Selective removal of Cu(II) ions by using cation-exchange resin-supported polyethyleneimine (PEI) nanoclusters

Well-designed protein amyloid nanofibrils composites as versatile and sustainable materials for aquatic environment remediation: A review

Amyloid nanofibrils (ANFs) are supramolecular polymers originally classified as pathological markers in various human degenerative diseases. However, in recent years, ANFs have garnered greater interest and are regarded as nature-based sustainable biomaterials in environmental science, material engineering, and nanotechnology. On a laboratory scale, ANFs can be produced from food proteins via protein unfolding, misfolding, and hydrolysis. Furthermore, ANFs have specific structural characteristics such as a high aspect ratio, good rigidity, chemical stability, and a controllable sequence. These properties make them a promising functional material in water decontamination research. As a result, the fabrication and application of ANFs and their composites in water purification have recently gained considerable attention. Despite the large amount of literature in this field, there is a lack of systematic review to assess the gap in using ANFs and their composites to remove contaminants from water. This review discusses significant advancements in design techniques as well as the physicochemical properties of ANFs-based composites. We also emphasize the current progress in using ANFs-based composites to remove inorganic, organic, and biological contaminants. The interaction mechanisms between ANFs-based composites and contaminants are also highlighted. Finally, we illustrate the challenges and opportunities associated with the future preparation and application of ANFs-based composites. We anticipate that this review will shed new light on the future design and use of ANFs-based composites.

Effectiveness of Opuntia ficus indica (cactus) fruit juice for sludge conditioning

The possibility of using Opuntia ficus indica fruit juice (OFIFJ) as a bioflocculant for conditioning the synthetic kaolin sludge and sewage sludge (region Oran, Algeria, and Pau, France) was studied. Turbidity of the supernatant, dryness of the sludge cake, and total time of filtration (TTF) were examined parameters. Using vacuum filtration, lime was also tested as a chemical conditioner and gives good results on Lescar (France) sewage sludge in terms of cake's dryness, filtrate quality, turbidity (13.54%), and total time of filtration (TTF = 85.29%), comparing to the industrial polymer (Sedifloc 408C; turbidity; 8.33% and TTF: 2.94%). For the sewage sludge of Oran (Algeria), the results obtained with OFIFJ were compared to those obtained with the cladodes juice of the same plant OFIC, and also with a cationic polymer (Superfloc 8396). For an optimum dosage, it showed that OFIFJ has a flocculation activity as same as the cladodes juice OFIC for sludge conditioning and gives better results in terms of turbidity (dosage of 22.4 g/kg DM: 3.7 NTU for OFIC, dosage of 8.36: 3.63 NTU for OFIFJ. Dryness was enhanced from 14.91 to 22.93% (OFIC 16 g/kg DM) and to 24.48% (OFIF 20.9 g/kg DM) but for TTF, we found the opposite. In fact, this plant showed to be an available, biodegradable, and non-toxic flocculant. For kaolin synthetic sludge (30%), the optimum dosages of those conditioners were found to be 0.066 g kg-1 for OFIC, comparing between vacuum filtration and filtration compression; turbidity was enhanced for both techniques, contrary to dryness. Concerning the Oran city sewage sludge, both turbidity and dryness were optimized. Same thing for the France sewage sludge, all the studied parameters were enhanced with the two studied bioflocculants.

Advances in the adsorption of heavy metal ions in water by UiO-66 composites

The innovative adsorbents known as the Metal-organic Framework (MOFs) had a high specific surface area, various structural types, and good chemical stability. MOFs have been produced through hydrothermal, mechanochemical, microwave-assisted, gelation, and other synthesis methods, and the solvothermal process is one of them that researchers frequently utilize. The UiO materials have a more comprehensive application potential than different subtypes of MOFs among the numerous MOFs that have been synthesized. The synthesis of MOFs and their composites, as well as the adsorption characteristics of UiO materials in the adsorption of various heavy metal ions, have all been examined and summarized in this study.

Electrospun Nanofiber Membrane: An Efficient and Environmentally Friendly Material for the Removal of Metals and Dyes

With the rapid development of nanotechnology, electrospun nanofiber membranes (ENM) application and preparation methods have attracted attention. With many advantages such as high specific surface area, obvious interconnected structure, and high porosity, ENM has been widely used in many fields, especially in water treatment, with more advantages. ENM solves the shortcomings of traditional means, such as low efficiency, high energy consumption, and difficulty in recycling, and it is suitable for recycling and treatment of industrial wastewater. This review begins with a description of electrospinning technology, describing the structure, preparation methods, and factors of common ENMs. At the same time, the removal of heavy metal ions and dyes by ENMs is introduced. The mechanism of ENM adsorption on heavy metal ions and dyes is chelation or electrostatic attraction, which has excellent adsorption and filtration ability for heavy metal ions and dyes, and the adsorption capacity of ENMs for heavy metal ions and dyes can be improved by increasing the metal chelation sites. Therefore, this technology and mechanism can be exploited to develop new, better, and more effective separation methods for the removal of harmful pollutants to cope with the gradually increasing water scarcity and pollution. Finally, it is hoped that this review will provide some guidance and direction for research on wastewater treatment and industrial production.

“Gamma Irradiation Synthesis of Carboxymethyl Chitosan-Nanoclay Hydrogel for the Removal of Cr(VI) and Pb(II) from Aqueous Media”

Hydrogel composites comprised of N,O carboxymethyl chitosan crosslinked with different weight ratios of acrylic acid and fabricated with nanoclay particle were prepared via gamma irradiation at 25 kGy irradiation dose. The prepared composites were coded as CsAA1Cl, CsAA2Cl and CsAA3Cl based on the weight ratio of acrylic acid to the chitosan derivative. The claimed hydrogels were characterized by FTIR, TGA and XRD. The TGA data implied that the incorporation of clay nanoparticles enhanced the thermal stability of the composites; the decomposition temperature increased up to 500 °C for CsAA3Cl. Three AFM outcomes were used to compare the surface features of the samples; topography, height and surface roughness. The topography data reveals that the nanoclay particles incorporated in CsAA3Cl are intercalated and exfoliated. Then, the optimized sorbent (CsAA3Cl) was investigated as green sorbents for chromium (VI) and lead (II). The data revealed that CsAA3Cl displayed maximum removal performance towards both lead and chromium with removal efficiencies 125 mg/g and 205 mg/g respectively at the optimum application conditions within 90 min only. Also, it was found that the optimum pH value was 9 for chromium and 8 for lead. The data proved that the adsorption of both cations followed pseudo-first order kinetic model. The prepared composites showed acceptable metal uptake capacity at three successive cycles.

Graphical Abstract

Super-adsorbent microspheres based on a triallyl isocyanurate-maleic anhydride copolymer for the removal of organic pollutants from water

Owing to the frequent occurrence of diclofenac sodium (DS) in fresh aquatic environments and its potential toxicity towards living organisms, the effective removal of DS has attracted worldwide attention. Herein, a green and efficient strategy to fabricate crosslinked microspheres with interconnected mesoporous structures and abundant adsorption active sites was developed. With this strategy, triallyl isocyanurate (TAIC)-maleic anhydride (MAH) copolymer microspheres (TMs) with a diameter of 1.19-1.35 μm were first prepared by self-stabilized precipitation (2SP) polymerization, and the TMs possess a large amount reactive anhydride groups (62.5-71.8 mol%), a specific surface area of 51.6-182.4 m² g^-1 and a mesoporous structure (average pore size: 3.4-3.8 nm). Then the TMs were further functionalized with polyethylenimine (PEI) to give rise to cationic microspheres (Cat-TMs), which showed excellent adsorption performance to DS with a rapid adsorption rate (reached equilibrium within 30 min), a very high equilibrium adsorption capacity (1421 mg g^-1) and excellent recyclability. The pseudo-second-order model and Langmuir model were a good fit for the adsorption kinetic and isotherm process, respectively. Furthermore, due to the high cation density (4.291 mmol g^-1) and excellent pH buffer capacity of Cat-TMs, the adsorption capacity can be maintained at a high level within the pH range of 6-10. The regenerated Cat-TMs showed only a slight loss (<5%) in the adsorption capacity even after 5 adsorption-desorption cycles. In short, Cat-TMs can be considered as a highly promising adsorbent for the rapid and ultra-efficient removal of anionic organic contaminants and have significant potential to be applied in wastewater treatment.

Environmental application of amine functionalised magnetite nanoparticles grafted graphene oxide chelants

This study proposed a two-step method involving hydrothermal and electrostatic self-assembly processes for synthesising an amine-functionalised magnetic ligand graphene oxide-based nanocomposite (EDTA@Fe₃O₄@GO). The amine groups were successfully attached to the surface of iron (II, III) oxide (Fe₃O₄), which were embedded on the surface of graphene oxide (GO) (Fe₃O₄@GO). This EDTA@ Fe₃O₄@GO nanocomposite was used as a chelating agent to bind the toxic heavy metal ions. EDTA@Fe₃O₄@GO demonstrated the synergistic effect between the large surface area and magnetic behaviour of Fe₃O₄@GO and the chelating effect of EDTA, and it showed higher efficiency than the individual GO and Fe₃O₄. The possible structural and compositional characteristics were proposed based on Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET) and Raman spectroscopy analysis. The outcomes revealed the mechanism behind the excellent As(V) adsorption onto EDTA@Fe₃O₄@GO. The adsorption process was studied by fitting the experimental data obtained into various kinetic and isotherm models. The pseudo-second-order (PSO) kinetic model and the Freundlich isotherm model (FIM) were found to be the best fit models for the removal of As(V) by EDTA@Fe₃O₄@GO. EDTA@Fe₃O₄@GO has the utmost adsorption capacity of 178.4 mg/g. Furthermore, the EDTA@Fe₃O₄@GO nanocomposite is reusable, and it showed excellent adsorption capacity up to 5 cycles. This study has provided insight into the potential of EDTA@Fe₃O₄@GO and its applications in large-scale wastewater treatment.

Inferences on metal pollution in the natural spawning zone of Bangladesh river and pollution management strategies

The purpose of this study was to evaluate the metal concentrations in the Halda River in Bangladesh to determine the quality of the water and sediment in the natural spawning zone. Fe > Zn > Cr > Cd > Cu was the order of the metals in water, whereas Fe > Zn > Cd > Cu was the order in sediments. Almost all of the heavy metals in the water and sediment had been found within the established limits, with the exception of Cr and Fe in the river and Cu in the sediment. In the case of water, Cr vs. Zn was found to have the strongest correlation (r = 0.96). Due to the coagulation and adsorption processes, it was shown that Fe and Zn had a substantial correlation of 0.96, Cu and Cd of 0.91, and Cr of 0.78 with Zn. Hazard quotient values of Cd show the not potable nature of Halda river surface water and might give adverse health effects for all age groups except Cu and Zn. Pollution load index values indicated the uncontaminated nature of the river bottom sediments. Natural and human activities were the key factors influencing the accumulation and movement of heavy metals in the water and sediments. Contamination sources are industrial effluents, garbage runoff, farming operations, and oil spills from fishing vessels which are comparable according to multivariate statistical analysis. Ion exchange, absorption, precipitation, complexation, filtration, bio-absorption, redox reaction, and reverse osmosis were considered to be effective for the degradation of metal concentrations. The feasibility of the suggested metal reduction procedures has to be studied to know which is optimally appropriate for this river region. It is expected that this study could provide a useful suggestion to decrease the metal pollution in the river.

Health Risk of Ingested Heavy Metals in Fluidized Canned Milks: Are We Drinking Heavy Metals?

This study examined the heavy metal level of canned milk consumed in Calabar, Cross River State, as well as the health risks linked to it. Peak Milk, Three Crown, Coast, Nunu, Cowbell, and Olympic milk types were chosen for research. During the digestion of samples, 0.5 mol of nitric acid was added to the sample and heated. The heated liquid was slowly heated with 2.5 mL of 70% HClO4 until a dense white vapor was formed. After cooling the mixture, 10 mL of deionized water was added and the solution was boiled to expel the fumes. The heavy metals were screened using an atomic absorption spectrophotometer. All milk samples contained eight heavy metals: iron (Fe), copper (Cu), zinc (Zn), arsenic (As), lead (Pb), cadmium (Cd), manganese (Mn), and nickel (Ni). Peak Milk and Nunu both had Cd. Nickel was found in various quantities in Coast, Cowbell, Nunu, and Olympic. Coast, Nunu, and Cowbell samples all contained Mn. Nunu and Cowbell both tested positive for lead. Peak Milk did not contain copper (Cu). Standard models for daily consumption of different heavy metals, such as Pb in Nunu (3.7E − 03) and Cowbell (−1.8E − 03), were used to construct the health risk evaluations. Peak Milk, Three Crown, and Nunu had daily Cd intakes of (4.5E − 06), (2.2E − 05), and (4.5E − 06), respectively. Coast (3.2E − 02), Nunu (5.1E − 02), Cowbell (1.9E − 02), and Olympic (3.8E − 02) have different daily Ni intakes. Peak Milk (1.1E − 01), Three Crown (2.2E − 01), Coast (1.6E − 01), Nunu (7.1E − 01), Cowbell (1.4E − 01), and Olympic (1.1E − 01) have different daily intakes of Ar. Peak (6.0E − 04), Three Crown (8.0E − 04), Coast (6.0E − 04), Nunu (7.0E − 04), Cowbell (8.0E − 04), and Olympic (6.0E − 04) had different daily Zn intakes. Daily Fe intakes of Peak Milk was (1.6E − 01), Three Crown was (1.6E − 01), Coast was (1.4E − 01), Nunu was (1.4E − 01), Cowbell was (2.4E − 01), and Olympic was (1.8E − 01). Cu intakes per day for Three Crown, Coast, Nunu, Cowbell, and Olympic were (6.0E − 03), (4.0E − 03), (2.0E − 03), (2.0E − 03), and (4.0E − 03), respectively. Coast, Nunu, and Cowbell had daily Mn intakes of (2.0E − 04), respectively. The total hazard index (THI) and the target hazard quotient (THQ) were also calculated. Peak Milk (1.7E − 01), Three Crown (3.4E − 01), Coast (2.8E − 01), Nunu (1.9E − 01), Cowbell (2.4E − 01), and Olympic (2.3E − 01) induced cancer risks, accordingly. According to the findings, the risk of drinking milk is relatively considerable when compared to the acceptable limit.

Enhancement on the degradation of naproxen in Cu0 activated peroxymonosulfate system by complexing reagents

In recent years, there has been growing interest in the mechanism (radical or nonradical) of persulfate activation processes. In this study, the enhancement of naproxen (NPX) degradation in a Cu⁰/peroxymonosulfate (PMS) system by complexing reagents was investigated. Surprisingly, neocuproine (NCP) alters the nature of reactive species in the Cu⁰/PMS system. A high-valent copper species, Cu(III)-NCP, was found to dominate NPX degradation rather than radicals under acid conditions for the first time. Moreover, systematically designed experiments revealed that the Cu(III)-NCP complex was a strong selective oxidant that reacted with organics through a single electron transfer pathway. Meanwhile, the degradation efficiency of NPX was highly dependent on the solution pH and dosage of Cu⁰ and NCP, but was irrelevant to the concentration of NPX. Additionally, the enhancement of NCP on other copper based PMS activation systems (i.e., Cu²⁺/HA/PMS and Cu⁰/HA/PMS systems) was investigated. Considering that the released copper can be removed by a simple precipitation method to meet the effluent standards, the new complex-enhanced Cu⁰/PMS system provided a new method to enhance the degradation efficiencies of pollutants by a copper-catalyzed Fenton-like system.

Sustainable and efficient technologies for removal and recovery of toxic and valuable metals from wastewater: Recent progress, challenges, and future perspectives

Due to their numerous effects on human health and the natural environment, water contamination with heavy metals and metalloids, caused by their extensive use in various technologies and industrial applications, continues to be a huge ecological issue that needs to be urgently tackled. Additionally, within the circular economy management framework, the recovery and recycling of metals-based waste as high value-added products (VAPs) is of great interest, owing to their high cost and the continuous depletion of their reserves and natural sources. This paper reviews the state-of-the-art technologies developed for the removal and recovery of metal pollutants from wastewater by providing an in-depth understanding of their remediation mechanisms, while analyzing and critically discussing the recent key advances regarding these treatment methods, their practical implementation and integration, as well as evaluating their advantages and remaining limitations. Herein, various treatment techniques are covered, including adsorption, reduction/oxidation, ion exchange, membrane separation technologies, solvents extraction, chemical precipitation/co-precipitation, coagulation-flocculation, flotation, and bioremediation. A particular emphasis is placed on full recovery of the captured metal pollutants in various reusable forms as metal-based VAPs, mainly as solid precipitates, which is a powerful tool that offers substantial enhancement of the remediation processes' sustainability and cost-effectiveness. At the end, we have identified some prospective research directions for future work on this topic, while presenting some recommendations that can promote sustainability and economic feasibility of the existing treatment technologies.

A Review: Adsorption and Removal of Heavy Metals Based on Polyamide-amines Composites

In recent years, the problem of heavy metal pollution has become increasingly prominent, so it is urgent to develop new heavy metal adsorption materials. Compared with many adsorbents, the polyamide-amine dendrimers (PAMAMs) have attracted extensive attention of researchers due to its advantages of macro-molecular cavity, abundant surface functional groups, non-toxicity, high efficiency and easy modification. But in fact, it is not very suitable as an adsorbent because of its solubility and difficulty in separation, which also limits its application in environmental remediation. Therefore, in order to make up for the shortcomings of this material to a certain extent, the synthesis and development of polymer composite materials based on PAMAMs are increasingly prominent in the direction of solving heavy metal pollution. In this paper, the application of composites based on PAMAMs and inorganic or organic components in the adsorption of heavy metal ions is reviewed. Finally, the prospects and challenges of PAMAMs composites for removal of heavy metal ions in water environment are discussed.

Adsorption properties and recognition mechanisms of a novel surface imprinted polymer for selective removal of Cu(II)-citrate complexes

Cu(II)-citrate (Cu(II)-CA) complex, as one of the components in plating solutions, increases the difficulty of Cu(II) treatment due to its stable structure and high mobility. In this work, a novel surface imprinted polymer (Cu-CA-SIP) for selective removal of Cu(II)-CA complex from aqueous solution is synthesized by using polyethyleneimine (PEI) grafted onto chloromethylated polystyrene (CMP) microspheres. Cu(II)-CA anions are successfully imprinted with the molar ration of 1:1 by Cu-CA-SIP at initial pH 4.0. Nearly 100% removal rate can be achieved even at low Cu(II)-CA concentration (0.5 mmol/L), and the maximum Cu(II) uptake of Cu-CA-SIP reaches 1.38 mmol/g at 303 K. In Cu(II)/Fe(III)-CA, Cu(II)/Ni(II)-CA, Cu(II)/Zn(II)-CA and Cu(II)/Cd(II)-CA systems, the relative selectivity coefficients of Cu-CA-SIP for Cu(II)-CA are 9.66, 2.32, 1.40 and 44.55, respectively. Moreover, Cu-CA-SIP can be retrieved with negligible loss of adsorption capacity after six times of reuse. The Cu-CA-SIP column can effectively treat the actual electroplating wastewater within 114 BV, and can still reach 104 BV after three dynamic cycles. Therefore, an innovative imprinted material is designed for the first time on the basis of coordination-configuration recognition mechanism for the treatment of electroplating wastewater, providing a new insight in developing surface imprinted polymer in environmental remediation.

β-cyclodextrin and its derivatives: application in wastewater treatment

Water is one of the basic necessities of life and having clean water is extremely important for human health. In recent years, β-cyclodextrin (β-CD)-based polymers and nanosystems have been extensively studied as adsorbents for the purpose of water purification. They present high efficiency and capability to remove inorganic, organic, and heavy metal impurities from wastewater as compared to conventional methods of water purification. β-CDs are cyclic polysaccharides having specific dimension of hydrophobic cavities and hydrophilic functional groups. The hydrophobic cavities form inclusion complexes through host-guest interactions. The hydroxyl groups form sites of hydrogen bonding and electrostatic interaction with pollutants. Additionally, they are also the sites of modification to bring about different derivatisation and polymerization reactions in order to impart desirable properties for efficient adsorption material. This article comprises of various derivatives of β-cyclodextrins: their nanoparticulate systems and their characterization and applications to remove different types of impurities from wastewater. The chemical reactions for their synthesis and mechanism of adsorption are highlighted.

Immobilization of Cu (II) via a graphene oxide-supported strategy for antibacterial reutilization with long-term efficacy

The past several decades have witnessed tremendous research to discover ways for controlling heavy metal pollution, but most of the strategies do not involve reuse of the captured heavy metals. Herein, we propose a graphene oxide -based strategy for the effective removal of Cu²⁺ ions from water, coupled with their reuse as an antibacterial agent. Using GO nanosheets as an adsorbent and nanosupport, the Cu²⁺ ions were effectively extracted from water (>99.9%) and reduced in situ to copper nanoparticles (Cu NPs) containing both crystalline Cu and Cu₂O. The as-captured Cu NPs showed efficient in vitro antibacterial ability against Escherichia coli, reducing the bacteria from 10⁹ to 10¹ CFU mL^-1 by using ¹ mg mL^-1 Cu NPs/GO NSs for 1 h. The minimum inhibitory concentration determined to be only 16 μg mL^-1. For practical applications, Cu recovered from wastewater could reduce bacteria by 8 log CFU in 1 h. The recovered Cu was still able to reduce the bacteria by 7 log CFU after 2 months of storage in an argon atmosphere. This strategy of extracting heavy metals and subsequently reutilizing to kill bacteria will be of great significance for environmental remediation and public healthcare.

Preparation of a double-network hydrogel based on wastepaper and its application in the treatment of wastewater containing copper(ii) and methylene blue

To reclaim and utilize wastepaper (WP), a WP/acrylamide double-network hydrogel (WP/PAM) was prepared to transform WP into efficient adsorbent for heavy metals and dye wastewater treatment. The structure and properties of the WP/PAM were characterized systematically by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), swelling performance (SR), Fourier transform infrared spectrum (FTIR), and X-ray photoelectron spectroscopy (XPS). Batch experiments showed that the adsorption process of Cu(ii) and MB followed the pseudo-second-order kinetic model and the Langmuir model. The maximum adsorption capacities of the WP/PAM for Cu(ii) and MB were 142.2 mg g⁻¹ and 1714.5 mg g⁻¹, respectively. The adsorption mechanism of Cu(ii) on the WP/PAM was related to ion exchange and complexation, while MB adsorption was driven by hydrogen bonding and electrostatic interaction. Besides, the WP/PAM performed well in treating simulated wastewater. The regeneration test indicated that the WP/PAM could be successfully reused after 6 cycles. This work provided an alternative choice for the recycling of WP and produced a potential adsorbent for the dye and heavy metals wastewater treatment.

In this research, wastepaper was innovatively compounded with acrylamide to prepare a wastepaper/acrylamide double-network hydrogel and was applied to the treatment of the mixed wastewater containing copper(ii) and methylene blue.

Investigation of mercury(II) and copper(II) sorption in single and binary systems by alginate/polyethylenimine membranes

This study investigates Hg(II) and Cu(II) sorption in single and binary systems by alginate/polyethylenimine membranes. Batch experiments are conducted to assess the metal sorption performance. FTIR and SEM-EDX analyses are used to identify metal binding mechanism. The sorption kinetics are better fitted by the pseudo-second-order-equation compared to the pseudo-first-order-equation. Three isotherms are compared for fitting the sorption in mono-component solutions and the Sips model gives the best simulation of experimental data. The competitive-Sips model fits well sorption data in Hg-Cu binary solutions and finds that the Cu uptake is drastically reduced by Hg competition. Copper(II) uptake remains negligible at low pH whereas it increases with pH up to 6 because of material deprotonation. Mercury(II) sorption behaves differently, it slightly changes from pH 1 (q_eq: 0.76 mmol g^-1) to pH 6 (q_eq: 0.84 mmol g^-1) due to chloro-anion formation. Therefore, playing with the pH allows separating Hg(II) from Cu(II).

Ninhydrin-functionalized chitosan for selective removal of Pb(II) ions: Characterization and adsorption performance

A chitosan-based adsorbents (CS-Ninhydrin) was prepared by grafting ninhydrin for Pb(II) ions adsorption. SEM-EDS, XRD and FTIR analysis were used to characterize the synthesized CS-Ninhydrin. The static adsorption experiments showed that CS-Ninhydrin had a good removal rate for Pb(II) ions in a wide range of pH 3 to 7, quickly reached equilibrium (120 min) and had a higher adsorption capacity (196 mg/g). Pseudo second-order and Langmuir models showed that the adsorption process of Pb(II) by CS-Ninhydrin was a single-layer chemical adsorption. Temperature experiments showed that the reaction was a spontaneous exothermic process. In the wastewater experiment, CS-Ninhydrin showed an excellent selectivity to Pb(II) ions. The reusability of CS-Ninhydrin was perfect after five adsorption-desorption cycles. The main adsorption mechanism was the chelating and electrostatic action between N and O groups in CS-Ninhydrin and Pb(II) ions. Therefore, the new adsorbent CS-Ninhydrin was expected to promote the wide application of chitosan in Pb(II) adsorption.

Preparation of a new magnetic ion-imprinted polymer and optimization using Box-Behnken design for selective removal and determination of Cu(II) in food and wastewater samples

A new magnetic Cu(II) IIP (Fe₃O₄@IIP-IDC) is synthesized by polymerization of Imidazole-4,5-dicarboxylic acid functionalized Allyl chloride, and significant improvement of its performance has been compared. SPE parameters were optimized using Box-Behnken design to achieve the twin objectives of quantitative determination and removal of Cu(II). FLPSO kinetic model and BS isotherm model fits well with the capacity of 175 mg g^-1. Analytical figures of merit includes a linearity range of 10-5,000 µg L^-1 (R² = 0.9986), preconcentration factor of 50 after eluting with 5 mL of 1 M HNO₃, LOD of 1.03 µg L^-1 and LOQ of 4.5 µg L^-1. Accuracy was assessed by analysis of SRM (Standard Reference Material) and recovery experiments after spiking in food samples (Tea, coffee, chocolate, spinach, infant milk substitute) and battery wastewater. Ease of use, reusability (15 cycles), rapid adsorption and high selectivity makes it a promising candidate for efficient and selective removal and trace determination.

Porous biochar modified with polyethyleneimine (PEI) for effective enrichment of U(VI) in aqueous solution

This study investigated the modification of moso bamboo biochar with polyethyleneimine (PEI) for the efficient enrichment of U(VI) in aqueous solution. The alkali/acid treated biochars with amine groups (PEI-alkali-biochar or PEI-acid-biochar) were characterized by SEM, BET, TGA, FTIR and XPS. The effects of contact time, U(VI) concentration, pH and ionic strength on U(VI) adsorption by PEI-alkali/acid-biochar were studied. U(VI) adsorption process on PEI-alkali/acid-biochar obeys pseudo-second-order model. Intraparticle diffusion model was used to investigate the controlled factors of the adsorption process. The fitting of Langmuir model gives the maximum adsorption capacities of 212.7 mg/g for PEI-alkali-biochar and 185.6 mg/g for PEI-acid-biochar, which are almost 9-10 times higher than that of pristine biochar (20.1 mg/g). The thermodynamic parameters illustrate that U(VI) adsorption on PEI-alkali/acid-biochar is an exothermic and spontaneous process. The FTIR and XPS analyses imply that U(VI) adsorption by PEI-alkali/acid-biochar is mainly controlled by complexation between U(VI) and amine groups. PEI-alkali/acid-biochar could be considered as a low-cost and outstanding material for U(VI) removal from radionuclide wastewater in practical application.

Effect of Hybrid mono/bimetallic Nanocomposites for an enhancement of Catalytic and Antimicrobial Activities

Exploring the new catalytic systems for the reduction of organic and inorganic pollutants from an indispensable process in chemical, petrochemical, pharmaceutical and food industries, etc. Hence, in the present work, authors motivated to synthesize bare reduced graphene oxide (rGO), polyaniline (PANI), three different ratios of rGO-PANI_{(80:20,50:50, 10:90)} composites and rGO-PANI_{(80:20,50:50, 10:90)} supported mono (Pd) & bimetallic [Pd: Au_{(1:1,1:2, 2:1)}] nanocomposite by a facile chemical reduction method. Also, it investigated their catalytic performances for the reduction of organic/inorganic pollutants and antimicrobial activities. All the freshly prepared bare rGO, PANI, three different ratios of rGO-PANI_{(80:20, 50:50,10:90)} composites and rGO-PANI_{(80:20, 50:50,10:90)}/Pd & Pd: Au_{(1:1, 1:2,2:1)} nanocomposite hybrid catalysts were characterized using UV-Vis, FT-IR, SEM, FE-SEM, EDAX, HR-TEM, XRD, XPS and Raman spectroscopy analysis. Among them, an optimized best composition of rGO-PANI_(80:20)/Pd: Au_(1:1) bimetallic nanocomposite hybrid catalyst exhibits better catalytic reduction and antimicrobial activities than other composites, as a result of strong electrostatic interactions between rGO, PANI and bimetal (Pd: Au) NPs through a synergistic effect. Hence, an optimized rGO-PANI_(80:20)/Pd:Au_(1:1) bimetallic nanocomposite catalyst would be considered as a suitable catalyst for the reduction of different nitroarenes, organic dyes, heavy metal ions and also significantly inhibit the growth of S. aureus, S. Typhi as well as Candida albicans and Candida kruesi in wastewater.

Highly efficient removal of Cu(ii) by novel dendritic polyamine–pyridine-grafted chitosan beads from complicated salty and acidic wastewaters

In this study, dendritic polyamine chitosan beads with and without 2-aminomethyl pyridine were facilely prepared and characterized. Compared to CN (without the pyridine function), more adsorption active sites, larger pores, higher nitrogen content, higher specific surface area, and higher strength could be obtained for CNP (with the pyridine function). CNP microspheres afforded a larger adsorption capacity than those obtained by CN for different pH values; further, the uptake amounts of Cu(ii) were 0.84 and 1.12 mmol g⁻¹ for CN and CNP beads, respectively, at pH 5. The CNP microspheres could scavenge Cu(ii) from highly acidic and salty solutions: the maximum simulated uptake amount of 1.93 mmol g⁻¹ at pH 5 could be achieved. Due to the strong bonding ability and weakly basic property of pyridine groups, the adsorption capacity of Cu(ii) at pH 1 was 0.75 mmol g⁻¹ in highly salty solutions, which was comparative to those obtained from the commercial pyridine chelating resin M4195 (Q_Cu(II) = 0.78 mmol g⁻¹ at pH 1). In addition, a distinct salt-promotion effect could be observed for CNP beads at both pH 5 and 1. Therefore, the prepared adsorbent CNP beads can have promising potential applications in the selective capturing of heavy metals in complex solutions with higher concentrations of H⁺ and inorganic salts, such as wastewaters from electroplating liquid and battery industries.

Dendritic polyamine chitosan (CNP) beads containing 2-aminomethyl pyridine were facilely prepared for the efficient removal of Cu(ii) ions from highly acidic and salty solutions.

Efficient removal of Alizarin Red S from aqueous solution by polyethyleneimine functionalized magnetic carbon nanotubes

Alizarin Red S (ARS) has been extensively used in the dyeing industry. In order to effectively remove the ARS form dyeing wastewater, polyethyleneimine (PEI)-functionalized magnetic carbon nanotubes (PEI@MCNTs) adsorbent was successfully prepared and its adsorption performances were also investigated in detail. The PEI@MCNTs could efficiently remove the ARS from acidic aqueous solution (pH ≤ 6.0) within 40 min under room temperature. Benefiting from a large number of adsorption sites and multiple interactions, PEI@MCNTs possessed high selectivity towards ARS with spontaneous adsorption process. The maximum adsorption capacity of PEI@MCNTs for ARS was 196.08 mg g^-1 obtained from Langmuir isotherm, higher than that of available conventional adsorbents. Moreover, the PEI@MCNTs could be easily collected by an external magnet, and then effectively regenerated through 10 mM NaOH solution. The prepared PEI@MCNTs could be considered as the promising adsorbent for the removal of anthraquinone dyes in large-scale wastewater treatment.

Micro- and Mesoporous Carbons Derived from KOH Activations of Polycyanurates with High Adsorptions for CO2 and Iodine

The adsorption ability of porous carbons toward contaminants is closely related to the porous structures and the working functional groups. In this aspect, two porous carbons, with the potential use as adsorbents for CO2 and iodine, were prepared from polycyclotrimerizations (PCTs) of flexible bisphenyl A dicyanate (BPAC) and rigid binaphthalenyl dicyanate (BNC) cyanate ester monomers. Primarily, PCT reactions of BPAC and BNC generated the respective nonporous c-BPAC and c-BNC precursors, which contain high amounts of nitrogen and oxygen heteroatoms. Further KOH activations of c-BPAC and c-BNC produced the respective porous a-BPAC and a-BNC carbons, which mainly contain oxygen heteroatoms. The a-BNC derived from rigid BNC contains both micro- and mesopores and is high in adsorbing both CO2 (6.3 mmol/g) and iodine; in contrast, the microporous a-BPAC is lower in adsorbing CO2 (3.9 mmol/g) and iodine. The effects of molecular flexibility of the starting cyanate ester on the micro- and mesopore distribution as well as the CO2 and iodine adsorption behaviors of the porous carbons are therefore probed in this study.

Preparation of PVDF/Hyperbranched-Nano-Palygorskite Composite Membrane for Efficient Removal of Heavy Metal Ions

In this work, three kinds of hyperbranched polyamidoamine-palygorskite (PAMAM-Pal) were designed and synthesized by grafting the first generation polyamidoamine (G1.0 PAMAM), G2.0 PAMAM and G3.0 PAMAM onto Pal surfaces, respectively. Then, these PAMAM-Pals were used as additives to prepare polyvinylidene fluoride (PVDF)/hyperbranched polyamidoamine-palygorskite bicomponent composite membranes. The structures of the composite membranes were characterized by Fourier transform infrared spectroscopy (FTIR), thermo gravimetric analysis (TEM), X-ray photoelectron spectroscopy (XPS), field-emission scanning electronmicroscopy (SEM), atomic force microscope (AFM) and Thermogravimetric analysis (TGA). The adsorption properties of composite membranes to heavy metal ions was studied, and the results found that the maximum adsorption capacities for Cu(II), Ni(II) and Cd(II) could reach 155.19 mg/g, 124.28 mg/g and 125.55 mg/g, respectively, for the PVDF/G3.0 PAMAM-Pal membrane, while only 23.70 mg/g, 17.74 mg/g and 14.87 mg/g could be obtained for unmodified membranes in the same conditions. The high adsorption capacity can be ascribed to the large number of amine-terminated groups, amide groups and carbonyl groups of the composite membrane. The above results indicated that the prepared composite membrane has a high adsorption capacity for heavy metal ions removal in water treatment.

Biogenic Synthesis of Silver Nanoparticle from Mushroom Exopolysaccharides and its Potentials in Water Purification

Objective:

This study reports a novel eco-friendly biosynthesis of Silver Nanoparticles (AgNPs) from Exopolysaccharides (EPS) ofLentinus edodesafter an attempt to optimise the production of EPS through mutagenesis. It further describes some potential application of silver nanoparticles in water treatment.

Methods:

A wild strain ofL. edodeswas subjected to UV irradiation, a physical mutagen, at 254 nm. The wild and resultant irradiated strains were then assessed for the production of EPS and subsequent application of the crude EPSs for biosynthesis of AgNPs. The particles were characterised by colour pattern and UV-visible spectroscopy. Based on superior EPS production and nanoparticle attributes, nanoparticles obtained from UV irradiated process were further subjected to Scanning Electron Microscopy (SEM). EPS produced was quantified by the phenol-sulphuric acid method and studied by GC-MS.

Results:

Results obtained for EPS productivity indicated the presence of monomer sugars such as arabinose (50.65%), mannose (19.20%), mannitol (15.58%), fructose (7.96%), trehalose (6.49%), and glucuronic acid, xylose, galactose and glucose with low percentages of ≤ 0.11. EPS productivity of wild and mutant strains was obtained as 1.044 and 2.783 mg/ml, respectively, after 7 days of fermentation. The result of EPS production for UV irradiated strain corresponds to a yield improvement of 2.7 fold of the wild-type. UV Spectroscopy and SEM analysis studies on EPS nanoparticle product of the improved (UV irradiated) strain indicated the formation of AgNPs at the absorption band of 421 nm with a size range of 50-100 nm.

Conclusion:

This study, which aimed at eco-friendly synthesis of myco-nanoparticle has established the novel ability ofL. edodes’polysaccharide in silver nanoparticles biosynthesis. It expounded potential frontiers of silver nanoparticles application in the water industry. To the best of the authors’ knowledge, this result represents the first report on the biosynthesis of AgNPs usingL. edode’sEPS.

Equilibrium and Kinetic Study of Lead and Copper Ion Adsorption on Chitosan-Grafted-Polyacrylic Acid Synthesized by Surface Initiated Atomic Transfer Polymerization

In this work, we synthesized chitosan grafted-polyacrylic acid (CS-g-PA) through surface-initiated atom transfer radical polymerization (SI-ATRP). We also studied the adsorption process of copper and lead ions onto the CS-g-PA surface. Adsorption equilibrium studies indicated that pH 4.0 was the best pH for the adsorption process and the maximum adsorption capacity over CS-g-PA for Pb²⁺ ions was 98 mg·g⁻¹ and for Cu²⁺ it was 164 mg·g⁻¹, while for chitosan alone (CS), the Pb²⁺ adsorption capacity was only 14.8 mg·g⁻¹ and for Cu²⁺ it was 140 mg·g⁻¹. Furthermore, the adsorption studies indicated that Langmuir model describes all the experimental data and besides, pseudo-second-order model was suitable to describe kinetic results for the adsorption process, demonstrating a larger kinetic constant of the process was larger for Pb²⁺ than Cu²⁺. Compared to other adsorbents reported, CS-g-PA had comparable or even superior adsorbent capacity and besides, all these results suggest that the new CS-g-PA polymers had potential as an adsorbent for hazardous and toxic metal ions produced by different industries.

Removal of Heavy Metals and Metalloids by Amino-Modified Biochar Supporting Nanoscale Zero-Valent Iron

Nanoscale zero-valent iron (nZVI), an environmentally benign material, has been used to remove heavy metals and metalloids from the aqueous phase because of its high reactivity and abundant reactive sites. To improve the stability of nZVI, nanoscale zero-valent iron supported by amino-modified biochar (ZVIA-BC) was prepared and characterized. Its ability to remove heavy metals and metalloid was investigated. Fourier transform infrared spectroscopy analyses showed that the amino group was chemically bound to the functional groups of biochar. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction revealed that zero-valent iron was loaded on the biochar surface. High-resolution transmission electron microscope images showed that the particle size of iron was ∼50 nm and the particles consisted of roughly spherical cores covered with a shell that was uniformly 2- to 3-nm thick. Furthermore, measuring the zeta potentials at various pH values indicated that the iso-electric points occurred within the pH range of 7.50 to 7.56. Additionally, heavy metals and metalloids, including Cd(II), Ni(II), Cu(II), Cr(VI) and As(V) adsorption isotherms, on ZVIA-BC were significantly nonlinear, and ZVIA-BC exhibited a superior ability to remove these heavy metals and metalloids, especially for Cr(VI) and As(V). Characterization with high-resolution XPS revealed that reduction of heavy metals and metalloids occurred on the surface of ZVIA-BC. The main mechanisms for removal were reduction, complexation, co-precipitation, and electrostatic interaction.

High-performance Cu2+ adsorption of birnessite using electrochemically controlled redox reactions

Manganese oxides are proposed as superior adsorbents for heavy metal ions, and their adsorption capacities can be greatly improved by electrochemical methods. In this work, birnessite was used as electrode material for Cu²⁺ adsorption by multi-cycle electrochemical redox reaction. The effects of solution pH and potential window on Cu²⁺ electrosorption capacity were further investigated. The results showed that the electrosorption capacity for Cu²⁺ reached as high as 372.3 mg g^-1 by electrochemical redox, which was remarkably larger than the adsorption isotherm capacity (44.3 mg g^-1). In addition, birnessite could be reused for many times after electrochemical activation. In the process of electrosorption, the amount of copper electrodeposited on the counter electrode accounted for less than 3.2% of the total removal capacity. The enhancement of Cu²⁺ adsorption capacity could be attributed to the changes in the chemical composition and the dissolution-recrystallization processes of birnessite during the electrochemical redox reactions. The electrosorption capacity increased with increasing pH from 3.0 to 5.0 and potential window width. The present work shows that controllable redox reaction of birnessite is a promising method for the removal of Cu²⁺ from wastewater.