Adsorption of pentavalent vanadium and hexavalent chromium from vanadium extraction wastewater using modified diatomite

Vanadium extraction from vanadium (V) slag generates wastewater containing a large number of pentavalent vanadium [V (V)] and hexavalent chromium [Cr (VI)], posing environmental and health risks if discharged untreated. This study investigated the use of Fe2SO4 <middle dot> 7H2O-modified diatomite as an adsorbent for removing V (V) and Cr (VI) from vanadium extraction wastewater (VEW). Static adsorption experiments were conducted to assess the adsorption capacity and removal efficiency of modified diatomite under varying conditions of adsorbent dosage, pH, and contact time. The results indicated removal rates of 97.4% for V (V) and 65.8% for Cr (VI) at pH 5, using 3 g of adsorbent dosage over 1440 min. In comparison with unmodified diatomite, the modified version exhibited a 667% increase in V (V) removal and a 531% increase in Cr (VI) removal, indicating significant enhancement in adsorption capacity post-modification. Adsorption capacity decreased with increasing dosage of modified diatomite. Moreover, the adsorbent under acidic conditions demonstrated superior adsorption effectiveness over neutral and alkaline conditions. Furthermore, the kinetics model revealed that adsorption followed Pseudo-second-order and Elovich kinetics, indicating chemisorption and complexation with active functional groups as dominant mechanisms. This study elucidated the effectiveness mechanisms of diatomite modification, paving the way for enhanced V (V) and Cr (VI) removal technologies in industrial wastewater treatment.