Scaling up the Mechanochemical Technology for Producing Materials Enriched in Humic Acids

Abstract

Abstract Mechanochemical treatment is widely used in industry as it allows one to reduce the number of processing stages, either reduce or completely eliminate the use of solvents, automate the technology and ensure its mobility. Energy input is an important parameter of mechanochemical treatment. In this study, the technology of mechanochemical oxidation of brown coal was scaled up using the planetary mills of AGO-2 and APF types, as well as K-7 and CEM-20 flow-type vibrocentrifugal mills. The technology of mechanochemical oxidation of brown coal makes it possible to increase the availability of humic acids in brown coal and the content of oxygen-bearing groups capable of complexation, as well as to improve sorption characteristics of the resulting product. Materials enriched in humic acids can be used as heavy metal sorbents in water bodies and as agents for soil amelioration. The rotor speed of 1400 rpm and the feed rates of 15 kg/h and 1.8 kg/h for CEM-20 and for K-7 vibrocentrifugal mills, respectively, are the optimal modes from the point of view of chemical and economic efficiency. These modes increase the yields of alkali-soluble and water-soluble humic acids from 23 to 59 % and from <1 to 7%, respectively, which corresponds to the values reached using the laboratory-scale equipment.