Biologically removing vanadium(V) from groundwater by agricultural biomass

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.

Sustainable Selective Recovery of Sulfuric Acid and Vanadium from Acidic Wastewater with Two-Step Solvent Extraction

A two-stage extraction process was proposed to recover sulfuric acid and vanadium from simulated acid solution and titanium dioxide waste acid (TDWA). Some extractants were compared and studied, in which the enthalpy changes (ΔH) of the extraction process and the extracted complex were analyzed by using thermodynamics. The microscopic characteristics of the loaded organic phase were compared and investigated by infrared spectroscopy (FT-IR), where the extraction mechanism was described. The extraction efficiency of sulfuric acid was more than 99% by three-stage countercurrent extraction with 60% triisooctylamine (TEHA) and 35% N-pentanol, in which ΔH was -61.31 kJ/mol and the extracted complex of H2SO4·TEHA·2-N-pentanol was obtained. The extraction efficiency of vanadium was above 98% by using 20% bis-2-ethylhexyl phosphate (P507) and 80% sulfonated kerosene, where ΔH was 14.69 kJ/mol and the extracted complex of VO·2A (vanadium as VO2+ and P507 as HA) was obtained. The stripping efficiencies of sulfuric acid and vanadium were more than 90% and 98%, respectively. The extraction effect of used organic phase after regeneration was equivalent to that of the new organic phase with cycle numbers of less than 10. The real waste acid of TDWA was operated to extract and separate sulfuric acid and vanadium with the same parameters, in which the characteristics of high extraction efficiency and good selectivity were obtained. The technique may provide a new thinking for the separation and recovery of valuable components from TDWA.

Performance of a continuous flow reactor on bio-reducing vanadium with straw

Vanadium (V) in groundwater could cause a serious threat to the environment and health. Continuous flow reactors were applied to reduce V(V) with straw being a solid carbon. The reduced efficiency of V(V) in the reactor with straw and inoculated sludge reached to 71.8%-99.9% for two months' operation (after 44 d). However, a long-term operation with only straw was not satisfied, achieving the reduced efficiency of 39.2-66.6%. The SEM images clearly revealed some traces of straw surface by utilized by microbes, which implied that microbes had a stronger capacity to hydrolyze straw. The introducing external microbes were essential to achieve a better bio-reduction performance on V(V). Treponema (5.3%) with metal reduction ability and Prevotellaceae (3.3%) able to specifically degrade complex plant-derived polysaccharides were found to be dominant in the microbial community. Utilizing agricultural biomass can save a lot of normal carbon like acetate, which is of benefit for carbon emissions.

Performance and Enhancement of Various Fillers Guiding Vanadium (V) Bioremediation

Bioremediation of vanadium (V) pollution in groundwater is an emerging topic. However, knowledge of V in a biogeochemical process is limited and long-term effective removal methods are lacking. V(V) remediation processes by various kinds of auxiliary fillers (maifanite-1, maifanite-2, volcanic rock, green zeolite and ceramsite), agricultural biomass and microbial enhancing were explored in this study. In tests without inocula, the V(V) removal efficiencies of ceramsite (inert filler) and maifanite-2 (active filler) were 84.9% and 60.5%, respectively. When inoculated with anaerobic sludge, 99.9% of V(V) could be removed with the synergistic performance of straw and maifanite-2. TOC (Total Organic Carbon), trace elements and three-dimensional fluorescence analyses confirmed that maifanite-2 was the most suitable among various fillers in biological V(V) removal systems with straw. This study provides a collaborative method (adsorption-biology) by using straw with maifanite-2 in V(V)-contaminated groundwater. The knowledge gained in this study will help develop permeable reactive barrier technology to repair polluted groundwater to put forward a reasonable, effective and sustainable environmental treatment strategy.

Synchronous microbial V(V) reduction and denitrification using corn straw as the sole carbon source

The coexistence of nitrate and V(V) in groundwater aquifers poses potential threats to ecological environment and public health. However, much remains to be elucidated about how the complex microbial community coupled nitrate and V(V) simultaneous bio-reduction with carbon source oxidation. For the first time, it was demonstrated that denitrification and V(V) bio-reduction occur by using corn straw as the sole carbon and energy source. Corn straw was proved to have efficient denitrification and V(V) bio-reduction performance in various environments, especially at V(V) concentrations of 100 mg/L for optimal V(V) reduction rate (19.25 mg/L·d) and at pH of 11 with the best nitrate reduction rate (3.12 d^-1). In addition, an interesting phenomenon was found that the release of V(V) occurred when the carbon source was insufficient and the competitive electron acceptor (NO₃^--N) existed. Metagenomic analysis showed that the addition of corn straw increased the abundance of genes related to metal resistance, cytochrome and dimethyl sulfoxide, and increased the abundance of glycolytic process, which may play a vital role in facilitating the reduction of V(V). These findings can provide basic suggestions for improving the mechanism of V(V) reduction pathway and provide guidance for the remediation of groundwater polluted by nitrate and V(V).

Removing miscellaneous heavy metals by all-in-one ion exchange-nanofiltration membrane

The composition of wastewater containing heavy metal mixtures is often complex and poses a serious threat to human and environmental health. Effective removal of a variety of heavy metal ions with a single technology is challenging, and the conventional split integrated technologies require multi-step processing and a massive footprint. For the first time, we achieve hierarchically integrating ion exchange and nanofiltration into all-in-one "iNF" membranes. The iNF membrane has a hierarchical structure with an interfacial polymerization layer and an ion exchange layer, which can achieve highly efficient indiscriminate heavy metal ion removal, overcoming the defect that traditional nanofiltration membranes can only remove single metal cations or oxyanions. The ion exchange layer can remove heavy metal ions through sulfonic acid groups and quaternary amine groups. In addition, the ion exchange layer can be regenerated by electro-deionization, which is meaningful for sustainable membrane usage. This facile, scalable, and compact integrated process shows outstanding potential and universal applicability in complex wastewater treatment.

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.