On the Mechanism of Sodic Removal from Bauxite Residue and Bauxite Desilication Products (BDP) Using Acetic Acid

摘要

Bauxite desilication products (BDPs) are fundamental causes of persistent alkalinity and salinity in bauxite residue. Previous studies have shown that significant amounts of acetic acid and Na+ were detected in the pore water of organic matter-amended and bacteria-regulated bauxite residue, implying the capability of acetic acid to alleviate the long-term residual alkalinity and salinity of bauxite residue. The present study aims to establish a fundamental understanding of the bauxite residue/BDP weathering mechanism using acetic acid as a case model of microbial-derived low-molecular-weight soluble organics. Large amounts of Na+ were released into the solution in treated bauxite residue, implying enhanced desalination of bauxite residue/BDP by acetic acid. Attenuated total reflectance-Fourier transform infrared spectroscopy, Raman spectroscopy, and nuclear magnetic resonance spectroscopy indicated the adsorption of acetate on the surface of BDP, which caused slight deformation of BDP's cages and thus made encaged Na+ exchange easily with other cations. This mechanism of organic acid-mediated Na+ exchange may provide the key to unlocking the barrier of alkaline mineral weathering and subsequent development of soil-like properties for sustainable plant colonization.