Comparison of two purification methods of Algerian bentonite: chemical, mineralogical and physicochemical properties

Abstract

The aim of this work is to evaluate the efficiency of two methods of purification on Algerian bentonite clay. The first method was performed by centrifugation treatment, using sodium hexametaphosphate (NaPO3)6 as a dispersing agent. The second method involves a chemical purification with NaCl, followed by sedimentation technique. The study concerns mineralogical, chemical, structural aspects and a series of physical testing. The results have shown that the raw bentonite (RBN) contain (~ 59%) of montmorillonite, illite (~ 5) and (~26%) of quartz, and feldspar (orthoclase + albite), with 5% of calcite. In the purified state by NaCl (RBN-2), the mineralogical and physicochemical properties including cation exchange capacity and specific surface area are higher than the purified samples by physical beneficiation (by centrifugation - RBN-1). Moreover, the treatment with NaCl increased the montmorillonite content of the bentonite from 56 % to 100%. The quartz impurities were totally removed in RBN-2, whereas impurities (quartz + feldspar) were still observed by the X-ray diffraction (XRD). Finally, the results obtained from the morphological, mineralogical and chemical characterization confirm that the bentonite RBN -2 was more effective , and it has promise as an engineering material compared to the RBN and RBN-1, indicating its possible application in various industrial applications.