment with a comparative evaluation. An emphasized discussion has been provided regarding the adsorption and classification of various metal oxide adsorbents. In the next classification, various multi-synergism abilities like Redox activity, Surface functional groups, Surface area/morphology, Heterogeneous catalysis, Reactive oxygen species, Photo-catalytic/electro-catalytic reactions, and Electrosorption are detailed. The classification of various characterization tools for accessing the arsenic remediation qualitatively and quantitatively are given in the fifth chapter. The first-of-its-kind dedicated analysis has been given on the surface complexation aspects of the arsenic speciation onto various metal adsorbent systems using synchrotron results, surface-complexation modeling, and molecular simulation (e.g., DFT) in the sixth chapter. The current sensing applications of these novel nano-material systems for arsenic determination using colorimetric and electrochemical-based analytical tools and a note about the economic parameters, i.e., regeneration aspects of various adsorbent systems/the sustainable applications of the treated sludge materials, are provided in the final sections. This work makes a critical analysis of 'Environmental Nanotechnology' towards 'Arsenic Treatment'.

Recent advances and remaining barriers to the development of electrospun nanofiber and nanofiber composites for point-of-use and point-of-entry water treatment systems

In this review, we focus on electrospun nanofibers as a promising material alternative for the niche application of decentralized, point-of-use (POU) and point-of-entry (POE) water treatment systems. We focus our review on prior work with various formulations of electrospun materials, including nanofibers of carbon, pure metal oxides, functionalized polymers, and polymer-metal oxide composites, that exhibit analogous performance to media (e.g., activated carbon, ion exchange resins) commonly used in commercially available, certified POU/POE devices for contaminants including organic pollutants, metals (e.g., lead) and persistent oxyanions (e.g., nitrate). We then analyze the relevant strengths and remaining research and development opportunities of the relevant literature based on an evaluation framework that considers (i) performance comparison to commercial analogs; (ii) appropriate pollutant targets for POU/POE applications; (iii) testing in flow-through systems consistent with POU/POE applications; (iv) consideration of water quality effects; and (v) evaluation of material strength and longevity. We also identify several emerging issues in decentralized water treatment where nanofiber-based POU/POE devices could help meet existing needs including their use for treatment of uranium, disinfection, and in electrochemical treatment systems. To date, research has demonstrated promising material performance toward relevant targets for POU/POE applications, using appropriate aquatic matrices and considering material stability. To fully realize their promise as an emerging treatment technology, our analysis of the available literature reveals the need for more work that benchmarks nanofiber performance against established commercial analogs, as well as fabrication and performance validation at scales and under conditions simulating POU/POE water treatment.

Fe(iii) and Cr(vi) ions' removal using AgNPs/GO/chitosan nanocomposite as an adsorbent for wastewater treatment

Heavy metal ions in water refer to significant risks to the biological system due to their high toxicity. Therefore, the decontamination of water polluted by heavy metal ions attracts significant interest of researchers. Adsorption by nanomaterials has been a widely used technique for removing heavy metal ions from water. Chitosan was extracted from shrimp shellfish and mixed with laboratory-prepared AgNPs/GO in the ratio of 3 : 1. A series of tests evaluates the best condition of pH, amount of adsorbent, retention time, stirring speed, temp, and initial concentration. The research was conducted under various conditions. Langmuir, Freundlich, Tempkin, and Dubinin–Radushkevich isotherms were also tested. Also, the column adsorption experiment was carried out on industrial wastewater at different flow rates and column bed heights. The optimal values of the contact time, pH, and adsorbent dose of Cr(vi) were found to be 80 min, 4, and 0.1 g 100 mL⁻¹, respectively, at room temperature (30 °C), agitation at 150 rpm, and initial concentration of 50 ppm. On the other hand, the optimal value of contact time, pH, and adsorbent dose of Fe(iii) were found to be 30 min, 6, and 0.02 g 100 mL⁻¹, respectively, at room temp (30 °C) with a stirring speed of 250 rpm and an initial concentration of 40 ppm. For Cr(vi) and Fe(iii), equilibrium studies show that the data fit the Freundlich isotherm well (correlation coefficient, R² = 0.98) (III). A link between the pseudo-second order active model and data fitting the pseudo-first order active models were made. Within the intraparticle diffusion model, there are four stages that the mechanism must go through before it is at equilibrium. The adsorbent was tested in an industrial adsorbent column. This test proves that the nanocomposite's adsorption capacity can be restored by washing it with 0.1 M HCl, as shown by the periodicity test. After four cycles, the amount of Cr(vi) adsorbed on AgNPs/GO/chitosan was just 20%, which is insufficient for further adsorption experiments. Cr(vi) removal rates (%R) decreased slightly.

Steps of AgNPs/GO/chitosan nanocomposite preparation.

Nanostructured Materials for Water Purification: Adsorption of Heavy Metal Ions and Organic Dyes

Chemical water pollution poses a threat to human beings and ecological systems. The purification of water to remove toxic organic and inorganic pollutants is essential for a safe society and a clean environment. Adsorption-based water treatment is considered one of the most effective and economic technologies designed to remove toxic substances. In this article, we review the recent progress in the field of nanostructured materials used for water purification, particularly those used for the adsorption of heavy metal ions and organic dyes. This review includes a range of nanostructured materials such as metal-based nanoparticles, polymer-based nanomaterials, carbon nanomaterials, bio-mass materials, and other types of nanostructured materials. Finally, the current challenges in the fields of adsorption of toxic materials using nanostructured materials are briefly discussed.

Development of Efficient Photocatalyst MIL-68(Ga)_NH2 Metal-Organic Framework for the Removal of Cr(VI) and Cr(VI)/RhB from Wastewater under Visible Light

Severe environmental pollution is caused by the massive discharge of complex industrial wastewater. The photocatalytic technology has been proved as an effective way to solve the problem, while an efficient photocatalyst is the most critical factor. Herein, a new photocatalyst MIL-68(Ga)_NH₂ was obtained by hydrothermal synthesis and were characterized by PXRD, FTIR, ¹H NMR, and TGA systematically. The result demonstrates that MIL-68(Ga)_NH₂ crystallized in orthorhombic system and Cmcm space group with the unit cell parameters: a = 36.699 Å, b = 21.223 Å, c = 6.75 Å, V = 5257.6 ų, which sheds light on the maintenance of the crystal structure of the prototype material after amino modification. The conversion of Cr(VI) and binary pollutant Cr(VI)/RhB in wastewater under visible light stimulation was characterized by the UV-vis DRS. Complementary experimental results indicate that MIL-68(Ga)_NH₂ exhibits remarkable photocatalytic activity for Cr(VI) and the degradation rate reaches as high as 98.5% when pH = 2 and ethanol as hole-trapping agent under visible light irradiation with good reusability and stability. Owing to the synergistic effect between Cr(VI) and RhB in the binary pollutant system, MIL-68(Ga)_NH₂ exhibits excellent catalytic activity for both the pollutants, the degradation efficiency of Cr(VI) and RhB was up to 95.7% and 94.6% under visible light irradiation for 120 min, respectively. The possible removal mechanism of Cr(VI)/RhB based on MIL-68(Ga)_NH₂ was explored. In addition, Ga-based MOF was applied in the field of photocatalytic treatment of wastewater for the first time, which broadened the application of MOF materials in the field of photocatalysis.

Novel design of amine and metal hydroxide functional group modified onto sludge biochar for arsenic removal

This study involved novel-designed sludge biochar (SB) adsorbed for arsenic removal with lower operating costs and higher adsorption efficiency properties. Generally, biochar only relies on micropores for pollutant adsorption, but physical adsorption is not highly efficient for arsenic removal. Therefore, in order to improve the removal efficiency of arsenic by SB, diethylenetriamine (DETA) and FeCl₃ were used in this study to modify the surface of SB by an immersion method. The objectives of this research are to obtain optimum operation conditions by assessing the effect of different Fe content, pH and initial concentration on adsorbing arsenic. This study is the first to use Density Functional Theory (DFT) to simulate and verify the adsorption mechanism of arsenic by SB. Results showed the presence of amine/iron oxyhydroxides functional groups greatly promoted SB surface activity and its arsenic adsorption potential. The surface area, pore volume and pore size of the SB were estimated to be 525 m² g^-1, 0.35 cm³ g^-1 and 8.71 nm, respectively. The DFT model result is the same as the result of arsenic adsorption performance with high adsorption energy (-246.3 kJmol^-1) and shorter bond distances (1.42 Å), indicating strong chemical adsorption between arsenic and material. The reaction mechanism is divided into four pathways, including oxidation-reduction, complexation, electrostatic adsorption and pore adsorption.

A comprehensive review on nanobiotechnology for bioremediation of heavy metals from wastewater

Removal of contaminants from wastewater is a big concern for the scientific community. Heavy metals are one of the major contaminants present in wastewater. Heavy metals such as Cd²⁺ , Pb²⁺ , Mn²⁺ , and so forth, are highly toxic and pose a serious threat to the environment due to their nonbiodegradable nature. With the advent of nanobiotechnology, heavy metal contaminants can be mitigated with the help of nanomaterials produced by eco-friendly methods. Specially designed bionanomaterials often exhibit properties such as increased shelf life, self-healing nature, adaptability in different environments, and cost-effectiveness, thus showing advantages over nanomaterials produced by physicochemical methods. Due to their high specificity and adsorption capacity, bionanomaterials can remove heavy metals present even in a very low concentration in wastewater. The use of bionanotechnology in their remediation paves a way for environmental sustainability and helps in cost reduction. This paper intends to discuss the nanobiotechnological approach for the remediation of heavy metals from wastewater. Furthermore, the paper also reviews some important nanomaterials and their potential applications in the depollution of heavy-metal contaminated wastewater.

Advancements in heavy metals removal from effluents employing nano-adsorbents: Way towards cleaner production

Due to the development in science field which gives not only benefit but also introducesundesirable pollution to the environment. This pollution is due to poor discharge activities of industrial effluents into the soil and water bodies, surface run off from fields of agricultural lands, dumping of untreated wastes by municipalities, and mining activites, which deteriorates the cardinal virtue of our environment and causes menace to human health and life. Heavy metal(s), a natural constituent on earth's crust and economic important mineral, due to its recalcitrant effects creates heavy metal pollution which affects food chain and also reduces the quality of water. For this, many researchers have performed studies to find efficient methods for wastewater remediation. One of the most promising methods from economic point of view is adsorption, which is simple in design, but leads to use of a wide range of adsorbents and ease of operations. Due to advances in nanotechnology, many nanomaterials were used as adsorbents for wastewater remediation, because of their efficiency. Many researchers have reported that nanoadsorbents are unmitigatedly a fruitful solution to address this world's problem. This review presents a potent view on various classes of nanoadsorbents and their application to wastewater treatment. It provides a bird's eye view of the suitability of different types of nanomaterials for remediation of wastewater and Backspace gives up-to-date information about polymer based and silica-based nanoadsorbents.

Metal(loid) nanosorbents in restoration of polluted soils: geochemical, ecotoxicological, and remediation perspectives

Nowadays, the applications of nanomaterials (NMs) are becoming the edge over others and referred as one of the pillars of emerging science and technology. Thereby, a wide array of NMs have been developed along with the products that can be used for the reclamation of contaminated terrestrial ecosystems. The NMs got a great consideration due to their peculiar characteristics and high efficacy. Therefore, this review addresses in depth the ability of metal(loid) NMs as nanosorbents along with their applications in soil remediation. Adsorption is commonly employed for the elimination of innumerable contaminants because of low expenses, reliability, and convenience. The first emphasis of this work will be the use of nanoscale meta(loid) adsorbents for contaminated soil remediation along with their geochemistry. Because NMs mediated soil remediation promises more efficient and cost-effective than conventional methods and can enhance the probability of in situ contaminants remediation. However, the extensive usage of NMs is enhancing their concentrations in the environment and get a route to enter the surrounding flora and fauna that can induce serious concerns due to the lack of absolute understanding regarding NMs interactions with living organisms. Therefore, the second focus of this work will be on the ecotoxicological impacts with special attentions on morpho-physiological alterations in edible plants.

Remediation of arsenic-contaminated soil by nano-zirconia modified biochar

Nowadays, the soil arsenic pollution is considered as a serious environmental issue, and the high toxicity of arsenic can seriously affect the quality and safety of agricultural products and human health. Biochar, as a solidifying/passivating agent, has been widely used in the treatment of soil heavy metal pollution. Pine biochar (BC) was used as a carrier in this study, and biochar-loaded nano-zirconia (N-ZrO₂-BC) was synthesized to investigate its adsorption and fixation characteristics on As (V) in soil and water. The adsorption experiment showed that the second-order kinetic equation had a good fitting effect on the adsorption curve of As (V) on the N-ZrO₂-BC surface, which indicated that chemical adsorption was the main factor controlling the reaction rate. FTIR and SEM results showed that ion exchange and surface complexation were the main mechanisms of As (V) adsorption by N-ZrO₂-BC. Soil culture experiments showed that the stabilization efficiency of arsenic in soil with 2% N-ZrO₂-BC reached 99.30% after 60 days, and the extractable arsenic content was reduced to 3.07 μg·L^-1, which reached the quality standard of class III groundwater (<0.01 mg·L^-1, GB/T 14848-2017). Comparing with the control, the content of acid extractable arsenic in soil decreased by 90.57%, and the residual arsenic increased by 51.46%, indicating that the addition of N-ZrO₂-BC could effectively promote the transformation of active arsenic to stable arsenic in soil.

Adsorption Configurations of Iron Complexes on As(III) Adsorption Over Sludge Biochar Surface

Waste recycling and reuse will result in significant material and energy savings. In this research, usage of hospital sludge as a biochar adsorbent for wastewater treatment plants was investigated. Microwave carbonization was used to carbonize the sludge and then chemically activated with ZnCl₂to increase surface area and porosity. A newly designed iron metal doped sludge biochar carbon (SBC) has effective adsorption of inorganic arsenic (As(III), As₂O₃) in water. The findings clearly demonstrate the viability and utility of using hospital sludge as a source of carbon to generate SBC. The adsorption mechanism of As(III) on SBC's iron-metal-modified surface has been studied using density functional theory (DFT) to understand the impact of functional complexes on adsorption As(III). Tests showed physical as well as chemical adsorption of As(III) on Fe-SBC surface. Fe's involvement in functional complexes greatly fostered SBC surface activity and it's As(III) adsorption ability. The physical adsorption energies of As(III) with Fe functional complexes on the SBC surface were -42.3 KJ mol^-1. Other hand, the chemical adsorption energies of As(III) on Fe-SBC surface was -325.5 KJ mol^-1. As(III) is capable of interacting in a bidentate fashion with the dopants through the protonated oxygen atoms and this conformation of the cyclic structure is higher in the adsorption energy than the others.

Heavy metal pollution and the role of inorganic nanomaterials in environmental remediation

Contamination of water and soil with toxic heavy metals is a major threat to human health. Although extensive work has been performed on reporting heavy metal pollutions globally, there are limited review articles on addressing this pernicious phenomenon. This paper reviews inorganic nanoparticles and provides a framework for their qualities required as good nanoadsorbents for efficient removal of heavy metals from water. Different inorganic nanoparticles including metals, metal oxides and metal sulfides nanoparticles have been applied as nanoadsorbents to successfully treat water with high contaminations of heavy metals at concentrations greater than 100 mg l^-1, achieving high adsorption capacities up to 3449 mg g^-1. It has been identified that the synthesis method, selectivity, stability, regeneration and reusability, and adsorbent separation from solution are critical parameters in deciding on the quality of inorganic nanoadsorbents. Surface functionalized nanoadsorbents were found to possess high selectivity and capacity for heavy metals removal from water even at a very low adsorbent dosage of less than 2 g l^-1, which makes them better than conventional adsorbents in environmental remediation.

Eco-Friendly Ferrimagnetic-Humic Acid Nanocomposites as Superior Magnetic Adsorbents

Recyclable, cheap, eco-friendly, and efficient adsorbent materials are very important for the removal of pollution. In this work, we report the design and implementation of ferrimagnetic-humic acid nanocomposites as superior magnetic adsorbent for heavy metals. Ferrimagnetic and ferrimagnetic-humic acid nanocomposite particles with different morphologies were prepared using the coprecipitation method and hydrothermal synthesis method, respectively. The results show that the morphology of the nanoparticles prepared by the coprecipitation method is more uniform and the size is smaller than that by the hydrothermal synthesis method. Adsorption experiments show that the ferrimagnetic-humic acid nanoparticles prepared by the coprecipitation method has high sorption capacity for cadmium, and the maximum adsorption capacity is about 763 μg/g. At the same time, magnetic technology can be used to realize the recycling of ferrimagnetic-humic acid adsorbents.

Impact of Cations (Na+, K+, Mg+2) and Anions (F-, Cl-, SO42-) Leaching from Filters Packed with Natural Zeolite and Ferric Nanoparticles for Wastewater Treatment

Natural zeolites have been employed to adsorb contaminants in water. This study is aimed to evaluate the cation and anion leaching from the zeolite after the wastewater was passed through filters packed with a natural zeolite (heulandite-CaAl₂Si₇O₁₈·6H₂O). Eight treatments were evaluated in a 2 × 2 × 2 factorial treatment design. Factor A was the zeolite with two levels: 127 g and 80.4 g. Factor B was the nanoparticles with two levels: one bag (3.19 g) and two bags (6.39 g); and Factor C was the use of a magnet: with and without. There were two replications; hence, a total of 16 filters were employed. The water was obtained from a municipal wastewater treatment plant (MWTP). The cations (Na⁺, K⁺; Mg⁺² and Ca⁺²) and anions (F⁻, Cl⁻ and SO₄²⁻) were measured before (influent = IW) and after filtering (effluent = EW) three times. All treatments leached the cations Na⁺ (EW in a range of 175 to 232 ppm), K⁺ (EW in a range of 15.4 to 33.2 ppm), and Mg⁺² (EW in a range of 7.40 to 10.8 ppm) but did not leach Ca⁺². Likewise, the treatments leached the anions F⁻ (EW in a range of 7.59 to 8.87 ppm), Cl⁻ (EW in a range of 85.9 to 120 ppm), and SO₄²⁻ (EW in a range of 139 to 146 ppm). We conclude that this natural zeolite leaches cations (except Ca⁺²) and anions in MWTP passed through filters. Therefore, its application in wastewater treatment should be considered for purposes such as agriculture and animal production and not for drinking water.

Nano-adsorbents an effective candidate for removal of toxic pharmaceutical compounds from aqueous environment: A critical review on emerging trends

Advancements in medical research has resulted in the modernization of healthcare facilities, subsequently leading to a higher level of production and usage of pharmaceuticals to sustain better quality of life. Pharmaceutical active compounds (PhACs) possess high genotoxicity and eco-toxicity thus presenting numerous side effects to living beings on long-term exposure. The fate and toxicity of PhACs were explored in detail, aiming to elucidate their occurrence and transmission in wastewater treatment systems (WWTPs). Adsorption of pharmaceutical compounds using Nano-adsorbents has gained momentum in recent years owing to their low-cost, high surface area and effectiveness. This review has been conducted in order to widen the utilization of Nano adsorbents in the adsorption of pharmaceutical compounds with a focus on the aqueous environment. The synthesis routes and properties of Nano-adsorbents for removal of PhACs were assessed in a comprehensive way. The recovery and reuse ability of nano-adsorbents also forms an integral part of its application in the removal of PhACs and has hence been delineated.

Sustainable Removal of Contaminants by Biopolymers: A Novel Approach for Wastewater Treatment. Current State and Future Perspectives

Naturally occurring substances or polymeric biomolecules synthesized by living organisms during their entire life cycle are commonly defined as biopolymers. Different classifications of biopolymers have been proposed, focusing on their monomeric units, thus allowing them to be distinguished into three different classes with a huge diversity of secondary structures. Due to their ability to be easily manipulated and modified, their versatility, and their sustainability, biopolymers have been proposed in different fields of interest, starting from food, pharmaceutical, and biomedical industries, (i.e., as excipients, gelling agents, stabilizers, or thickeners). Furthermore, due to their sustainable and renewable features, their biodegradability, and their non-toxicity, biopolymers have also been proposed in wastewater treatment, in combination with different reinforcing materials (natural fibers, inorganic micro- or nano-sized fillers, antioxidants, and pigments) toward the development of novel composites with improved properties. On the other hand, the improper or illegal emission of untreated industrial, agricultural, and household wastewater containing a variety of organic and inorganic pollutants represents a great risk to aquatic systems, with a negative impact due to their high toxicity. Among the remediation techniques, adsorption is widely used and documented for its efficiency, intrinsic simplicity, and low cost. Biopolymers represent promising and challenging adsorbents for aquatic environments’ decontamination from organic and inorganic pollutants, allowing for protection of the environment and living organisms. This review summarizes the results obtained in recent years from the sustainable removal of contaminants by biopolymers, trying to identify open questions and future perspectives to overcome the present gaps and limitations.

TiO2/rectorite-trapped cellulose composite nanofibrous mats for multiple heavy metal adsorption

The anthropogenic release of highly toxic heavy metals into the environment presents a huge challenge for ecosystems and human society. Recoverable and efficient adsorption materials could be obtained by trapping inorganic adsorbents (e.g., TiO₂ nanoparticles and rectorite (REC)), in a natural polymer matrix. In this study, a series of cellulose-TiO₂/REC composite nanofibrous mats were fabricated via electrospinning. The interactions between inorganic adsorbents and cellulose molecules improved the thermal stability, surface area, tensile strength and adsorption capacity of the mats. We focused on the adsorption of Pb²⁺, Cu²⁺ and Cd²⁺ from acidic solutions onto cellulose-TiO₂/REC composite nanofibrous mats in multiple systems because the magnitudes of heavy metal concentrations in wastewater typically varied. The maximum total adsorption capacity of 69.81 mg/g was obtained by Cellulose-TiO₂/REC_2:1 nanofibrous mats. The composite nanofibrous mats successfully trapped TiO₂ nanoparticles, and the obtained cellulose-TiO₂/REC nanofibrous mats could be used to remove heavy metals from acidic wastewater.