Production Waste Management: Qualitative and Quantitative Characteristics and the Calculation of the Hazard Class of Phosphogypsum

Abstract

Phosphogypsum (PG: CaSO4·2H2O) is a waste product (or by-product) from the production of phosphoric acid, the main component in the production of concentrated simple and complex fertilizers. The world production of phosphogypsum exceeds 200 million tons per year. PG discharged into water bodies (seas, rivers) or disposed of in land dumps may contain elements (including heavy metals and radionuclides) in forms and concentrations that are toxic to ecosystems and human health, which raises concerns about its impact on the environment. The concentrations of these elements vary depending on the region where the raw material is mined and the process used to produce phosphoric acid. Given the significant volumes of phosphogypsum formed, an urgent problem is not only the development of methods for its disposal, but also a special, specific control over its composition after the release of PG and during its use for removal, transportation, and storage in dumps and sludge storages. This article presents the results of comprehensive studies on the determination of the chemical and mineralogical composition of by-products from an experimental plant for the processing of phosphate raw materials of the designed chemical complex of the EuroChem-Karatau company (Republic of Kazakhstan). Based on the conducted studies, it was established that, in terms of the total toxicity index, the studied wastes belong to the fourth hazard class (low-hazardous) with the possibility of processing for the purpose of their further use.