Simultaneous removal of Sb(III) and Sb(V) from mining wastewater by reduced graphene oxide/bimetallic nanoparticles

Advancing Antimony(III) Adsorption: Impact of Varied Manganese Oxide Modifications on Iron-Graphene Oxide-Chitosan Composites

Antimony (Sb) is one of the most concerning toxic metals globally, making the study of methods for efficiently removing Sb(III) from water increasingly urgent. This study uses graphene oxide and chitosan as the matrix (GOCS), modifying them with FeCl2 and four MnOx to form iron-manganese oxide (FM/GC) at a Fe/Mn molar ratio of 4:1. FM/GC quaternary composite microspheres are prepared, showing that FM/GC obtained from different MnOx exhibits significant differences in the ability to remove Sb(III) from neutral solutions. The order of Sb(III) removal effectiveness is MnSO4 > KMnO4 > MnCl2 > MnO2. The composite microspheres obtained by modifying GOCS with FeCl2 and MnSO4 are selected for further batch experiments and characterization tests to analyze the factors and mechanisms influencing Sb(III) removal. The results show that the adsorption capacity of Sb(III) decreases with increasing pH and solid-liquid ratio, and gradually increases with the initial concentration and reaction time. The Langmuir model fitting indicates that the maximum adsorption capacity of Sb(III) is 178.89 mg/g. The adsorption mechanism involves the oxidation of the Mn-O group, which converts Sb(III) in water into Sb(V). This is followed by ligand exchange and complex formation with O-H in FeO(OH) groups, and further interactions with C-OH, C-O, O-H, and other functional groups in GOCS.

Facile synthesis of Bi3O(OH)(AsO4)2 and simultaneous photocatalytic oxidation and adsorption of Sb(III) from wastewater

Antimony (Sb) decontamination in water is necessary owing to the worsening pollution which seriously threatens human life safety. Designing bismuth-based photocatalysts with hydroxyls have attracted growing interest because of the broad bandgap and enhanced separation efficiency of photogenerated electron/hole pairs. Until now, the available photocatalysis information regarding bismuth-based photocatalysts with hydroxyls has remained scarce and the contemporary report has been largely limited to Bi3O(OH)(PO4)2 (BOHP). Herein, Bi3O(OH)(AsO4)2 (BOHAs), a novel ultraviolet photocatalyst, was fabricated via the co-precipitation method for the first time, and developed to simultaneous photocatalytic oxidation and adsorption of Sb(III). The rate constant of Sb(III) removal by the BOHAs was 32.4, 3.0, and 4.3 times higher than those of BiAsO4, BOHP, and TiO2, respectively, indicating that the introduction of hydroxyls could increase the removal of Sb(III). Additionally, the crucial operational parameters affecting the adsorption performance (catalyst dosage, concentration, pH, and common anions) were investigated. The BOHAs maintained 85% antimony decontamination of the initial yield after five successive cycles of photocatalysis. The Sb(III) removal involved photocatalytic oxidation of adsorbed Sb(III) and subsequent adsorption of the yielded Sb(V). With the acquired knowledge, we successfully applied the photocatalyst for antimony removal from industrial wastewater. In addition, BOHAs could also be powerful photocatalysts in the photodegradation of organic pollutants studies of which are ongoing. It reveals an effective strategy for synthesizing bismuth-based photocatalysts with hydroxyls and enhancing pollutants' decontamination.

Efficient removal of Sb(III) from wastewater using selenium nanoparticles synthesized by Psidium guajava plant extract

Antimony (Sb) pollution in aquatic ecosystems has emerged as a critical environmental issue on a global scale, emphasizing the urgent need for cost-effective and user-friendly technologies to remove Sb compounds from water sources. In this study, a novel adsorbent, selenium nanoparticles (SeNPs), was synthesized using the aqueous extract of Psidium guajava L. leaves (AEP) for the purpose of eliminating Sb(III) from aqueous solutions. The biosynthesized SeNPs was characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray fluorescence spectrometer (XRF), Fourier Transform-Infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis techniques. Additionally, the removal efficiency of the SeNPs for Sb(III) was systematic investigated under the effects of SeNPs dose, temperature, pH and re-usability. The results of this study showed that the adsorption data fitted well into pseudo-second order model, while the Sips modeling demonstrated a high adsorption capacity (62.7 mg/g) of SeNPs for Sb(III) ions at 303.15 K from aqueous solution. The exothermic enthalpy change of - 22.59 kJ/mol and negative Gibbs free energy change assured the viability of the adsorption process under the considered temperature conditions. Surface functional groups on SeNPs like carboxyl, amide, hydroxyl, carbonyl, and methylene significantly facilitate the adsorption processes. Furthermore, the removal efficiencies of Sb in the two actual Sb mine wastewater samples were remarkably high, achieving nearly to 100% with 1.5 g/L SeNPs within 48 h. This outcome underscores the potential of SeNPs as a highly promising solution for efficiently remediating Sb from aquatic environments, owing to their cost-effectiveness, ease of regeneration, and rapid uptake capabilities.

Unveiling interfacial interaction between antimony oxyanions and boehmite nanorods: Spectroscopic evidence and density functional theory analysis

In natural environments, the fate and migratory behavior of metalloid contaminants such as antimony (Sb) significantly depend on the interfacial reactivity of mineral surfaces. Although boehmite (γ-AlOOH) is widely observed in (sub)surface environments, its underlying interaction mechanism with Sb oxyanions at the molecular scale remains unclear. Considering Sb-contaminated environmental conditions in this study, we prepared boehmite under weakly acidic conditions for use in the systematic investigation of interfacial interactions with Sb(III) and Sb(V). The as-synthesized boehmite showed a nanorod morphology and comprised four crystal facets in the following order: 48.4% (010), 27.1% (101), 15.0% (001), and 9.5% (100). The combined results of spectroscopic analyses and theoretical calculations revealed that Sb(III) formed hydrogen bonding outer-sphere complexation on the (100), (010), and (001) facets and that Sb(V) preferred to form bidentate inner-sphere complexation via mononuclear edge-sharing configuration on the (100), (001), and (101) facets and binuclear corner-sharing configuration on the (010) facet. These findings indicate that the facet-mediated thermodynamic stability of the surface complexation determines the interaction affinity toward the Sb species. This work is the first to document the contribution of boehmite to (sub)surface media, improving the ability to forecast the fate and behavior of Sb oxyanions at mineral-water interfaces.

Photochemical-promoted ZVI reduction for highly efficient removal of 4-chlorophenol and Cr(VI): Catalytic activity, performance and electron transfer mechanisms

Zero-valent iron (ZVI) reduction represents a promising methodology for water remediation, but its broad application is limited by two critical challenges (i.e., aggregation and passivation). Here, we report a hybrid strategy of photochemical-promoted ZVI reduction with high efficiency and reduction capacity for removing coexisting refractory pollutants in water. A composite material with Pd/Fe bimetallic nanoparticles supported onto semiconducting metal oxide (Pd/Fe@WO3-GO) was prepared and subsequently used as the model catalyst. By using the developed strategy with visible light as light source, this catalyst showed a remarkable catalytic performance for simultaneously eliminating 4-chlorophenol (4-CP) and Cr(VI), with dehalogenation rate as high as 0.43 min-1, outperforming the reported ZVI-based catalysts. A synergistic interaction of photocatalysis and ZVI reduction occurred in this strategy, where the interfacial electron transfer on particles surface were greatly strengthened with light irradiation. The activation was attributed to the dual functions of semiconducting material as support to disperse Pd/Fe nanoparticles and as (photoexcited) electron donor to directly trigger reduction reactions and/or indirectly inhibit the formation of oxides passivation layer. Both direct electron transfer and H*-mediated indirect electron transfer mechanisms were confirmed to participate in the reduction of pollutants, while the later was quantitatively demonstrated as the predominant reaction route. Importantly, this strategy showed a wide pH applicability, long-term durability and excellent catalytic performance in different real-water systems. This work provides new insights into ZVI reduction and advances its applications for the removal of combined organic and inorganic pollutants. The developed photochemical-promoted ZVI reduction strategy holds a great potential for practical applications.

Mining wastewater treatment technologies and resource recovery techniques: A review

Mining wastewater can have adverse effects on the ecosystem; thus, treatment before discharging into the environment is of utmost importance. This manuscript reports on the effect of mining wastewater on the environment. Moreover, the currently used, effective and commercialised mine wastewater treatment technologies such as SAVMIN®, SPARRO®, Biogenic sulphide, and DESALX® are reported in this study. These technologies integrate two or more separation processes, which have been proven to be effective for the high recovery of salts and water for reuse. Some of the technologies reported can significantly recover salts and >95% of water. Modern pilot-stage and laboratory-scale treatment systems used for the recovery and removal of metals are also reported herein. Since some treatment technologies can generate highly toxic sludge and other waste products, the management of the generated waste was also considered. Some studies have focused on the treatment of wastewater at the laboratory level using the adsorption process. Most adsorbents exhibit promising results; however, there is insufficient research on reusability, toxic sludge management, and the economic analysis of the systems. Moreover, the implementation of adsorption systems in wastewater is necessary. Furthermore, the integration of treatment systems to recover precious metals at low concentrations is desirable in addition to water reclamation to achieve circular mine water.

Investigating the potential of structurally defective UiO-66 for Sb (V) removal from tailing wastewater

Antimony contamination of tailings from the mining process remain attracted a great amount of concern. In this study, defective UiO-66-X crystal materials are rationally constructed using trifluoroacetic acid and hydrochloric acid as modulators for the removal of Sb(V) from actual tailing sand leachates. XRD and TG characterizations reveal that the number and kind of defects in UiO-66 are influenced by the type of modulators and the addition of trifluoroacetic acid makes UiO-66-TFA contain both cluster and ligand defects. Adsorption experiments show that UiO-66 and UiO-66-HCl achieve 100% removal of Sb(V) at pH 7.5 of the tailing sand leachate, and up to 90% removal of Sb(V) by the three materials at pH 2.5. It is noteworthy that the removal rate of Sb(V) by UiO-66-HCl is still satisfactory even under strongly acidic conditions at pH 0.5, with good potential for practical applications. Four kinetic models are used to fit the adsorption data and the analysis shows that the mechanism of Sb(V) adsorption by three adsorbent is all pseudo-second order and chemisorption acts as an important role in the adsorption process. In addition, the fixed bed adsorption experiments show that the material exhibit good prospects for practical applications.

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.

Separable alginate gel spheres encapsulated with La-Fe modified biochar for efficient adsorption of Sb(III) with high capacity

Sb and its compounds have been widely used in various industrial applications. Therefore, the preparation of Sb adsorbents with easy recovery and excellent adsorption levels is an urgent problem that must be resolved. By calcining and treating La/Fe metal-organic frameworks (MOF) biochar as a precursor, a loaded La-Fe-modified water hyacinth biochar was synthesised and used as a filler to synthesise iron alginate composite gel spheres, MBC/algFe. Through a series of static adsorption experiments, the effects of different filler addition ratios, solution pH, reaction time, coexisting ions, and other factors on the adsorption of Sb(III) were investigated. According to the Langmuir model, the maximum adsorption capacity of MBC/algFe at 25 ℃ was 277.8 mg·g-1. The adsorption mechanism mainly involved hydrogen bonding and metal-organic complexation interactions.

A critical review on adsorptive removal of antimony from waters: Adsorbent species, interface behavior and interaction mechanism

Antimony (Sb) has raised widespread concern because of its negative effects on ecology and human health. The extensive use of antimony-containing products and corresponding Sb mining activities have discharged considerable amounts of anthropogenic Sb into the environment, especially the water environment. Adsorption has been employed as the most effective strategy for Sb sequestration from water; thus, a comprehensive understanding of the adsorption performance, behavior and mechanisms of adsorbents benefits to develop the optimal adsorbent to remove Sb and even drive its practical application. This review presents a holistic analysis of adsorbent species with the ability to remove Sb from water, with a special emphasis on the Sb adsorption behavior of various adsorption materials and their Sb-adsorbent interaction mechanisms. Herein, we summarize research results based on the characteristic properties and Sb affinities of reported adsorbents. Various interactions, including electrostatic interactions, ion exchange, complexation and redox reactions, are fully reviewed. Relevant environmental factors and adsorption models are also discussed to clarify the relevant adsorption processes. Overall, iron-based adsorbents and corresponding composite adsorbents show relatively excellent Sb adsorption performance and have received widespread attention. Sb removal mainly depends on chemical properties of the adsorbent and Sb itself, and complexation is the main driving force for Sb removal, assisted by electrostatic attraction. The future directions of Sb removal by adsorption focus on the shortcomings of current adsorbents; more attention should be given to the practicability of adsorbents and their disposal after use. This review contributes to the development of effective adsorbents for removing Sb and provides an understanding of Sb interfacial processes during Sb transport and the fate of Sb in the water environment.

Recent advancements in antimony (Sb) removal from water and wastewater by carbon-based materials: a systematic review

Antimony (Sb) has been classified as a high-priority contaminant in the environment. Sb contamination resulting from the use of antimony-containing compounds in industry necessitates the development of efficient methods to remove it from water and wastewater. Adsorption is a highly efficient and reliable method for pollutants removal owing to its availability, recyclability, and low cost. Recently, carbonaceous materials and their applications for the removal of Sb from the aqueous matrices have received special attention worldwide. Herein, this review systematically summarizes the occurrence and exposure of Sb in the environment and on human health, respectively. Different carbon-based adsorbents have been classified for the adsorptive removal of Sb and their adsorption characteristics have been delineated. Recent development in the adsorption performance of the adsorbent materials for improving the Sb removal from the aqueous medium has been outlined. Further, to develop an understanding of the effect of different parameters like pH, competitive ions, and dissolved ions for Sb adsorption and subsequent removal have been discussed. A retrospective analysis of literature was conducted to present the adsorption behavior and underlying mechanisms involved in the removal of Sb using various adsorbents. Moreover, this study has identified emerging research gaps and emphasized the need for developing modified/engineered carbonaceous adsorbents to enhance Sb adsorption from various aqueous matrices.

Enhanced effect and mechanism of nano Fe-Ca bimetallic oxide modified substrate on Cu(II) and Ni(II) removal in constructed wetland

In this study, Fe₂O₃ nanoparticles (Fe₂O₃ NPs) and CaO NPs were loaded on the zeolite sphere carrier to create nano Fe-Ca bimetallic oxide (Fe-Ca-NBMO) modified substrate, which was introduced into constructed wetland (CW) to remove Cu(II) and Ni(II) via constructing "substrate-microorganism" system. Adsorption experiments showed that the equilibrium adsorption capacities of Fe-Ca-NBMO modified substrate for Cu(II) and Ni(II) were respectively 706.48 and 410.59 mg/kg at an initial concentration of 20 mg/L, 2.45 and 2.39 times of gravel. The Cu(II) and Ni(II) removal efficiencies in CW with Fe-Ca-NBMO modified substrate respectively reached 99.7% and 99.9% at an influent concentration of 100 mg/L, significantly higher than those in gravel-based CW (47.0% and 34.3%). Fe-Ca-NBMO modified substrate could promote Cu(II) and Ni(II) removal by increasing electrostatic adsorption, chemical precipitation, as well as the abundances of resistant microorganisms (Geobacter, Desulfuromonas, Zoogloea, Dechloromonas, and Desulfobacter) and functional genes (copA, cusABC, ABC.CD.P, gshB, and exbB). This study provided an effective method to enhance Cu(II) and Ni(II) removal of electroplating wastewater by CW with Fe-Ca-NBMO modified substrate.

Impact of coexisting components in acid mine drainage on Sb(Ⅲ) oxidation by biosynthesized iron nanoparticles

Despite the oxidation mechanism of antimonite (Sb(Ⅲ)) by biosynthesized iron nanoparticles (Fe NPs) has been reported, the impact of coexisting components in acid mine drainage (AMD) on the Sb(III) oxidation by Fe NPs is unknown. Herein, how the coexisting components in AMD affect Sb(Ⅲ) oxidation by Fe NPs was investigated. Firstly, Fe NPs achieved complete oxidation of Sb(Ⅲ) (100%), while only 65.0% of Sb(Ⅲ) was oxidized when As(Ⅲ) was added, due to competitive oxidation between As(Ⅲ) and Sb(Ⅲ), which was verified by characterization analysis. Secondly, the decline in solution pH improved Sb(Ⅲ) oxidation from 69.5% (pH 4) to 100% (pH 2), which could be attributed to the rise of Fe³⁺ in solution promoting the electron transfer between Sb(Ⅲ) and Fe NPs. Thirdly, the oxidation efficiencies of Sb(Ⅲ) fell by 14.9 and 44.2% following the addition of oxalic and citric acid, respectively, resulting from the fact that these two acids reduced the redox potential of Fe NPs, thereby inhibiting Sb(Ⅲ) oxidation by Fe NPs. Finally, the interference effect of coexisting ions was studied, where PO₄^3- significantly reduced Sb(Ⅲ) oxidation efficiency due to the occupation of the surface-active sites on Fe NPs. Overall, this study has significant implications for the prevention of Sb contamination in AMD.