Insights into the changes in the surface properties of goethite with Ni in the lattice in the presence of salicylhydroxamic acid: Experimental and density functional theory studies

Comparative experiments and theoretical analysis of the surface chemistry changes of goethite (GT) and goethite containing Ni (GTN) in the lattice in the presence of salicylhydroxamic acid (SA) were performed. It was revealed that in the presence of 100 g·t⁻¹ of SA, the flotation recovery of GTN and GT increased with increasing pH, achieving a maximum recovery of 98.9% for both minerals at pH 8.3 and decreasing beyond that pH, with GTN having a slightly higher recovery than GT, except at pH 8.3. This was further confirmed by the higher complexation energies of GTN⋯SA (−883.87 kJ·mol⁻¹) compared with GT⋯SA (−604.23 kJ·mol⁻¹) resulting from covalent, closed-shell, and conventional hydrogen bonding. The higher adsorption of SA onto GTN relative to GT was due to the formation of a π-hole in GTN, thereby promoting a higher interaction of the collector with the mineral. Thus, the presence of Ni in the GT lattice improves and decreases the adsorption and desorption of SA onto and from the mineral, respectively, compared with those onto and from GT.