New insights into the surface chemical properties of serpentine and flotation of pyrite using xanthomonas campestris as a novel selective serpentine depressant: Experimental and DFT investigation

The flotation separation of pyrite (Py) from serpentine (Spt) was studied using xanthamonas campestris (XC) as a novel Spt depressant. The adsorption of XC onto Spt and Py was observed to decrease with increase in pH attesting to increased repulsion between the negatively charged carboxylate portion of XC and the increased negativity of the mineral surface. However, the polysaccharide adsorption onto Py was less than that onto Spt due to a higher iso-electric point (IEP) of Spt compared to that of Py. Further, theoretical investigations using quantum theory of atoms in molecules (QTAIM) revealed that XC adsorption onto Spt was due to hydrogen bonding (HB), partial and non-covalent interactions, whereas that onto Py was due to partial covalent and non-covalent interactions. Additionally and in general, the adsorption of XC onto the minerals was due to the shift of electrons from the polysaccharide to mineral surface species. Flotation studies conducted at pH 7.8 of Py-Spt (1:1) in presence of 20 g/t, 80 g/t and 60 g/t of sodium tripolyphosphate (SPP), XC and potassium amyl xanthate (PAX) yielded Py grade and separation efficiency of 98.7 % and 97.8 %, respectively, at an economical cost. Therefore, XC is a potential depressant for Spt.