PNNL

Abstract

Boehmite (?-AlOOH) was synthesized to selectively adsorb V(V) from K2CrO4-KVO3-H2O solutions with highly concentrated Cr(VI) and low concentration V(V). The synthesized ?-AlOOH has a BET surface area of 433.2 m2/g and an average pore size of 3.5 nm. It possesses a maximum adsorption capacity of V(V) of 1.53 mmol/g from K2CrO4-KVO3-H2O solutions. The adsorption of V(V) onto ?-AlOOH follows the Langmuir isotherm model and pseudo-second-order kinetics equation by forming innersphere complexes while the Cr(VI) adsorption forms both inner-sphere and outer-sphere chromate complexes depending on solution pH. The ?-AlOOH was further synthesized in situ by adding HNO3 into the K2CrO4-KAlO2- KVO3-H2O solutions and then used for synchronous adsorption of V(V) and Cr(VI), resulting in increased adsorption capacity of V(V) of 2.88 mmol/g and decreased adsorption capacity of Cr(VI) to 0.073 mmol/g, respectively. In the latter process, adsorption pH values were adjustable, and adsorption reached equilibrium instantaneously, supporting a novel in situ synthesis and adsorption integration strategy with adjustable surface charge of adsorbent and disappearance of diffusion effect.