Experimental and theoretical investigations into the surface chemical properties and separation of serpentine from quartz using xanthomonas campestris as a selective flocculant

Abstract

Separation of fine serpentine (SPT) from quartz (QZ) both of d80 close to 20 µm using an eco-friendly microbial exo-polysaccharide, xanthomonas campestris (XCT), as a selective flocculant for SPT was conducted experimentally and substantiated theoretically. The adsorption of XCT onto SPT was observed to decrease with increase in pH, whereas that of QZ was nearly nil beyond pH 2.1. Zeta potential of SPT in presence of XCT decreased with increase in pH further attesting to the adsorption and anionicity of XCT. The FTIR studies confirmed the interaction of XCT with SPT in presence of sodium hexametaphosphate. The nature of intermolecular interactions present in complexes formed on SPT surface was revealed by quantum theory of atoms in molecules to be non-covalent. The electron density difference plot conducted on formed complexes indicated that electrons drifted from XCT to the surface of SPT. Selective flocculation SPT-QZ (1:1) mixture conducted at pH 6 and pH 7.5 in presence of 4 mg/L and 2 mg/L of sodium hexametaphosphate coupled with 100 mg/L of XCT yielded separation efficiency and selectivity ratio of 96.5 % and 71.2, respectively, after three desliming stages. Therefore, XCT is a potential selective flocculant for serpentine.