Separation and adsorption of V(V) from canadium-containing solution by TOMAC-impregnated resins

A molecular extraction process for vanadium based on tandem selective complexation and precipitation

Recycling vanadium from alternative sources is essential due to its expanding demand, depletion in natural sources, and environmental issues with terrestrial mining. Here, we present a complexation-precipitation method to selectively recover pentavalent vanadium ions, V(V), from complex metal ion mixtures, using an acid-stable metal binding agent, the cyclic imidedioxime, naphthalimidedioxime (H2CIDIII). H2CIDIII showed high extraction capacity and fast binding towards V(V) with crystal structures showing a 1:1 M:L dimer, [V2(O)3(C12H6N3O2)2]2-, 1, and 1:2 M:L non-oxido, [V(C12H6N3O2)2] ̶ complex, 2. Complexation selectivity studies showed only 1 and 2 were anionic, allowing facile separation of the V(V) complexes by pH-controlled precipitation, removing the need for solid support. The tandem complexation-precipitation technique achieved high recovery selectivity for V(V) with a selectivity coefficient above 3 × 105 from synthetic mixed metal solutions and real oil sand tailings. Zebrafish toxicity assay confirmed the non-toxicity of 1 and 2, highlighting H2CIDIII's potential for practical and large-scale V(V) recovery.

Recovery of vanadium and nickel from heavy oil fly ash (HOFA): a critical review

Heavy oil fly ash "HOFA" is the fly ash generated in power stations using heavy oil as fuel. HOFA is considered a hazardous waste because it contains considerable amounts of heavy metals. However, it contains significant amounts of vanadium "V" and nickel "Ni", which are precious metals for manufacturing processes. This paper presents a critical review of various approaches described in the literature for the recovery of V and Ni from HOFA, including processes of leaching, chemical precipitation, solvent extraction, and ion exchange. The optimum operational parameters and their effects on recovery efficiency are discussed. The digestion mixtures of strong mineral acids used for dissolving all metals present in HOFA are also highlighted. The leaching processes of V and Ni use mainly acidic and alkaline solutions. Bioleaching is a promising environmentally friendly approach for the recovery of V and Ni through using appropriate bacteria and fungi. After leaching, V and Ni compounds are recovered and purified using various techniques, including chemical precipitation, solvent extraction, and ion exchange. In most cases, V and Ni are recovered as thermally decomposable compounds that undergo calcination to produce V₂O₅ and NiO. Eventually, V and Ni are recovered as pure oxides in most approaches, but pure metals are obtained in exceptional procedures.

Metakaolin-based geopolymer for mercury removal from model wastewater

Mercury is recognized as a serious hazard, nature bioaccumulative and persistent to the environment. Developing a low-cost, effective, eco-friendly adsorbent for removing mercury constitutes an urgent task. In this study, metakaolin-based geopolymer (MKG) was synthesized and applied to remove mercury from model wastewater by adsorption. The samples were characterized by X-ray fluorescence (XRF), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD) pattern, Fourier transform infrared (FTIR), and scanning electron microscope (SEM). They confirmed the synthesis of geopolymer due to the mass loss (LOI), crystallinity, peak changes, increase in surface area, and pore size. The highest removal efficiency recorded was 65.1%, with a corresponding adsorption capacity of 38.1 mg/g for MKG in 50 mg of dosage, 50 mg/L initial concentration, at a temperature of 25°C, contact time of 5 h and optimal pH of 3. The kinetic studies showed that mercury removal increased with the contact time until equilibrium after an hour. The adsorption equilibrium data were best described by Freundlich, whereas the pseudo-second-order model best fitted the adsorption kinetics. This may be indicative that chemisorption controlled the adsorption process. The stability studies of MKG adsorbent within the four reagents revealed that MKG has good stability in water, followed by 10% HCl, 3M NaCl, and 5% NaOH. In contrast, the desorption revealed the MKG represented the highest desorption efficiency in 10% HCl, followed by 3M NaCl, deionized water and 5% NaOH, respectively. The highest desorption efficiency was 96.83% for 10% HCl, followed by 91.83% for 3M NaCl, 82.55% for H2O, and 50.72% for 5% NaOH. PRACTITIONER POINTS: A low-cost metakaolin-based geopolymer (MKG) was synthesized and applied as an adsorbent for removing Hg(II). The most dominant mechanism involved in the removal process of Hg(II) was chemisorption. The maximum adsorption capacity obtained in this study was 38.1 mg/g. Hg(II) removal is influenced by pH zeta potential and temperature. MKG shows good potential for the effective removal of mercury from modeled wastewater.