Green desorption combined with peptization technology for disposing of Cr(VI)-V(V)-containing hazardous aluminum waste to prepare high-valued pseudo-boehmite

Abstract

Cr(VI)-containing aluminum residues are inevitable industrial hazardous waste in the chromate industry. To reduce and utilize these residues, a combined desorption and peptization technology for disposing of Cr(VI)-V(V)-containing boehmite hazardous waste (γ-AlOOH-Cr-V) with NaOH solutions was proposed, which realized the removal of V(V) and Cr(VI) effectively and the improvement of peptization index (PI) of obtained pseudo-boehmite (PB) synergistically. The results showed that PB with high PI (98.1%) and low content of V(V) (0.0656%) and Cr(VI) (0.0018%) could be achieved by desorbing the γ-AlOOH-Cr-V, while the surface area and pore volume would be decreased during desorption with the increase of NaOH concentration. Besides the leaching toxicity of Cr(VI) of obtained PB of 0.09 mg/L was extremely lower than that of the standard of hazardous waste. It was noted that the evolution of structural hydroxyl groups governed the improvement of peptization performance. DFT results showed that proper interlayer water content was beneficial to the adsorption of hydroxyl ions on the structural hydroxyl groups of PB. This work not only reduced the emission of Cr(VI)-V(V)containing hazardous waste, but also paved the way for the high-valued utilization of co-associated aluminum and vanadium resources in chromite.