Removal of fatty acid by natural and modified bentonites: elucidation of adsorption mechanism

Abstract

In contemporary society, water plays an important role, but some developmental activities produce extremely high amounts of effluents. A good example is the mining industry, wherein water is critical in practically all mineral processing processes. The aim of the present study was to compare the efficiency of natural and treated bentonites as adsorbents to remove fatty acid collectors, a wastewater from of phosphate minerals flotation process. Computational chemistry tools were used to elucidate the adsorption mechanisms. Two types of natural bentonite, NB and NB2, and NB bentonite modified with the surfactant CTAB (hexadecyltrimethylammonium bromide) were studied. The bentonites were characterized by infrared spectroscopy, X-ray diffraction, X-ray fluorescence, N2 adsorption/desorption and zeta potential analysis. The characterization of this material revealed properties favorable to adsorption. NB2 showed the highest yield in collector removal. Modified material was found to be more efficient in adsorption than the starting material. Theoretical studies were performed using computational chemistry tools, and the results showed that CTAB inserted on the NB surface served as an adsorption site for the collector, promoting intermolecular interactions between adsorbate and adsorbent.