Research into the process of carbonate conversion of phosphogypsum in the water media

• Main Author: Dmytro Yelatontsev
• Format: Article
• Language: English
• Published: PC Technology Center 2021-07-01
• Series: Technology Audit and Production Reserves
• Subjects: carbonate conversion phosphogypsum; sodium hydroxide; calcium hydroxide; carbon dioxide; carbonization; x-ray phase analysis; mass spectrometry; conversion temperature; mineralogical composition
• Online Access: http://journals.uran.ua/tarp/article/view/235243
• ISSN: 2664-9969; 2706-5448

For a long time, the problem of phosphogypsum disposal was not given due attention, which led to the accumulation of huge reserves of this environmentally hazardous waste. Transportation of phosphogypsum in dumps and its storage requires significant capital investment and operating costs, as well as the allocation of large land areas. The storage of phosphogypsum harms the environment, as it leads to the entry of significant amounts of toxic substances into groundwater and the atmosphere. The object of the study was phosphogypsum, which is formed during the production of phosphoric acid from apatites and phosphorites. To date, numerous studies have focused on finding effective ways to use phosphogypsum, but its composition usually limits its reuse. The research aims to study the scientific prerequisites for creating an effective control scheme for phosphogypsum by converting it to calcium carbonate. For this purpose, the chemical composition and technological parameters of phosphogypsum conversion from the dumps of «Dnipro Mineral Fertilizer Plant» (Kamianske, Ukraine) were studied. The proposed conversion method involved a reaction between phosphogypsum and aqueous NaOH solution to form Ca(OH)2, which was converted to CaCO3 by carbonization in a CO2 stream. The influence of temperature on the conversion of phosphogypsum into Ca(OH)2 has been established. The conversion was investigated at 25 °C, 40 °C, and 70 °C for 3 hours. It was found that at the first stage of the process the impurities contained in phosphogypsum were transferred to the precipitate of Ca(OH)2. As a result of carbonization, low-quality CaCO3 was obtained, which contained more than 10% of impurities. Increasing the duration of carbonization to 1 hour allowed to obtain CaCO3 with content of Ca(OH)2<4 %. The results of the study show that the method of carbonate conversion of phosphogypsum requires further optimization of technological parameters to improve the purity of the finished product.