Quantitative phase analysis method of palygorskite based on XRD orientational sample analysis and Rietveld full spectrum fitting

Abstract

Palygorskite is a kind of water-rich magnesium aluminosilicate mineral with a chain-layered structure. Due to the difference in forming environment, the phase composition of palygorskite clay is various, and chemical compositions of palygorskite of different origins are also significantly different, which leads to a great difference in its application performance. Due to the coexistence of various types of layered and chain-layered minerals, conducting quantitative phase analysis of palygorskite raw ore becomes highly challenging. This significantly restricts the development and utilization of palygorskite. Herein, a new scheme is proposed to solve this problem by combining Rietveld full spectrum fitting based on the XRD patterns from internal standard method and orientational sample analysis. The new scheme was applied to the quantitative phase analysis of palygorskite raw ores from Mingguang, Xuyi, and Linze, three of the most representative places of origin in China. Not only the exact content of palygorskite and other crystalline phases in the raw ore, but also the content of mixed-layer minerals, and amorphous phase in the raw ore were obtained. The contents of palygorskite, quartz, illite-smectite mixed-layer minerals, and amorphous in the raw ore of Mingguang were 70.81%, 6.43%, 18.81%, and 3.98%, respectively; the contents of palygorskite, quartz, calcite, illite-smectite mixed-layer minerals in the raw ore of Xuyi were 36.08%, 16.18%, 27.06%, 18.04%, and 2.64%, respectively; the contents of palygorskite, quartz, illite-smectite mixed-layer minerals, calcite, illite, gypsum, feldspar, dolomite, microcline and amorphous in the raw ore of Linze were 10.11%, 34.82%, 5.77%, 1.07%, 5.57%, 8.06%, 12.38%, 17.05%, 2.21%, and 2.96%, respectively.