Recent advances in removal techniques of vanadium from water: A comprehensive review

Removal of vanadium(V) ions from acidic water using reusable manganese oxide sorbents

Manganese oxide (MnOx) was studied for its ability to adsorb vanadium (V) ions for applications in acidic water treatment. Three MnOx types: naturally-occurring (NatMnO), commercially-derived (ComMnO), and laboratory synthesised (SynMnO) were examined in batch systems under varying pH, adsorbent dosage, ionic strength, and contact time. The greatest V sorption occurred at acidic pH, following the order: NatMnO > SynMnO > ComMnO, with maximum adsorption capacities of 54.0, 26.0, and 10.4 mg/g, respectively (at pH 3.0, mass/volume ratio of 2 g/L, concentration of 100 mg/L, 24 hours). Adsorption equilibrium data best fit the Freundlich isotherm, indicating multilayer adsorption, while kinetic data followed a two-constant rate model, suggesting both physical and chemical sorption. Solution pH was found to have a significant impact, with V removal by MnOx most effective at low pH, likely due to the negative zeta potential of the MnOx under such conditions. MnOx reusability was investigated using repeated sorption and desorption experiments with 0.1 M HCl, 0.1 M NaOH, and deionised water to regenerate the MnOx. The regenerated MnOx exhibited similar or enhanced ability to sorb V ions from solution. Overall, these results confirm the unique ability of MnOx as a reusable sorbent for V removal from acidic water, while also enhancing our mechanistic understanding of the removal process. This finding supports the development of sustainable solutions for acidic water treatment, contributing to efforts to address this critical environmental challenge.

Novel metabolic pathways of bioelectrochemical vanadate reduction by Thiobacillus denitrificans without exogenous electron donor supplementation in groundwater

Microbially mediated vanadate [V(V)] reduction is well accepted as a sustainable approach for remediating V-polluted groundwater. However, this process relies on exogenous electron donors, which is challenging to control precisely and inject into aquifer. In this study, bioelectrochemical V(V) reduction by autotrophic Thiobacillus denitrificans was demonstrated without exogenous electron donor supplementation. At an applied voltage of 0.9 V, 94.5 ± 0.95 % of V(V) was removed within 14 d V(V) was mainly bioreduced at the cathode. Insoluble tetravalent V was the main reduction product, distributed both outside and inside of cells. Electrochemical analysis, transcriptomics, RT-qPCR and substance quantification analysis collectively suggested that extracellular V(V) reduction was mediated by cytochrome c and extracellular polymeric substances. Intracellular V(V) reduction was catalyzed by sulfate-, chromate-, and denitrification-related reductases and achieved by redox components including NADH, Fe-S clusters, and quinones in respiratory chain. Particularly, the newly V(V) reduction pathways of the functional genes aprB and iscA were further confirmed via in vitro trials involving heterologous expression and protein catalysis assays. This study provided an innovative strategy for V(V) bioremediation in groundwater and gained novel insight into molecular mechanisms of V(V) bioreduction.

New Insights into the Adsorption Mechanism of Vanadium Through Quaternary Ammonium Salt-Functionalized SiO2: Synergistic Experiments Utilizing Energy Decomposition Analysis

Introducing organic functional groups to adsorbent surfaces enhances vanadium adsorption, an effective strategy for vanadium enrichment. In a quest for a profounder comprehension of the above adsorption mechanism, this study synthesized five types of quaternary ammonium salt-functionalized silica (QAS-SiO2) and investigated the influence of functional groups, pH values, contact time, and temperature on vanadium (V) adsorption. The results indicated that the optimal QAS-SiO2 (SiO2@DMOA) achieved a vanadium adsorption rate of 99.40% and a maximum adsorption capacity of 39.16 mg g-1. SiO2@DMOA exhibited favorable adsorption selectivity for V over chromium (Cr), with a maximum separation factor (βV/Cr) of 135.42 at pH 3.3. SiO2@DMOA maintained efficient adsorption performance over five repeated cycles. A fusion of adsorption trials with energy decomposition analysis (EDA) tentatively unveiled that both chemical bonds and non-bonding interactions contributed to the interaction energy between organic functional groups and vanadium. Among them, chemical bonds accounted for 80.26%, while non-bonding interactions accounted for 19.74%. Based on EDA analysis, the interaction characteristics of different structural quaternary ammonium salts with vanadium in adsorption and extraction processes are discussed. Additionally, steric hindrance, the charge of the vanadium species, polarizability, and solvation effects, all played significant roles in the adsorption process.

Insights into the hydrogen-fueled bioreduction of vanadium(V) by marine Shewanella sp. FDA-1: Process and mechanism

Microbial-driven V(V) reduction plays a crucial role in its biogeochemical cycle, yet the mechanisms underlying this bioreduction remain inadequately understood. While the effectiveness of organic compounds as electron donors in facilitating bacterial reduction of V(V) has been established, the role of inorganic electron donors in initiating this process at the level of pure cultured bacteria has not been explored. In this study, we report on a marine Shewanella sp. FDA-1 that utilizes hydrogen (H2) as an energy source to reduce V(V). In addition, the reduction mechanism was investigated through a combination of genomics, RT-qPCR, heterologous expression of key proteins, extracellular secretion analyses, and electron transfer activity assays. Our results demonstrate that H2 serves as an effective electron donor, enabling Shewanella sp. FDA-1 to reduce V(V) across various salinities (2-7 %) and pH values (5-9). When exposed to 5 mM V(V), the presence of 1-20 mL of H2 resulted in V(V) bioreduction rates ranging from 0.039 to 0.11 h-1 (R2 > 0.73). Amorphous V(IV) compounds were characterized as reduction products using XRD, XPS, FTIR, and SEM. Mechanistic studies indicate that the glutathione system, cytochromes, and extracellular substances such as riboflavin play important roles in V(V) reduction (p < 0.05). Furthermore, our findings reveal that the addition of H2 and lactate triggers different response sequences among these three reduction pathways, suggesting distinct reduction mechanisms between organic and inorganic electron donors. These insights enhance our understanding of microbial vanadium transformation and provide valuable guidance for developing novel H2-based remediation technologies for vanadium-contaminated environments.

Green chemistry: magnetic dispersive solid phase extraction for simultaneous enrichment and determination of V, Ni, Ti and Ga in water samples by HR-CS ETAAS

This work presents a straightforward, highly sensitive, and cost-effective method for the simultaneous determination of V, Ti, Ni and Ga by high resolution-continuum source electrothermal atomic absorption spectrometer (HR-CS ETAAS) in aqueous environmental samples (tap and seawater samples). The system is based on retention of the analyte onto a novel magnetic nanomaterial (M@GO magnetic graphene oxide) functionalised with methylthiosalicilate (MTS). The formed complexes between the M@GO-MTS and the target analytes were broken, adding 1 mL of nitric acid (6%) and sonication for 5 min. The optimized method achieved detection limits of 0.71 μg L-1 for Ti, 0.20 μg L-1 for V, 0.04 μg L-1 for Ga, 0.66 μg L-1 for Ni. The accuracy of the proposed method was demonstrated by analysing two certified reference materials and by determining the analyte content in spiked environmental water samples. The results obtained using this method were in good agreement with the certified values of the standard reference materials, and the recoveries for the spiked tap water and seawater samples ranged from 94% to 120%.

Vanadium (V) reduction and the performance of electroactive biofilms in microbial fuel cells with Shewanella putrefaciens

The electron transfer ability of biofilms significantly influences the electrochemical activity of microbial fuel cells (MFCs). However, there is limited understanding of pentavalent vanadium (V(V)) bioreduction and microbial response characteristics in MFCs. In this study, the effect of gradient concentrations of V(V) on the performance of EABs with Shewanella putrefaciens in MFCs was investigated. The results showed that as V(V) concentration increased (0-100 mg/L), the voltage output, power densities, polarization, and electrode potential decreased. V(V) was found to act as an electron acceptor and was reduced during MFCs operation, with a yield of 83.16% being observed at 25 mg/L V(V). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) indicated declining electrochemical performance of the MFCs with escalating V(V) concentration. The content of protein and polysaccharide from extracellular polymeric substances (EPS) in anodic biofilms increased to 66.75 and 49.15 mg/L at 75 mg/L V(V), respectively. Three-dimensional fluorescence spectroscopy confirmed increased humic substances in EPS extraction with V(V) exposure. The functional genes narG, nirK, and gor involved in V(V) reduction were upregulated with rising V(V) concentration through quantitative polymerase chain reaction (qPCR) analysis. Additionally, riboflavin, cytochrome c, nicotinamide adenine dinucleotide (NADH), and electron transport system activity (ETSA), key indicators for assessing electron transfer behavior, exhibited a negative correlation with various V(V) concentrations, decreasing by 31.81%, 57.14%, 67.39%, and 51.41%, respectively, at a concentration of 100 mg/L V(V) compared to the blank control. These findings contribute valuable insights into the response of EABs to V(V) exposure, presenting potential strategies for enhancing their effectiveness in the treatment of vanadium-contaminated wastewater.

Enhanced phytoremediation of vanadium using coffee grounds and fast-growing plants: Integrating machine learning for predictive modeling

Vanadium (V) contamination posed a significant environmental challenge, while phytoremediation offered a sustainable solution. Phytoremediation performance was often limited by the slow growth cycles of traditional plants. A novel approach to enhancing V phytoremediation by integrating coffee grounds with fast-growing plants such as barley grass, wheat grass, and ryegrass was investigated in this study. The innovative use of coffee grounds leveraged not only their nutrient-rich composition but also their ability to reduce oxidative stress in plants, thereby significantly boosting phytoremediation efficiency. Notably, ryegrass achieved 48.7% V5+ removal within 6 d with initial 20 mg/L V5+ (0.338 mg/L·d·g ryegrass). When combined with coffee grounds, V5+ removal by using wheat grass increased substantially, rising from 30.51% to 62.91%. Gradient Boosting and XGBoost models, trained with optimized parameters including a learning rate of 0.1, max depth of 3, and n_estimators of 300, were employed to predict and optimize V5+ concentrations in the phytoremediation process. These models were evaluated using mean squared error (MSE) and coefficient of determination (R2) metrics, achieving high predictive accuracy (R2 = 0.95, MSE = 1.20). Feature importance analysis further identified the initial V5+ concentration and experimental duration as the most significant factors influencing the model's predictions. The addition of coffee grounds not only mitigated the stress of heavy metals on ryegrass, leading to significant reductions in CAT (87.2%), POD (98.8%), and SOD (39.2%) activities in ryegrass roots, but also significantly altered the microbial community abundance in the plant roots. This research provided an innovative enhancement to traditional phytoremediation methods, and established a new paradigm for using machine learning to predict and optimize V5+ remediation outcomes. The effectiveness of this technology in multi-metal polluted environments warrants further investigation in the future.

Emulsion liquid membrane (ELM) enhanced by nanoparticles and ionic liquid for extracting vanadium ions from wastewater

Emulsion liquid membrane (ELM) stands out as an extraction process that has drawn much attention due to its promising prospects in industrial wastewater treatment technology. Nevertheless, the pivotal challenge is to reach high membrane stability to overcome the obstacle of applying ELM at the industrial scale. In this study, ELM was boosted by using nanoparticles (superparamagnetic iron oxide (Fe2O3)) in the stripping phase (W1) and ionic liquid (1-methyl-3-octyl-imidazolium-hexafluorophosphate [OMIM][PF6) in the oil phase (O) for recovering/extracting vanadium from synthetic wastewater to near completion and at the same time enhancing emulsion stability to be appropriate for industrial application. The vanadium recovery/extraction percentage has been raised significantly in 3 min to 99.6% when adding 0.01% (w/w) Fe2O3 NPs (20 to 50 nm in size) in the internal phase (W1) and 5% (v/v) [OMIM]PF6 ionic liquid in the oil phase (O). Also, the emulsion stability was considerably improved, and the leakage percentage was reduced to 16% after 3 days. The results of this study could be used in the future to remove additional heavy metal ions from industrial effluents.

Is Cladophora fracta an efficient tool of accumulating critical raw materials from wastewater and there a potential health risk of use of algae as organic fertilizer?

 In this study investigation of accumulations of critical raw materials (cobalt (Co), antimony (Sb), vanadium (V), lanthanum (La) and tungsten (W)) from wastewater by using C. fracta were aimed. Besides, assessment of the potential health risks in terms of the use of organic fertilizer obtained from the macroalga to be harvested from the treatment were also aimed. Highest Co, Sb, V, La and W accumulations by algae in reactor were 125±6.2%, 201.25±10%, 318.18±15%, 357.97±18%, and 500±25%, respectively. When compared with control, Co, Sb, V, La and W in algae increased 2.25, 3.01, 4.18, 4.58, and 6 times, respectively. The algae was very high bioaccumulative for Co and La. Highest MPI was calculated as 3.94. Non-carcinogenic risk of CRMs according to different exposure types (ingestion, inhalation, and dermal) were calculated for man, woman and child. There is not any non-carcinogenic risk from the investigated exposure ways of algae as organic fertilizer.

Hyper-accumulation of vanadium in animals: Two sponges compete with urochordates

Vanadium (V) concentrations in organisms are usually very low. To date, among animals, only some urochordate and annelid species contain very high levels of V in their tissues. A new case of hyper-accumulation of V in a distinct animal phylum (Porifera), namely, the two homoscleromorph sponge species Oscarella lobularis and O. tuberculata is reported. The measured concentrations (up to 30 g/kg dry weight) exceed those reported previously and are not found in all sponge classes. In both Oscarella species, V is mainly accumulated in the surface tissues, and in mesohylar cells, as V(IV), before being partly reduced to V(III) in the deeper tissues. Candidate genes from Bacteria and sponges have been identified as possibly being involved in the metabolism of V. This finding provides clues for the development of bioremediation strategies in marine ecosystems and/or bioinspired processes to recycle this critical metal.

Superior Removal of Vanadium(V) from Simulated Groundwater with a Fe-Based Metal-Organic Framework Immobilized on Cotton Fibers

A suitable adsorbent is essential in the process of removing hazardous vanadium(V) from actual groundwater. In this work, MIL-88A(Fe)/cotton (MC) was employed to eliminate V(V) from simulated vanadium-contaminated groundwater. The findings demonstrated that MC exhibited an exceptional performance in removing V(V), displaying a maximum adsorption capacity of 218.71 mg g-1. MC exhibits great promise as an adsorbent for V(V) elimination in an extensive pH range spanning 3 to 11. Even in the presence of high levels of competing ions such as Cl-, NO3-, and SO42-, MC demonstrated remarkable specificity in adsorbing V(V). The results of column experiments and co-occurring ions influence tests indicate that MC is a potential candidate for effectively treating actual vanadium-contaminated groundwater. The effluent could meet the vanadium content restriction of 50 μg L-1 required in China's drinking water sources. Regeneration of MC can be performed easily without experiencing significant capacity loss. The results obtained from this research indicate the promising potential of MC in mitigating vanadium pollution.

Spatiotemporal characterization of vanadium at the sediment-water interface of a multi-ecological lake

As an emerging environmentally harmful metal, vanadium (V) deserves significant research attention due to its hazardous concentrations in aquatic environments. However, the research on the characterization of V in sediment-water interface (SWI) remains limited. In this study, seasonal sampling was conducted in algal- and macrophyte-dominated zones via the method of in situ high-resolution diffusive gradients in thin films (DGT). The concentration of dissolved V in water in algal-dominated regions (12 sites) exceeded the long-term ecotoxicology limit of 1.2 μg⋅L-1. Seasonal variations of chemical speciation of V were observed in three ecological sites. DGT-labile V at the SWI exhibited two basic patterns associated with eutrophic status, one showing sharply decreasing gradients in the vicinity of the SWI and the other showing the absence of diffusion gradient. Positive correlations were observed between the water-dissolved V and the DGT-labile V, indicating DGT-labile V is a sensitive indicator for the release of V from sediment into water. Moreover, the mobility of V was influenced by the reduction of Fe(hydr)oxides and complexation with organic matter, in particular, during periods of algal blooms. It is suggested that V contamination at the SWI of algal-dominated zones deserves additional attention.

Recent advances in removal of inorganic anions from water by chitosan-based composites: A comprehensive review

Chitosan is a modified natural carbohydrate polymer that has been found in the exoskeletons of crustaceans (e.g., lobsters, shrimps, krill, barnacles, crayfish, etc.), mollusks (octopus, oysters, squids, snails), algae (diatoms, brown algae, green algae), insects (silkworms, beetles, scorpions), and the cell walls of fungi (such as Ascomycetes, Basidiomycetes, and Phycomycetes; for example, Aspergillus niger and Penicillium notatum). However, it is mostly acquired from marine crustaceans such as shrimp shells. Chitosan-based composites often present superior chemical, physical, and mechanical properties compared to single chitosan by incorporating the benefits of both counterparts in the nanocomposites. The tunable surface chemistry, abundant surface-active sites, facilitation synthesize and functionalization, good recyclability, and economic viability make the chitosan-based materials potential adsorbents for effective and fast removal of a broad range of inorganic anions. This article reviews the different types of inorganic anions and their effects on the environment and human health. The development of the chitosan-based composites synthesis, the various parameters like initial concentration, pH, adsorbent dosage, temperature, the mechanism of adsorption, and regeneration of adsorbents are discussed in detail. Finally, the prospects and technical challenges are emphasized to improve the performance of chitosan-based composites in actual applications on a pilot or industrial scale.

Nitrogen-rich carbon composite fabricated from waste shrimp shells for highly efficient oxo-vanadate adsorption-coupled reduction

Protein, calcium carbonate, and chitin are abundant in shrimp shells. In this study, chemical treatment followed by hydrothermal carbonization was used to synthesize the nitrogen-rich hydrochar (HSHC) from shrimp shells. The untreated hydrochar exhibited a higher amount of calcium (25.37%) and less amount of nitrogen (2.68%) with alkaline pH (9.1). Interestingly chemical pre-treatment on shrimp shells boosted the nitrogen content to 6.81% and eliminated the calcium while controlling the pH to 6.4, which was beneficial for oxo-vanadate removal. The HSHC achieved vanadium(V) adsorption capacity of 21.20 mg/g at an optimal solution pH of 3.0, whereas the pristine hydrochar performed poorly (0.66 mg/g). The abundance of oxygen and nitrogen-based functional groups that developed through the chemical treatment resulted in improved adsorption coupled reduction performance of HSHC. This study proposed an inexpensive and environmentally friendly method for converting waste shrimp shells into value-added adsorbent.

Vanadium mobilization and redistribution during mineral transformation of vanadium-titanium magnetite tailings with different weathering degrees

Due to the long-term open stockpile, the release of vanadium (V) from V-containing tailings will cause continuous V pollution in the mining area. Previous studies on the concentration and speciation of V primarily focused on surface tailings at a regional scale. However, the mobilization and redistribution of V within the tailing profile during the mineral transformation of tailings remain unclear. Herein, a series of concentrations of V(V) (0-200 mg L-1) solutions were added to the vanadium‑titanium magnetite tailings at different depths separately to simulate the redistribution of dissolved V released from tailings in the solid phase of tailings. During the 56-day incubation, the concentrations of aqueous V in the surface tailings were significantly lower than those in the deep tailings under the same level of V(V) treatment, indicating that the shallow tailings had a stronger immobilization capacity for V than the deep tailings. Morphological analysis and color overlays of the elements demonstrated that most of V was immobilized into the tailings and adsorbed or precipitated by the Fe (hydr)oxides in the tailings in 200 mg L-1 V(V) treatment. This portion of V mainly occurred in acid-soluble and reducible fractions in the tailings after a 7-day incubation, accounting for >71.7 % of the total V. However, these two factions of V with high bioavailability were gradually mineralized over time and transferred to residual V, which is difficult to move and has low bioavailability. Mineral phase analysis revealed that additional V(V) favored the formation of melanovanadite (Ca2V8O20·10H2O) and chromium vanadium oxide (Cr2V4O13) in the tailings. This study reveals that the dissolved V influenced the fractionation and redistribution of solid-phase V during tailing weathering, improving the understanding of the geochemical processes of V in tailing profiles and providing important guidance for the management of V-containing tailings.

Cyanobacterial blooms increase the release of vanadium through iron reduction and dissolved organic matter complexation in the sediment of eutrophic lakes

Vanadium (V), a hazardous environmental contaminant, can be highly toxic to aquatic or even human life. Nonetheless, knowledge of its redox geochemistry and mobility in sediments, especially those of eutrophic lakes, remains limited. In this study, we combined in situ high-resolution sampling and laboratory simulation experiments for monitoring soluble and labile V to reveal the mobilization mechanism of V in the sediment of Lake Taihu. The results showed that the concentration of soluble V (1.18-5.22 µg L-1) exceeded the long-term ecotoxicology limitation proposed by the government of the Netherlands. The highest value appeared in summer (July to September), with an average concentration of 3.87 µg L-1, which exceeded the short-term exposure limit. The remobilization of V in summer was caused by the combined effect of the reduction of Fe(hydr)oxides and dissolved organic matter (DOM) complexation, which accelerated the release of associated Fe-bound V and increased the solubility of DOM-V. Additionally, V showed high mobility in winter, owing to the species of V(Ⅲ)/V(Ⅳ) being oxidized to V(Ⅴ) with higher solubility. It is noteworthy that the elevated remobilization of V in sediments increases the risk of V release from sediments, which poses the threat of water V pollution in Lake Taihu.

Soil amendments for vanadium remediation: a review of remediation of vanadium in soil through chemical stabilization and bioremediation

Immobilization of vanadium (V) in soils is one option to prevent groundwater contamination and plant uptake. Phytoremediation, microbial remediation, and chemical stabilization using soil amendments are among the leading environmentally friendly and economically feasible techniques in V remediation. Soil amendments were used to reduce V mobility by immobilizing it in the soil matrix through chemical stabilization, while bioremediation methods such as phytoremediation and microbial remediation were used to remove V from contaminated soils. Vanadium exists in several species and among them V5+ species are the most prevalent, toxic, and soluble form and present as a negatively charged ion (H2VO4- and HVO42-) in oxic soils above pH 4. Amendments used for chemical stabilization can change the physicochemical properties enhancing immobility of V in soil. The pH of the soil environment, point of zero charge of the colloid surface, and redox conditions are some of the most important factors that determine the efficiency of the amendment. Commonly used amendments for chemical stabilization include biochar, zeolites, organic acids, various clay minerals and oxides of elements such as iron, titanium, manganese, and aluminum. For bioremediation, chelating agents and microbial communities are used to mobilize V to enhance phyto-or microbial-extraction procedures. The objectives of this review were to discuss remediation methods of V while considering V speciation and toxicity in soil, and soil amendment application for V removal from soil. The information compiled in this review can guide further research on soil amendments for optimal V remediation in largely contaminated industrial sites.

Enhanced selective separation of vanadium(V) and chromium(VI) using the CeO2 nanorod containing oxygen vacancies

Adsorption of vanadium from wastewater defends the environment from toxic ions and contributes to recover the valuable metal. However, it is still challenging for the separation of vanadium (V⁵⁺) and chromium (Cr⁶⁺) because of their similar properties. Herein, a kind of CeO₂ nanorod containing oxygen vacancies is facilely synthesized which displays ultra-high selectivity of V⁵⁺ against various competitive ions (i.e., Fe, Mn, Cr, Ni, Cu, Zn, Ga, Cd, Ba, Pb, Mg, Be, and Co). Moreover, a large separation factor (SF_V/Cr) of 114,169.14 for the selectivity of V⁵⁺ is achieved at the Cr⁶⁺/V⁵⁺ ratio of 80 with the trace amount of V⁵⁺ (~ 1 mg/L). The results show that the process of V⁵⁺ uptake is the monolayer homogeneous adsorption and is controlled by external and intraparticle diffusions. In addition, it also shows that V⁵⁺ is reduced to V³⁺ and V⁴⁺ and then formation of V-O complexation. This work offers a novel CeO₂ nanorod material for efficient separation of V⁵⁺ and Cr⁶⁺ and also clarifies the mechanism of the V⁵⁺ adsorption on the CeO₂ surface.

A sustainable vanadium bioremediation strategy from aqueous media by two potential green microalgae

Globally, environmental concerns are rapidly growing due to increasing pollution levels. Vanadium is a hazardous heavy metal that poses health issues with an exposure concentration of about 2 ppm. It is regularly discharged by some industries and poses an environmental challenge. There are no sustainable green treatment methods for discharged effluents to mitigate vanadium threats to humans and the environment. In this study, the goal was to develop a green, sustainable method for removing vanadium and to utilize the produced biomass for biofuels, thus offsetting the treatment cost. Microalgae Chlorella sorokiniana SU1 and Picochlorum oklahomensis were employed for vanadium (III) treatment. The maximum removal was 25.5 mg L^-1 with biomass and lipid yields of 3.0 g L^-1 and 884.4 mg L^-1 respectively after 14 days of treatment. The vanadium removal capacity by microalgae was further enhanced up to 2-2.7 folds while optimizing the key parameters, pH, and temperature before removing biomass from the liquid phase. FTIR is used to analyse the reactive groups in algal cell walls to confirm vanadium adsorption and to understand the dominant and quantitative interactions. Zeta potential analysis helps to find out the most suitable pH range to facilitate the ionic bonding of biomass and thus maximum vanadium adsorption. This study addresses regulating external factors for enhancing the removal performance during microalgal biomass harvesting, which significantly enhances the removal of vanadium (III) from the aqueous phase. This strategy aims to improve the removal efficiency of microalgal treatment at an industrial scale for the bioremediation of vanadium and other inorganic pollutants.

Study on the coordination conduct and kinetic insights within the oxo-vanadate and organic reductive nitrogen and sulfur functionalities during the reduction coupled adsorption processes: Implications in practical applications

Vanadium(V) is arising wastewater contaminant recently. Although bio-reduction of vanadium(V) is effective, the knowledge of electron transfer pathways and coordination nature by cellular organic functionalities is seriously lacking. Herein, the coordination conduct and kinetic modes for the reduction of V(V) by organic nitrogen and sulfur functionalities in working pHs are comprehensively investigated for the first time. The kinetics follow 3 steps; (1) diffusion of V(V) species, (2) reduction of V(V) to V(IV), and (3) adsorption of existing V species. The diffusion of V(V) is controlled by the protonated =NH₂⁺, -SH₂⁺, -CSH⁺ functional groups and oxo-vanadate speciation. The reduction of V(V) to V(IV) was efficient by -SH than =NH, -NH- , because of the higher oxidation potential of sulfur and which acted as the sole electron donor in the process. The coordination of V(V)/V(IV) species interacted with oxygen, nitrogen and sulfur atoms via parallel orientation and leads to multi-docking or single-ionic interactions, revealing the previously unrecognized track. Hence, the system tested in four types of wastewaters with different pHs and resulted the comprehensive practical applicability of the system. This study proposes a novel tactic to design an efficient V(V) wastewater treatment system by considering its water parameters.

Effect of Cu loading content on the catalytic performance of Cu-USY catalysts for selective catalytic reduction of NO with NH3

Series of Cu-USY zeolite catalyst with different Cu loading content were synthesized through simple impregnation method. The obtained catalysts were subjected to selective catalytic reduction of NO_x with NH₃ (NH₃-SCR) performance evaluation, structural/chemical characterizations such as X-ray diffraction (XRD), N₂ adsorption/desorption, H₂ temperature-programmed reduction (H₂-TPR), NH₃ temperature-programmed desorption (NH₃-TPD) as well as detailed in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments including CO adsorption, NH₃ adsorption and NO+O₂ in situ reactions. Results show that Cu-USY with proper Cu loading (in this work 5Cu-USY with 5 wt.% Cu) could be promising candidates with highly efficient NH₃-SCR catalytic performance, relatively low byproduct formation and excellent hydrothermal stability, although its SO₂ poisoning tolerability needs alleviation. Further characterizations reveal that such catalytic advantages can be attributed to both active cu species and surface acid centers evolution modulated by Cu loading. On one hand, Cu species in the super cages of zeolites increases with higher Cu content and being more conducive for NH₃-SCR reactivity. On the other hand, higher Cu loading leads to depletion of Brønsted acid centers and simultaneous formation of abundant Lewis acid centers, which facilitates NH₄NO₃ reduction via NH₃ adsorbed on Lewis acid centers, thus improving SCR reactivity. However, Cu over-introduction leads to formation of surface highly dispersed CuO_x, causing unfavorable NH₃ oxidation and inferior N₂ selectivity.

Vertically co-distributed vanadium and microplastics drive distinct microbial community composition and assembly in soil

Vanadium (V) and microplastics in soils draw increasing attention considering their significant threats to ecosystems. However, little is known about the vertical co-distribution of V and microplastics in soil profile and their combined effects on microbial community dynamics and assembly. This study investigated the spatial distribution of V and microplastics in the soils at a V smelting site and the associated microbial community characteristics along the vertical gradient. Both V and microplastics were found in the 50 cm soil profile with average concentrations of 203.5 ± 314.4 mg/kg and 165.1 ± 124.8 item/kg, respectively. Topsoil (0-20 cm) and subsoil (20-50 cm) displayed distinct microbial community compositions. Metal-tolerant (e.g., Spirochaeta, Rubellimicrobium) and organic-degrading (e.g., Bradyrhizobium, Pseudolabrys) taxa as biomarkers were more abundant in the topsoil layer. V and microplastics directly affected the microbial structure in the topsoil and had indirect influences in the subsoil, with direct impacts from organic matter. In topsoil, deterministic processes were more prevalent for community assembly, whereas stochastic processes governed the subsoil. The interspecific relationship was closer in topsoil with greater network complexity and higher modularity. These findings promote the understanding of distinct heterogeneity of microbial communities jointly driven by V and microplastics in soil environment.

Vanadium(V) Removal from Aqueous Solutions and Real Wastewaters onto Anion Exchangers and Lewatit AF5

Adsorption abilities of weakly (Purolite A830), weakly basic/chelating (Purolite S984), and strongly basic (Lewatit MonoPlus SR7, Purolite A400TL, Dowex PSR2, Dowex PSR3) ion exchange resins of different functional groups and microporous Lewatit AF5 without functional groups towards vanadium(V) ions were studied in batch and column systems. In the batch system, the influence of the sorbent mass (0.01–0.1 g), pH (2–10), the phase contact time (1–1440 min),and the initial concentration (5–2000 mg/L) were studied, whereas in the column system, the initial concentrations (50, 100, and 200 mg/L) with the same bed volume and flow rate (0.4 mL/min) were studied. Desorption agents HCl and NaOH of 0.1–1 mol/L concentration were used for loaded sorbent regeneration. The pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models as well as the Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models were used to describe kinetic and equilibrium data to acquire improved knowledge on the adsorption mechanism. The desorption efficiency was the largest using 0.5 mol/L NaOH for all sorbents under discussion. Purolite S984, Purolite A830, and Purolite A400TL, especially Purolite S984, are characterized by the best removal ability towards vanadium(V) from both model and real wastewater.

Fly ash derived calcium silicate hydrate as a highly efficient and fast adsorbent for Cu(ii) ions: role of copolymer functionalization

The environmental issues caused by heavy metal accumulation from polluted water are becoming serious and threaten human health and the ecosystem. The adsorption technology represented by calcium silicate hydrate has attracted much attention, but suffers from high manufacturing costs and poor stability bottlenecks. Here, we have proposed a "trash-to-treasure" conversion strategy to prepare a thin sheet calcium silicate hydrate material (ACSH) using solid waste fly ash as silicon source and a small amount of Acumer2000 as modifier. The obtained materials showed fast adsorption rates, superior adsorption capacities and remarkable long-term stability for Cu(ii) removal. Under the conditions of 0.5 g L-1 adsorbent concentration and 100 mL Cu(ii) solution with a concentration of 100 mg L-1, ACSH can adsorb 95.6% Cu(ii) within 5 min. The adsorption isotherms conformed to Langmuir models and the maximum adsorption capacity was 532 mg g-1. Using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, specific surface area and pore structure analysis, it was found that the excellent adsorption performance could be attributed to the ultrahigh surface area (356 m2 g-1), abundant pores and multiple active sites induced by Acumer2000 modification. Moreover, the encapsulation effect from carboxylate and long carbon chains in Acumer2000 endowed modified samples with strong corrosion resistance to CO2, which effectively inhibited the formation of by-product CaCO3 and retained the remarkable adsorption performance for more than 100 days. Interestingly enough, the advantages of ACSH in economy and performance could been maintained in ACSH based adsorptive membranes. This work is of great significance for solid waste utilization as well as the preparation of high quality, cost-effective and long-term stability calcium silicate hydrate materials.

Adsorption of vanadium (V) ions from the aqueous solutions on different biomass-derived biochars

The paper presents the results of the studies on the vanadium (V) ions removal from the aqueous solutions in the adsorption process on biochars from different biomass types (cow manure BC1, wet distiller grains BC2, spent mushroom substrates BC3). The adsorbents were characterized by means of the SEM-EDS, FTIR, XRD and XPS techniques. The influence of adsorbent type and basic process parameters, such as pH and metal ion concentration in aqueous phase, adsorbent dose and time of contact of phases on the efficiency of V(V) was determined. Based on the obtained results, the mechanism and kinetics of the adsorption processes occurring on the biochar originating from the wet distiller grains as adsorbents with the greatest affinity for the V(V) ions were characterized, using isotherm models of Langmuir, Freundlich, Temkin and Dubinin-Radushkevich and pseudo-first-order, pseudo-second-order as well as intraparticle diffusion kinetic models. Under the constant process conditions (pH = 3.0; m = 0.5 g; c₀ = 50 mg/L) the order of V(V) ions removal from aqueous solutions was as follows: BC2 > BC1 = BC3. The biochar BC2 exhibited the maximum sorption capacity of 1.61 mg V(V)/g. The experimental kinetic data show the adsorption course according to the pseudo-second order model.

Efficient Vanadate Removal by Mg-Fe-Ti Layered Double Hydroxide

A series of novel layered double hydroxides (Mg-Fe-Ti-LDHs) containing Mg2+, Fe3+ and Ti4+ were prepared. The adsorption performance of Mg-Fe-Ti-LDHs on vanadate in aqueous solution was investigated and the effects of various factors on the adsorption process were examined, including initial vanadate concentration, adsorbent dosage, contact time, solution pH and coexisting ions. A preliminary discussion of the adsorption mechanism of vanadate was also presented. Results show that the adsorption efficiency of vanadate increased with the introduction of Ti4+ into the laminate of LDHs materials. The adsorption capacity of the materials also differed for different anion intercalated layers, and the Mg-Fe-Ti-LDHs with Cl− intercalation showed higher vanadate removal compared to the CO32− intercalated layer. Furthermore, Mg-Fe-Ti-CLDH showed higher vanadate removal compared to pre-calcination. The adsorption experimental data of vanadate on Mg-Fe-Ti-LDHs were consistent with the Langmuir adsorption isotherm model and the adsorption kinetics followed a pseudo-second order kinetic model. The pH of the solution significantly affected the vanadate removal efficiency. Meanwhile, coexisting ions PO43−, SO42− and NO3− exerted a significant influence on vanadate adsorption, the magnitude of the influence was related to the valence state of the coexisting anions. The possible adsorption mechanisms can be attributed to ion exchange and layered ligand exchange processes. The good adsorption capacity of Mg-Fe-Ti-LDHs on vanadate broadens the application area of functional materials of LDHs.

Biosorption of V(V) onto Lantana camara biochar modified by H3PO4: Characteristics, mechanism, and regenerative capacity

Biochar has been widely recognized as an environmentally efficient adsorbent for removing heavy metals. However, considering the weak adsorption performance of the original biochar to the oxygen-containing anion, the adsorption of vanadium by biochar has rarely been investigated. This study proposes that H₃PO₄ activated biochar made from an invasive plant species growing near mines is a novel material to be investigated for V(V) recovery and reuse. As a noxious, invasive plant, Lantana camara L. (LC) has become widely naturalized around the world. Biochar was prepared from LC by pyrolysis at different conditions (200 °C, 350 °C, 500 °C, and 650 °C). The adsorption effect of biochar with and without P pretreatment on V(V) in aqueous solution was compared. The results show that biochar prepared from LC impregnated with H₃PO₄ (MLBC) had the highest adsorption capacity at 500 °C, and the maximal adsorption capacity fitted by Langmuir model was 77.38 mg g^-1, which was considerably higher than that of untreated biochar (LBC, 5.89 mg g^-1). The adsorption procedure was substantially fitted by the Langmuir isotherm and the pseudo-second-order kinetic. Additionally, the interaction of V(V) on MLBC is pH-dependent, and slightly acidic conditions are more favorable for adsorption. The characterization results indicated that electrostatic interaction, complexation reaction, and redox reaction were the primary mechanisms. After three cycles of adsorption, the final maximal adsorption capacity of MLBC remained at 76.03% of that of the virgin sample, demonstrating that MLBC had a recyclable capability to eliminate and restore V(V) from aqueous solutions.