Design and synthesis of core-shell Fe3O4@PTMT composite magnetic microspheres for adsorption of heavy metals from high salinity wastewater

Calcium-doped magnetic humic acid nano particles for the efficient removal of heavy metals from wastewater: the role of Ca

Ca doping is an effective method for improving the adsorption capacity of HA-Fe aggregates and regulating their structures. Understanding the structural characteristics of Ca-HA-Fe aggregates can help explore their microscopic adsorption effect on heavy metals. However, the heterogeneity of HA results in an incomplete understanding of the structural characteristics of the ternary system of Ca-HA-Fe aggregates and adsorption of the quaternary system of Ca-HA-Fe-Pb/Cu/Cd. In this study, interactions between Ca-HA-Fe ternary and Ca-HA-Fe-Pb/Cu/Cd quaternary systems were discussed from a molecular perspective. The structures of the basic structural units of HA were identified. Density functional theory (DFT) was employed to calculate the stable states of basic structural units of HA and Ca2+. The results showed that hydroxyl and carboxyl groups exhibited the highest capacity to bind with Ca2+. The interactions among Ca, HA, and Fe led to the formation of network aggregates. The binding energies of functional groups for heavy metals and the feasibility of ion exchange were calculated by the method of experiment and DFT. According to the contribution of functional group complexation and ion exchange, the ion exchange values for Pb2+, Cu2+, and Cd2+ were 66.71%, 62.87%, and 60.79%, respectively, which indicated that Ca2+ ion exchange showed considerable potential in enhancing the adsorption capacity of heavy metals.

Mesoporous Magnetic/Polymer Hybrid Nanoabsorbent for Rapid and Efficient Removal of Heavy Metal Ions from Wastewater

As an advanced water purification technology, magnetic nanoabsorbents are highly attractive for their sustainability, robustness, and energy efficiency. However, magnetic responsiveness and high adsorptive capacity are irreconcilable during the design and synthesis of a high-performance magnetic nanoabsorbent. Here, we address this issue by designing a kind of mesoporous magnetic polymer hybrid microspheres, where functional polymers such as polyrhodanine and polypyrrole were attached to the pore walls in the interior of mesoporous Fe3O4 microspheres through in situ polymerization. Due to the integrated large saturation magnetic moment, porous structure, and dense polymer layer, the mesoporous magnetic polymer hybrid microspheres demonstrated fast magnetic responsiveness, excellent recycling performance, and high adsorption capacities toward Pb(II) ions (189 mg g-1) for polyrhodanine and Cr(VI) ions (199 mg g-1) for polypyrrole. Furthermore, their potential application in wastewater treatment was verified by a self-made magnetic separation column, where the designed magnetic nanoabsorbent exhibits significant advantages including rapid separation of heavy metal ions and high outflow. This study provided a promising magnetic polymer hybrid nanoabsorbent for realizing efficient removal of heavy metal ions from wastewater.

One-Pot Synthesis of Affordable Redox-Responsive Drug Delivery System Based on Trithiocyanuric Acid Nanoparticles

Redox-responsive drug delivery systems present a promising avenue for drug delivery due to their ability to leverage the unique redox environment within tumor cells. In this work, we describe a facile and cost-effective one-pot synthesis method for a redox-responsive delivery system based on novel trithiocyanuric acid (TTCA) nanoparticles (NPs). We conduct a thorough investigation of the impact of various synthesis parameters on the morphology, stability, and loading capacity of these NPs. The great drug delivery potential of the system is further demonstrated in vitro and in vivo by using doxorubicin as a model drug. The developed TTCA-PEG NPs show great drug delivery efficiency with minimal toxicity on their own both in vivo and in vitro. The simplicity of this synthesis, along with the promising characteristics of TTCA-PEG NPs, paves the way for new opportunities in the further development of redox-responsive drug delivery systems based on TTCA.

Bioinorganic Nanoparticles for the Remediation of Environmental Pollution: Critical Appraisal and Potential Avenues

Nowadays, environmental pollution has become a critical issue for both developed and developing countries. Because of excessive industrialization, burning of fossil fuels, mining and exploration, extensive agricultural activities, and plastics, the environment is being contaminated rapidly through soil, air, and water. There are a variety of approaches for treating environmental toxins, but each has its own set of restrictions. As a result, various therapies are accessible, and approaches that are effective, long-lasting, less harmful, and have a superior outcome are extensively demanded. Modern research advances focus more on polymer-based nanoparticles, which are frequently used in drug design, drug delivery systems, environmental remediation, power storage, transformations, and other fields. Bioinorganic nanomaterials could be a better candidate to control contaminants in the environment. In this article, we focused on their synthesis, characterization, photocatalytic process, and contributions to environmental remediation against numerous ecological hazards. In this review article, we also tried to explore their recent advancements and futuristic contributions to control and prevent various pollutants in the environment.

Characterization and Mechanistic Study of Heavy Metal Adsorption by Facile Synthesized Magnetic Xanthate-Modified Chitosan/Polyacrylic Acid Hydrogels

A simple method was used to synthesize magnetic xanthate-modified chitosan/polyacrylic acid hydrogels that were used to remove heavy metal ions from an aqueous solution. Xanthate modification of chitosan significantly improved adsorption performance: individual adsorption capacities of the hydrogel for Cu(II), Cd(II), Pb(II), and Co(II) ions were 206, 178, 168, and 140 mg g^-1, respectively. The magnetic hydrogels had good regeneration ability and were effectively separated from the solution by use of a magnet. Adsorption kinetic data showed that the removal mechanism of heavy metal ions from the solution by magnetic hydrogels occurs mainly by chemical adsorption. The equilibrium adsorption isotherms were well-described by the Freundlich and Langmuir equations. Positive values were found for the Gibbs standard free energy and enthalpy, indicating an increase in the disorder at the solid-liquid interface during adsorption. Magnetic xanthate-modified chitosan-based hydrogels that exhibit high adsorption efficiency, regeneration, and easy separation from a solution have broad development prospects in various industrial sewage and wastewater treatment fields.

Water-based Fe3O4 magnetic fluid-coated Aspergillus niger spores for treating liquid contaminated with Cr(VI)

The use of magnetic biosorbents for the remediation of heavy metals has attracted increasing attention due to their ease of separation and reusability. We developed a method for preparing superparamagnetic biosorbent materials using water-based magnetic fluids. Water-based magnetic fluid-spores (WMFSs) were obtained by combining water-based magnetic fluid (WMF) with Aspergillus niger spores at ratios of 0.6:1 (WMFS1), 0.8:1 (WMFS2), 1:1 (WMFS3), 1.2:1 (WMFS4), and 1.4:1 (WMFS5). A magnetic composite material was prepared from magnetic nanoparticles and spores in a ratio of 1:1 as a control. The adsorption efficiency and separation effect of WMFS3 were significantly better than those of the magnetic composite material. The morphology and structure of WMFS3 were characterized by performing transmission electron microscopy. The results showed that Fe₃O₄ magnetic particles were uniformly coated on the spore surface. The superparamagnetism of WMFS3 was tested using a vibrating sample magnetometer. At pH 2.0, the maximum adsorption capacity of WMFS3 for Cr(VI) was 105 mg/g; in the pH range of 2.0-3.0, the adsorption equilibrium time of WMFS3 was 60 min. Thus, the adsorption process conformed to the pseudo-second-order kinetic model and Freundlich isotherm. Thermodynamic studies showed that the process was spontaneous and endothermic. The adsorption mechanisms of WMF3 for Cr(VI) included electrostatic, reduction, and complexation adsorption. This biosorbent material showed excellent adsorption performance for Cr(VI) and is promising for wastewater resource applications.

Recycling of Waste Toner Powder as Adsorbent to Remove Aqueous Heavy Metals

The removal of Cd²⁺, Zn²⁺ and Ni²⁺ from metal solutions onto waste toner power (WTP) was investigated. The influence of parameters such as pH, contact time, initial metal concentration and adsorbent dosage was studied in batch adsorption experiments. Batch equilibrium experiments showed that the highest removal efficiency for Zn²⁺ and Cd²⁺ occurs at pH 7, while pH 5 is the most suitable for Ni²⁺ removal. The amount of metal removed (mg/g) improved when increasing the initial concentration, and sorption of heavy metals reached equilibrium in 24 h. Metals’ uptake increased with increasing adsorbent dosage. The adsorption isotherms of Zn²⁺, Cd²⁺ and Ni²⁺ onto WTP fit the Langmuir better than the Freundlich model with correlation coefficient R² values ranging from 0.998 to 0.968 and 0.989 to 0.881, respectively. The data showed that the maximum adsorption capacity of heavy metals, a_max, ranged from 2.42 to 1.61 mg/g, from 6.22 to 2.01 mg/g and from 3.49 to 2.56 mg/g for Ni²⁺, Zn²⁺ and Cd²⁺, respectively, with the three WTPs used in this study. This adsorbent can potentially be used to remove metal ions from wastewater.

Recent advances in nanoremediation: Carving sustainable solution to clean-up polluted agriculture soils

Agriculture is one of the foremost significant human activities, which symbolizes the key source for food, fuel and fibers. This activity results in a lot of ecological harms particularly with the excessive usage of chemical fertilizers and pesticides. Different agricultural practices have remained industrialized to advance food production, due to the growth in the world population and to meet the food demand through the routine use of more effective fertilizers and pesticides. Soil is intensely embellished by environmental contamination and it can be stated as "universal incline." Soil pollution usually occurs from sewage wastes, accidental discharges or as byproducts of chemical residues of unrestrained production of numerous materials. Soil pollution with hazardous materials alters the physical, chemical, and biological properties, causing undesirable changes in soil fertility and ecosystem. Engineered nanomaterials offer various solutions for remediation of contaminated soils. Engineered nanomaterial-enable technologies are able to prevent the uncontrolled release of harmful materials into the environment along with capabilities to combat soil and groundwater borne pollutants. Currently, nanobiotechnology signifies a hopeful attitude to advance agronomic production and remediate polluted soils. Studies have outlined the way of nanomaterial applications to restore the eminence of the environment and assist the detection of polluted sites, along with potential remedies. This review focuses on the latest developments in agricultural nanobiotechnology and the tools developed to combat soil or land and or terrestrial pollution, as well as the benefits of using these tools to increase soil fertility and reduce potential toxicity.

Synthesis and Characterization of a Magnetic Carbon Nanofiber Derived from Bacterial Cellulose for the Removal of Diclofenac from Water

Engineering and synthesis of novel materials are vital for removing emerging pollutants, such as pharmaceuticals from contaminated water. In this study, a magnetic carbon nanofiber (MCF) fabricated from bacterial cellulose was tested for the adsorption of diclofenac from water. The physical and chemical properties of the synthesized adsorbent were examined by field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, energy-dispersive X-ray spectroscopy (EDS), a vibrating sample magnetometer (VSM), Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The characterization results showed that the MCF is a carbon nanofiber with a three-dimensional interconnect network, forming a porous material (mesopores and macropores) with a specific surface area of 222.3 m²/g. The removal of diclofenac (10 mg/L) by the MCF (0.75 g/L) was efficient (93.2%) and fast (in 20 min). According to the Langmuir isotherm model fitting, the maximum adsorption capacity of the MCF was 43.56 mg/g. Moreover, continuous adsorption of diclofenac onto MCF was investigated in a fixed-bed column, and the maximum adsorption capacity was found to be 67 mg/g. The finding of this research revealed that the MCF could be a promising adsorbent used to remove diclofenac from water, while it can be easily recovered by magnetic separation.

Technology status and trends of industrial wastewater treatment: A patent analysis

Globally, 80% of wastewater, among which 28% came from industry, returned to the ecosystem without treatment or reuse. The discharge of industrial wastewater poses public health and environmental concerns. The necessity and urgency of industrial wastewater treatment (IWT) will bring great challenges to most countries. This paper conducted the patent analysis combined with text mining to quantitatively analyze 11,840 patents related to IWT in the Derwent Innovations Index database. The results showed that: From 1973 to 2020, the number of patents related to IWT annually was increasing consistently. China ranked first in the number of patent publications. In contrast, the United States and some patent organizations, such as World Intellectual Property Organization, produced fewer patents, while they played more important roles in knowledge transfer. The core technology analysis suggested that method, device, material and related industry were hot topics. From activated sludge treatment technology, industrial wastewater treatment technology had gone through a development process from single technology treatment to combined technologies treatment. In the foreseeable future, research on devices for physical treatment, advanced oxidation processes, automated and energy-saving treatment systems were the promising directions.

Simultaneous decontamination of multi-pollutants: A promising approach for water remediation

Water remediation techniques have been extensively investigated due to the increasing threats of soluble pollutants posed on the human health, ecology and sustainability. Confronted with the complex composition matrix of wastewater, the simultaneous elimination of coexisting multi-pollutants remains a great challenge due to their different physicochemical properties. By integrating multi-contaminants elimination processes into one unit operation, simultaneous decontamination attracted more and more attention under the consideration of versatile applications and economical benefits. In this review, the state-of-art simultaneous decontamination methods were systematically summarized as chemical precipitation, adsorption, photocatalysis, oxidation-reduction, biological removal and membrane filtration. Their applications, mechanisms, mutual interactions, sustainability and recyclability were outlined and discussed in detail. Finally, the prospects and opportunities for future research were proposed for further development of simultaneous decontamination. This work could provide guidelines for the design and fabrication of well-organized simultaneous decontaminating system.

Synthesis of Fe3O4@mZrO2-Re (Re = Y/La/Ce) by Using Uniform Design, Surface Response Methodology, and Orthogonal Design & Its Application for As3+ and As5+ Removal

In this study, iron oxide (Fe₃O₄) was coated with ZrO₂, and doped with three rare earth elements((Y/La/Ce), and a multi-staged rare earth doped zirconia adsorbent was prepared by using uniform design U₁₄, Response Surface methodology, and orthogonal design, to remove As³⁺ and As⁵⁺ from the aqueous solution. Based on the results of TEM, EDS, XRD, FTIR, and N₂-adsorption desorption test, the best molar ratio of Fe₃O₄:TMAOH:Zirconium butoxide:Y:La:Ce was selected as 1:12:11:1:0.02:0.08. The specific surface area and porosity was 263 m²/g, and 0.156 cm³/g, respectively. The isothermal curves and fitting equation parameters show that Langmuir model, and Redlich Peterson model fitted well. As per calculations of the Langmuir model, the highest adsorption capacities for As³⁺ and As⁵⁺ ions were recorded as 68.33 mg/g, 84.23 mg/g, respectively. The fitting curves and equations of the kinetic models favors the quasi second order kinetic model. Material regeneration was very effective, and even in the last cycle the regeneration capacities of both As³⁺ and As⁵⁺ were 75.15%, and 77.59%, respectively. Adsorption and regeneration results suggest that adsorbent has easy synthesis method, and reusable, so it can be used as a potential adsorbent for the removal of arsenic from aqueous solution.

Investigation of organic impurity and its occurrence in industrial waste salt produced by physicochemical process

Industrial waste salt is classified as hazardous waste to the environment. The organic impurity and its occurrence in industrial waste salt affect the salt resource utilization. In this paper, composition quantitative analysis, XRD, TG-DSC, SEM/FIB-SEM coupled with EDS, FTIR, XPS and GC-Ms were chosen to investigate the organic impurity and its occurrence in industrial waste salt. The organic impurities owe small proportion (1.77%) in the specimen and exhibit weak thermal stability within the temperature of 600°C. A clear definition of organic impurity, including 11 kinds of organic compounds, including aldehyde, benzene and its derivatives etc., were detected in the industrial waste salt. These organic impurities, owing (C-O/C-O-C, C-OH/C = O, C–C/CH_x/C = C etc.)-containing function group substance, are mainly distributed both on the surface and inside of the salt particles. Meanwhile, the organic substance may combine with metal cations (Ni²⁺, Mg²⁺, Cu²⁺ etc.) through functional groups, such as hydroxide, carbonyl etc., which increases its stability in the industrial waste salt. These findings provide comprehensive information for the resource utilization of industrial waste salt from chemical industry etc.

Synthesis of magnetic core-shell amino adsorbent by using uniform design and response surface analysis (RSM) and its application for the removal of Cu2+, Zn2+, and Pb2

The magnetic Fe₃O₄ was synthesized by using a one-step solvothermal method. Then, anhydrous ethanol as a solvent, tetramethyl ammonium hydroxide (TMAOH) as an auxiliary agent, tetraethyl orthosilicate (TEOS) as a silicon source, and (3-aminopropyl) triethoxysilane (APTES) as amino source were used to prepare Fe₃O₄@mSiO₂-NH₂ by using the sol-gel method. Uniform design U14*(14⁵) and the response surface method (RSM) were used to optimize the synthesis ratio. According to the results of TEM, SEM, N₂ adsorption-desorption test, VSM, and XRD, it found that the best coating effect obtained when the relative molar ratio of TMAOH:TEOS:APTES:Fe₃O₄ was 5:4:6:0.45. The results of EDS and elemental analysis confirmed the success of amino group coating; VSM magnetization after surface modification was 32 emu/g; BET results show that specific surface area is 236 m²/g, size 5 nm, and the pore volume is 0.126 cm³/g. The removal of Cu²⁺, Zn²⁺, and Pb²⁺ by Fe₃O₄@mSiO₂-NH₂ was studied at the optimal initial pH value 6 of the adsorption test system. The isothermal adsorption results show that the Langmuir model and Redlich-Peterson model are more suitable than the Freundlich model to describe the adsorption behavior, and Cu²⁺, Zn²⁺, and Pb²⁺ adsorption is mainly single molecular layer. The maximum adsorption capacity qm of the Langmuir model for Cu²⁺, Zn²⁺, and Pb²⁺ removal was 48.04 mg/g, 41.31 mg/g, and 62.17 mg/g, respectively. The adsorption kinetic rates of Cu²⁺, Zn²⁺, and Pb²⁺ on Fe₃O₄@mSiO₂-NH₂ relatively more suitable for pseudo-second-order kinetic model, i.e., R², were ranged between 0.995 and 0.999, and the suitable reaction time was 60 min. These results proved that Fe₃O₄@m-SiO₂-NH₂ prepared by using this method is easy to synthesize, has easy recovery, is ecofriendly, and can be potential adsorbent for Cu²⁺, Zn²⁺, and Pb²⁺ removal.

Magnetically Recyclable Wool Keratin Modified Magnetite Powders for Efficient Removal of Cu2+ Ions from Aqueous Solutions

The treatment of wastewater containing heavy metals and the utilization of wool waste are very important for the sustainable development of textile mills. In this study, the wool keratin modified magnetite (Fe3O4) powders were fabricated by using wool waste via a co-precipitation technique for removal of Cu2+ ions from aqueous solutions. The morphology, chemical compositions, crystal structure, microstructure, magnetism properties, organic content, and specific surface area of as-fabricated powders were systematically characterized by various techniques including field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), thermogravimetric (TG) analysis, and Brunauer-Emmett-Teller (BET) surface area analyzer. The effects of experimental parameters such as the volume of wool keratin hydrolysate, the dosage of powder, the initial Cu2+ ion concentration, and the pH value of solution on the adsorption capacity of Cu2+ ions by the powders were examined. The experimental results indicated that the Cu2+ ion adsorption performance of the wool keratin modified Fe3O4 powders exhibited much better than that of the chitosan modified ones with a maximum Cu2+ adsorption capacity of 27.4 mg/g under favorable conditions (0.05 g powders; 50 mL of 40 mg/L CuSO4; pH 5; temperature 293 K). The high adsorption capacity towards Cu2+ ions on the wool keratin modified Fe3O4 powders was primarily because of the strong surface complexation of -COOH and -NH2 functional groups of wool keratins with Cu2+ ions. The Cu2+ ion adsorption process on the wool keratin modified Fe3O4 powders followed the Temkin adsorption isotherm model and the intraparticle diffusion and pseudo-second-order adsorption kinetic models. After Cu2+ ion removal, the wool keratin modified Fe3O4 powders were easily separated using a magnet from aqueous solution and efficiently regenerated using 0.5 M ethylene diamine tetraacetic acid (EDTA)-H2SO4 eluting. The wool keratin modified Fe3O4 powders possessed good regenerative performance after five cycles. This study provided a feasible way to utilize waste wool textiles for preparing magnetic biomass-based adsorbents for the removal of heavy metal ions from aqueous solutions.

Aerobic Oil-Phase Cyclic Magnetic Adsorption to Synthesize 1D Fe2O3@TiO2 Nanotube Composites for Enhanced Visible-Light Photocatalytic Degradation

In this work, Fe₂O₃@TiO₂ nanostructures with staggered band alignment were newly designed by an aerobic oil-phase cyclic magnetic adsorption method. XRD and TEM analyses were performed to verify the uniform deposition of Fe₂O₃ nanoparticles on the nanotube inner walls of TiO₂. The steady-state degradation experiments exhibited that 1FeTi possessed the most superior performance, which might be ascribable to the satisfying dark adsorption capacity, efficient photocatalytic activity, ease of magnetic separation, and economic efficiency. These results indicated that the deposition of Fe₂O₃ into TiO₂ nanotubes significantly enhanced the activity of Fe₂O₃, which was mainly ascribed to the Fe₂O₃-induced formation of staggered iron oxides@TiO₂ band alignment and thus efficient separation of h⁺ and e^-. Furthermore, the PL intensity and lifetime of the decay curve were considered as key criterions for the activity's evaluation. Finally, the leaching tests and regeneration experiments were also performed, which illustrated the inhibited photodissolution compared with TiO₂/Fe₃O₄ and stable cycling ability, enabling 1FeTi to be a promising magnetic material for photocatalytic water remediation.

Magnetic supramolecular polymer: Ultrahigh and highly selective Pb(II) capture from aqueous solution and battery wastewater

For the practical capture of heavy metal ions from wastewater, fabricating environmental friendly adsorbents with high stability and super adsorption capacity are pursuing issue. In this work, we develop magnetic supramolecular polymer composites (M-SMP) by using a simple two-step hydrothermal method. Systematical characterizations of morphological, chemical and magnetic properties were conducted to confirm the formation of M-SMP composites. The resulting M-SMP composites were applied to remove Pb(II) from aqueous solution and from real battery wastewater, and easy separation was achieved using a permanent magnet. By investigating the effects of various parameters, we optimized their operating condition for Pb(II) adsorption by the M-SMP. The uptake of Pb(II) onto M-SMP fitted well the pseudo-second-order and Langmuir isotherm models, and favourable thermodynamics showed a spontaneous endothermic process. The SMP endowed M-SMP with ultrahigh adsorption capacity for Pb(II) (946.9 mg g^-1 at pH = 4.0, T = 298 K), remarkable selectivity, satisfactory stability and desirable recyclability. In Pb-contaminated lead-acid battery industrial wastewater, the concentration of Pb(II) declined from 18.070 mg L^-1 to 0.091 mg L^-1, which meets the current emission standard for the battery industry. These merits, combined with simple synthesis and convenient separation, make M-SMP an outstanding scavenger for the elimination of industrial Pb(II) wastewater.

Partial Oxidation Strategy to Synthesize WS2/WO3 Heterostructure with Enhanced Adsorption Performance for Organic Dyes: Synthesis, Modelling, and Mechanism

In this work, a facile oxidation strategy was developed to prepare novel tungsten disulfide/tungsten trioxide (WS₂/WO₃) heterostructures for adsorbing organic dyes efficiently by combining the hydrophilic property of WO₃ and the superior dye affinity of WS₂. The structural and elemental properties of the synthesized hybrid materials were systematically investigated, and the results demonstrated the retained flower-like morphology of the primitive WS₂ and the successful introduction of WO₃. Furthermore, surface properties such as a superior hydrophilicity and negative-charged potential were also demonstrated by a water contact angle characterization combined with a Zeta potential analysis. The performance of the obtained WS₂/WO₃ hybrid materials for removing Rhodamine B (RhB) from wastewater was evaluated. The results showed that the maximum adsorption capacity of the newly synthesized material could reach 237.1 mg/g. Besides, the adsorption isotherms were also simulated by a statistical physics monolayer model, which revealed the non-horizontal orientation of adsorbates and endothermic physical interaction. Finally, the adsorption mechanism and the recyclability revealed that the partial oxidation strategy could contribute to a higher adsorption capacity by modulating the surface properties and could be applied as a highly efficient strategy to design other transition metal dichalcogenides (TMDs) heterostructures for removing organic dyes from wastewater.

Removal of heavy metals in aquatic environment by graphene oxide composites: a review

As the most important graphene derivate, graphene oxide (GO) is a high-efficient adsorbent for the removal of heavy metals in aquatic environment due to its abundant oxygen functional groups, enormous specific area, and strong hydrophilia. However, there are some drawbacks, such as easily aggregating and difficult separation, restricting the environmental application of GO. GO is not a suitable adsorbent by itself. Hence, some materials were used to synthesize GO composites, and GO composites are commonly characterized by high adsorption capacity to overcome the above drawbacks. This review discusses five main GO composites-GO-chitosan, GO-alginate, GO-SiO₂, NZVI-rGO, and magnetic GO composites-and summarizes the synthesis methods of GO composites and its application for the removal of heavy metals in aquatic environments. The influencing factors, adsorption capacities, and mechanisms related to the removal of heavy metals by GO composites are highlighted. Lastly, the application potentials and challenges of GO composites for aqueous environmental remediation are discussed. Graphical abstract.

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.

Synthesis of Fe3O4@PVBC-TMT nanoparticles for the efficient removal of heavy metals ions

Core–shell magnetic Fe₃O₄@PVBC–TMT (Fe₃O₄@polyvinylbenzyl chloride–trithiocyanuric acid) nanoparticles containing trithiocyanuric acid groups were fabricated and employed for the fast removal of heavy metals from an aquatic environment. The morphology, structure and properties of Fe₃O₄@PVBC–TMT nanoparticles were characterized by a series of modern analytical tools. The adsorption behavior of the Fe₃O₄@PVBC–TMT nanoparticles for heavy metals ions in aqueous solutions was investigated by batch experiments. The maximum removal capacities of the Fe₃O₄@PVBC–TMT nanoparticles toward Mn²⁺, Ni²⁺, Cu²⁺, Cd²⁺ and Pb²⁺ ions were 127.4, 146.6, 180.5, 311.5, and 528.8 mg g⁻¹, respectively. Importantly, it is found that Pb²⁺ ions can be completely and quickly removed by the Fe₃O₄@PVBC–TMT nanoparticles. The equilibrium was established within 6 min, and the removal efficiencies were found to be 99.9%, 99.8% and 99.5% for Pb²⁺ ions at the initial concentrations of 100 mg L⁻¹, 200 mg L⁻¹ and 300 mg L⁻¹, respectively. It is hoped that the core–shell magnetic Fe₃O₄@PVBC–TMT nanoparticles may find application in wastewater treatment.

Core–shell Fe₃O₄@PVBC–TMT nanoparticles were fabricated and served as a valid magnetic adsorbent for the removal of heavy metals ions.

Synthesis, Characterization, Kinetics, and Thermodynamics of EDTA-Modified Chitosan-Carboxymethyl Cellulose as Cu(II) Ion Adsorbent

A new adsorbent derived from the naturally occurring biopolymers, chitosan (CS) and carboxymethyl cellulose (CMC) was prepared by cross-linking them using EDTA. EDTA having high affinity for metal ions can be used to enhance the chelation properties of the adsorbent enormously. The product obtained (chitosan-EDTA-CMC, CSECM) was characterized by different techniques: FTIR, XRD, SEM/EDAX, TGA, and XPS. The parameters for evaluation of the adsorption properties for removal of Cu(II) ions from the aqueous solution were determined using the batch adsorption method by studying the effect of pH, contact time, initial ion concentration, and temperature on adsorption. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetic models were applied to study the kinetics of the adsorption process, whereas Langmuir, Freundlich, Temkin, and D-R models were applied to evaluate the thermodynamics of the adsorption process. The kinetic adsorption parameters were in best agreement with the pseudo-second-order model, while thermodynamic parameters best fitted to the Langmuir isotherm at different temperatures for adsorption of Cu(II) ions from aqueous solution with a maximum adsorption capacity of 142.95 mg/g at pH 5.5. CSECM showed excellent regeneration capability and recovery of the Cu(II) ion up to five cycles without the loss of the adsorption efficiency, which is the best characteristic to select the appropriate choice of the adsorbent. The adsorbent was also employed in batch experiments to evaluate the adsorption of hardness, producing common metal ions in single and real wastewater solutions.

Fate of environmental pollutants

This annual review covers the literature published in 2018 on topics related to the occurrence and fate of environmental pollutants in wastewater. Due to the vast amount of literature published on this topic, we have discussed only a portion of the quality research publications, due to the limitation of space. The abstract search was carried out using Web of Science, and the abstracts were selected based on their relevance. In a few cases, full-text articles were referred to understand new findings better. This review is divided into the following sections: antibiotic-resistant bacteria (ARBs) and antibiotic-resistant genes (ARGs), disinfection by-products (DBPs), drugs of abuse (DoAs), estrogens, heavy metals, microplastics, per- and polyfluoroalkyl compounds (PFAS), pesticides, and pharmaceuticals and personal care products (PPCPs), with the addition of two new classes of pollutants to previous years (DoAs and PFAS).

A novel and biocompatible Fe3O4 loaded chitosan polyelectrolyte nanoparticles for the removal of Cd2+ ion

In this work, Fe₃O₄ loaded chitosan (CS) nanoparticles (NPs) and microparticles (MPs) were synthesized based on ionic gelation technology for the removal of Cd²⁺ ion. The influencing parameters including initial concentration, pH, contact time and recycling was evaluated and optimized. The results showed that particle size of Fe₃O₄ loaded CS NPs and MPs was in the range of 164.05-768.69 nm, and the former showed relatively higher adsorption capacities (97.86 mg/g) on Cd²⁺ ion than the latter after 90 min at pH 5.0 for the solutions with initial Cd²⁺ ion of 100 mg/L, respectively. Brunauer, Emmett and Teller (BET) test illustrated 61.48 m²/g of specific surface area, 0.0274 cm³/g of pore volume and 6.03 nm average pore size. The results of FT-IR, TEM, EDS and XRD indicated that Fe₃O₄ was well incorporated into CS NPs and MPs. Moreover, the adsorption equilibrium data fitted well with Langmuir isotherm model and adsorption process followed the pseudo-second-order model. The adsorption mechanisms could be well explained though coordination and electrostatic attraction. Findings of this work highlighted the potential using Fe₃O₄ loaded CS NPs as an effective and recyclable adsorbent for the removal of heavy metal ions in industrial wastewater treatment.

The Roles of Nanomaterials in Conventional and Emerging Technologies for Heavy Metal Removal: A State-of-the-Art Review

Heavy metal (HM) pollution in waterways is a serious threat towards global water security, as high dosages of HM poisoning can significantly harm all living organisms. Researchers have developed promising methods to isolate, separate, or reduce these HMs from water bodies to overcome this. This includes techniques, such as adsorption, photocatalysis, and membrane removal. Nanomaterials play an integral role in all of these remediation techniques. Nanomaterials of different shapes have been atomically designed via various synthesis techniques, such as hydrothermal, wet chemical synthesis, and so on to develop unique nanomaterials with exceptional properties, including high surface area and porosity, modified surface charge, increment in active sites, enhanced photocatalytic efficiency, and improved HM removal selectivity. In this work, a comprehensive review on the role that nanomaterials play in removing HM from waterways. The unique characteristics of the nanomaterials, synthesis technique, and removal principles are presented. A detailed visualisation of HM removal performances and the mechanisms behind this improvement is also detailed. Finally, the future directions for the development of nanomaterials are highlighted.

Facile Synthesis of Polypyrrole-Functionalized CoFe₂O₄@SiO₂ for Removal for Hg(II)

In order to avoid using toxic or harmful operational conditions, shorten synthesis time, enhance adsorption capacity, and reduce operational cost, a novel magnetic nano-adsorbent of CoFe₂O₄@SiO₂ with core–shell structure was successfully functionalized with polypyrrole (Ppy). The physical and chemical properties of CoFe₂O₄@SiO₂-Ppy are examined by various means. The as-prepared CoFe₂O₄@SiO₂-Ppy nanomaterial was used to adsorb Hg²⁺ from water. During the process, some key effect factors were studied. The adsorption process of Hg²⁺ onto CoFe₂O₄@SiO₂-Ppy was consistent with the pseudo-second-order kinetic and Langmuir models. The Langmuir capacity reached 680.2 mg/g, exceeding those of many adsorbents. The as-prepared material had excellent regeneration ability, dispersibility, and stability. The fitting of kinetics, isotherms, and thermodynamics indicated the removal was endothermic and spontaneous, and involved some chemical reactions. The application evaluation of electroplating wastewater also shows that CoFe₂O₄@SiO₂-Ppy is an excellent adsorbent for Hg²⁺ ions from water.

Nanomaterials for the Removal of Heavy Metals from Wastewater

Removal of contaminants in wastewater, such as heavy metals, has become a severe problem in the world. Numerous technologies have been developed to deal with this problem. As an emerging technology, nanotechnology has been gaining increasing interest and many nanomaterials have been developed to remove heavy metals from polluted water, due to their excellent features resulting from the nanometer effect. In this work, novel nanomaterials, including carbon-based nanomaterials, zero-valent metal, metal-oxide based nanomaterials, and nanocomposites, and their applications for the removal of heavy metal ions from wastewater were systematically reviewed. Their efficiency, limitations, and advantages were compared and discussed. Furthermore, the promising perspective of nanomaterials in environmental applications was also discussed and potential directions for future work were suggested.

Biocompatible HA@Fe3 O4 @N-CDs hybrids for detecting and absorbing lead ion

The trinary hydroxyapatite@Fe₃ O₄ @N-doped carbon dots (HA@Fe₃ O₄ @N-CDs) hybrids were prepared by one-pot hydrothermal approach and utilized to detect and remove lead ion from aqueous solution. The structures and morphologies of as-obtained nanorod-like HA@Fe₃ O₄ @N-CDs hybrids were characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy measurements. These HA@Fe₃ O₄ @N-CDs hybrids possess good magnetism by magnetic hysteresis test and multi-colored fluorescence by the CLSM measurement. Furthermore, the as-obtained hybrids display excellent biocompatibility by MTT assay. Importantly, the trinary magnetic HA@Fe₃ O₄ @N-CDs hybrids as a green detector and adsorbent of Pb²⁺ were investigated. The influence of the different pH, the concentration of heavy metal, and the maximum adsorption capacity on removal efficiency was measured in detail. The maximum Pb²⁺ adsorption capacity on HA@Fe₃ O₄ @N-CDs hybrids is 450 mg/g. The kinetic mechanism was a pseudo-second order model, and the isotherm data was fitted well by the Langmuir isotherm and Freundlich model. Hence, the nanorod-like HA@Fe₃ O₄ @N-CDs hybrids could be a multifunctional material with significant potential applications in heavy metal detection and adsorption, bone tissue regeneration, magnetic therapy, and biomedicine. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2019.

Magnetic mesoporous TiO2 microspheres for sustainable arsenate removal from acidic environments

Unique magnetic mesoporous TiO₂ microspheres exhibit superior arsenate removal performance and high stability in acidic environments.