Influence of Impurities on the Process of Obtaining Calcium Carbonate during the Processing of Phosphogypsum

Abstract

The article is devoted to the study of the influence of residual sulfuric and phosphoric acids on the process of processing large-tonnage phosphogypsum (PG) waste into calcium carbonate. In the Russian Federation, about 10 percent of existing phosphogypsum waste is processed into construction materials. Acidic impurities (phosphoric and sulfuric acids) in their composition are an obstacle to the use of phosphogypsum for the production of binders. This study finds that impurities also reduce the chemical activity of phosphogypsum. At the same time, the paper focuses on the potential of phosphogypsum for the production of calcium carbonate. This article investigated the amount of impurities in phosphogypsum. The results show that during automatic washing of phosphogypsum, losses are approximately 30–35 wt. %. It was also found that phosphogypsum by 22% consists of impurities of phosphoric and sulfuric acid. These acids are characteristic waste products of extraction phosphoric acid (EPA) production. By ASTM C471M-20ae1, the content of calcium sulfate dehydrate and hemihydrate before and after washing was determined. A thermodynamic calculation of the proposed interaction of phosphogypsum with carbonates showed that the characteristic reaction is possible. The conversion process of phosphogypsum to get the corresponding calcium carbonate was carried out at 70 °C. Data on the chemical composition of the reaction products, obtained by X-ray fluorescence analysis on a Shimadzu EDX-7000 spectrometer, showed that some reactions proceed incompletely and need the selection of optimal conditions. The potential commercial benefits of processing phosphogypsum by carbonization were defined for products such as calcium carbonate or its derivatives.

Application of the UNIFAC Model for the Low-Sulfur Residue Marine Fuel Asphaltenes Solubility Calculation

“…where k is the cryoscopic constant of benzene (5.12 • C), a is the asphaltene concentration in grams per 1000 g of solvent, ∆T is the freezing point depression. The elemental composition of asphaltenes was determined on a LECO CHN628 analyzer (Leco Corporation, St. Joseph, MI, USA) [50,51], the sulfur content was determined on an XRF-1800 (Shimadzu, Japan) X-ray fluorescence analyzer [52,53]. The oxygen content was calculated by subtraction the total content of other elements from 100%.…”

Complex Formation of Rare-Earth Elements in Carbonate–Alkaline Media

“…The carbonate conversion of phosphogypsum is less demanding on raw materials, while it is possible to process phosphogypsum of any lying state. The potential of phosphorus feedstock for recovery of REE is described in the works [10,11]. REE in red mud are associated with iron minerals [12,13]; thus, the process is more complex.…”

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

“…Pyagai et al [24] studied the waste phosphogypsum from the Phosagro industrial site (Volkhov), which is a gray-white powder with a mass fraction of 60% of the main substance in terms of calcium sulfate. The study found that acidic impurities (phosphoric and sulfuric acids) in the phosphogypsum are an obstacle to its use in the production of building materials.…”