Mineralogical and chemical characterization of DD3 kaolin from the east of Algeria

Abstract

The mineralogical and chemical characteristics, based on X-ray diffraction (XRD) and scan-ning electron microscopy, of a kaolin known as DD3, from eastern Algeria were examined in the present study. The results showed that kaolin DD3 has an alumina content of 39%. The SiO2/Al2O3molar ratio of 2.14 is close to that of a pure halloysite. The hematite concentration is relatively large and the flux oxides ratios remain as acceptable impurities. Microscopic observations showed a predominant tubular halloysite phase, flattened hexagonal platelets correspond-ing to the presence of kaolinite and its polymorphs (nacrite, dickite), and hydrated alumina. The SiO2/Al2O3molar ratio and tubular DD3 suggest possible uses in technical ceramics and nanotechnology applications. Analysis by XRD revealed the presence of many phases. Thermal treatment at 450 ◦ C and chemical treatment with HCl confirmed the presence of halloysite. The inclusion in the clay of organic molecules (dimethylsulfoxide (DMSO), DMF, and diluted glycerol) showed that the DMSO led to expansion of the inter-planar distance. The intercalation by DMSO molecules resulted in a shift of the basal peak from 10 to 11.02˚ A and partial displacement of the peak from 3.35 to 3.65˚ A. These two peaks are characteristic of halloysite. The presence of residual nacrite was also confirmed by the shift of the peak observed at 3.35˚ A. A full analysis of the XRD patterns using the Match software, based on these results, showed that the DD3 clay consists of >60% halloysite