FEATURES OF SYNTHESIS OF INORGANIC LUMINESCENT MATERIAL FROM PHOSPHOGYPSUM

The paper discusses technological methods for obtaining a luminescent material from phosphogypsum. The obtained materials were characterized using X-ray phase analysis, X-ray fluorescence analysis, and electron microscopy. The elemental composition of the samples was determined using a laboratory micro-fluorimeter. In the course of the study, the technological conditions for converting the main part of phosphogypsum into a luminescent material based on calcium sulfide were established. It is shown that the process of obtaining luminescent CaS consists of dehydration stages: the initial stage, carried out at a temperature of 373 K to remove physically bound water, and the final stage, at a temperature of 1073 K – to remove crystallization water, as well as the stage of phosphogypsum reduced at a temperature of 1173 K for 0.5 h. An environmentally friendly material-sucrose-is considered as a reducing agent. It is shown that in the case of changing the technological modes of reduction the luminescent material cannot be obtained. Conducting the reduction process at a temperature of 773 K is accompanied by obtaining a sample contaminated with products of incomplete decomposition of the organic component of the charge. In this case, the sample does not contain calcium sulfide. Under prolonged isothermal exposure at a temperature of 1173 K, repeated oxidation of samples with loss of luminescence ability was observed. Optimal technological modes for obtaining materials with phosphor properties are formulated. According to the results of X-ray phase analysis, samples that do not show luminescence capacity contain calcium sulfate as the main phase. Samples-phosphors consist of a mixture of calcium sulfate and sulfide. Results obtained open up wide opportunities for involving in the re-processing of production waste to obtain cheap products in demand.