Separation of high concentration V(V) and Cr(VI) by amorphous hydrous zirconium oxide with high adsorption capacity and selectivity

The challenge of separating and recovering V(V) and Cr(VI) from wastewater is critical for environmental protection and industrial productivity due to the chemical similarities. In this study, a novel zirconium-based adsorbent with superior adsorption performance and selectivity was synthesized using the Sol-Gel method, with a specific surface area of up to 265.3 m 2 /g. The maximum adsorption capacities of V(V) and Cr(VI) were 222 and 123 mg/g, respectively. The adsorption process followed the Langmuir isothermal adsorption and the pseudo-second-order kinetic model. The adsorption mechanism was thoroughly investigated confirming that the adsorption of V(V) and Cr(VI) on amorphous hydrous ZrO 2 (AHZOs) is chemisorption. At a pH of 3, the values of ΔG 0 (−46.8 kJ/mol) and E ads (−5.67 eV) for the main existing form H 3 V 10 O 28 3- on AHZOs are lower than those for the main existing form HCrO 4 - . V(V) replaced the adsorbed Cr(VI) during competitive adsorption to achieve selective adsorption of V(V) with a separation coefficient as high as 3142. The adsorption capacity of V(V) remains above 105 mg/g after five cycles. After adsorption, the purity of Cr(VI) can be increased to above 99.5 %, and a solution of V(V) with a purity higher than 99.25 % can be obtained after desorption. The use of 3 g/L and 100 g/L adsorbent can decrease the single V(V) and Cr(VI) to 1.618 mg/L and 0.36 mg/L, respectively, and meet the emission standards.