STUDY OF THE PROCESS OF NITRATIC ACID PROCESSING OF PHOSPHOGYPSUM TO OBTAIN A CONCENTRATE OF RARE–EARTH ELEMENTS

Abstract

Investigate the process of extraction of rare earth elements from phosphogypsum by its interaction with nitric acid, concentration 25, 30 and 35%, at a ratio of "phosphogypsum: acid" 1: 2 and a temperature of 70⁰C to obtain purified calcium sulfate. Regularities of the process of extraction of concentrate of rare earth elements from phosphogypsum by acid leaching are obtained. Experimental studies were performed using the titrimetric method using Trilon B to determine the concentration of rare earth elements in the obtained filtrates. A review of scientific and technical literature in the field of promising methods of processing phosphogypsum. The most alternative method of processing phosphogypsum is to obtain rare earth elements by acid leaching, which is provided by the use of mineral acids. Based on the obtained data, it was found that when the acid concentration increases from 25 to 35%, the content of rare earth elements (REE) in the filtrates of the samples increases from 0.21 to 1.68 g/dm³, respectively. It was found that the degree of extraction of REE concentrate from phosphogypsum is highest at an acid concentration of 25% and is 22.8%, and with increasing concentration of HNO₃, it decreases by almost 2.5 times. The optimal concentration of the nitric acid solution was determined, which is 25% and interacts with phosphogypsum for the subsequent extraction of the precipitate of rare earth elements.The optimal temperature of nitric acid processing of phosphogypsum, which is 70 ⁰C, was revealed. Regularities of the process of extraction of concentrate of rare earth elements from phosphogypsum by acid leaching are obtained.The use of nitric acid for the production of rare earth elements from phosphogypsum and for the production of purified phosphogypsum sediment from soluble impurities scientifically substantiated. The content of rare earth elements in the filtrate was determined at various acid concentrations. The efficiency of sediment removal of rare earth elements from phosphogypsum by interaction with nitric acid at a concentration of 25, 30 and 35%, respectively, was established. Purified phosphogypsum can then be used to produce gypsum binder in the construction industry and in fertilizer technology in agriculture. Concentrate of rare earth elements can be used in medicine, metallurgy and other industries with the selection of individual elements and in general.