Efficient detoxification and removal of vanadium from water by synchronous adsorption and reduction using polyaniline-modified layered double hydroxides

With industry development, water contaminated with vanadium(V) has attracted increasing attention. Various adsorbents have been used to remove V(V); however, reducing V(V) to V(III) or V(IV) with low solubility and toxicity remains a challenge. Herein, a novel layered double hydroxide loading with polyaniline composites (PANI-LDHs) adsorbent was prepared to facilitate V(V) detoxification and elimination. We examined the physicochemical characteristics and confirmed the successful formation of the composite. Some key experimental parameters were evaluated in detail for their potential impact on V(V) removal. The calculated maximum adsorption capacity was 222.22 mg/L with a dosage of only 0.3 g/L under 318 K, which was higher than other adsorbents. More importantly, about 80 % of the absorbed V(V) was reduced and detoxified by reductive nitrogen-containing groups in PANI. In addition, the PANI-LDHs can effectively resist the interference of various coexisting ions. The excellent V(V) removal performance is mainly attributed to the high stability of the inorganic skeleton (LDH) and the high chemical activity of PANI. Dynamics and thermodynamic analysis were also used to study the V(V) adsorption behavior. Finally, the mechanism study suggested that V(V) anions were adsorbed onto the surface of PANI-LDHs via electrostatic attraction or the H-bonding. The adsorbed V(V) was subsequently reduced and immobilized to V(IV) and V(III) oxides by nitrogen-containing groups in PANI, thus achieving the detoxification and removal of V(V). The combination of adsorption and detoxification properties, high adsorption capacity, and good selectivity make PANI-LDHs an ideal candidate for V(V)-containing wastewater treatment.