Concentrating rare earth elements in brown coal humic acids by mechanochemical treatment

The distribution and enrichment characteristics of rare earth elements between coals and coal ashes from four coal-fired power plants

Coal and coal ash (slag and fly ash) have emerged as important potential sources for rare earth elements (REY). The distribution and enrichment of REY during coal combustion from coal-fired power plants are of great significance for the recovery of REY. In this study, the concentration of REY in coal and coal ash from four coal-fired power plants in China was determined using microwave digestion-inductively coupled plasma mass spectrometry. The distribution and enrichment characteristics of REY in coal and coal ash were studied. The coal ash contains 310-683 μg g-1 of REY, and the proportion of critical REY was greater than 30%, which is higher than the extraction concentration (300 μg g-1) recommended by the United States Department of Energy, indicating significant REY recovery potential. The concentration of REY in coal was positively correlated with ash yield, which could be explained by the fact that REY are mainly distributed in minerals. Coal and coal ash show similar REY distribution patterns, indicating that REY were not fractionated during the coal combustion. In addition, the enrichment coefficient of REY in fly ash was greater than that in slag, which revealed that REY were mainly enriched in fly ash. Therefore, the REY in fly ash has more recycling potential.

Alkaline Extraction of Organomineral Potassium Humate from Coal Mining Waste

Organomineral potassium humate was extracted from coal mining waste from the Lenger deposit (Turkestan region, Kazakhstan) by alkaline extraction using an aqueous solution of potassium hydroxide. The time and temperature of the process were investigated for the degree of extraction and yield of the product. A comprehensive study of the physicochemical properties of the raw material and the resulting production potassium humate was carried out by chemical analysis, scanning electron microscope, energy dispersion, IR-Fourier spectrometric and X-ray diffractographic analyses. The maximum degree of extraction and yield of the product wasachieved at 80 °C and 90 min. Moreover, the experimental data were subjected to kinetic processing, as a result of which it was established that the process of extraction of potassium humate occurs in the external diffusion region.