Utilization of Phosphogypsum to Prepare High-Purity CaCO₃ in the NH₄Cl–NH₄OH–CO₂ System

Abstract

High-purity CaCO3 via a facile two-step dissolution–carbonation coprecipitation procedure using NH4Cl, NH4OH, and CO2 with phosphogypsum (PG) as the raw material was successfully produced in the present work. The impact of different experimental parameters on dissolution and carbonation processes was discussed herein. The optimum amount of dissolved CaSO4·2H2O in PG was found to be 18.7 g/L, and the optimum carbonation ratio was found to be 98.22%. The carbonation filtrate could be used up to nine times. Meanwhile, the corresponding reaction efficiency would remain above 50%. Products composed of vaterite and calcite and those composed of pure vaterite and pure calcite were successfully produced. The purity of the product was measured to be 99.8%, and its whiteness was 95.8%. The prepared products met the specifications in the HG/T 2226-2010 Chinese standard. The suggested CaCO3 preparation and PG utilization scheme show promising prospect for applications.

Indirect aqueous carbonation of CaSO4·2H2O with aspartic acid as a recyclable additive

“…Conversely, if the carbonation ltrate containing the sulfate salt and the additive is recycled directly aer removing the CaCO 3 precipitate, as previously reported by Chen et al, 9,11 the content of the sulfate salt increases as the ltrate cycle number increases, inhibiting the dissolution of CaSO 4 $2H 2 O due to the common ion effect. These drawbacks therefore limit the recycling and recovery of the leaching additives, which is a signicant hurdle in the large-scale industrial implementation of the indirect aqueous carbonation process based on the use of BG.…”

“…λ : the reaction efficiency ( ), where m 0 presents the mass of CaCO 3 when the additive was first used, and m N denotes that under different cycle indices. 11 c : additive content, mol L −1 ; LS: liquid-to-solid ratio, mL g −1 ; t : temperature, °C; Q : CO 2 flow rate, mL min −1 ; θ : carbonation reaction time, min.…”

“…Based on the salt and complex effects, researchers have reported several effective leaching additives, such as NaCl, 9 CH 3 COONH 4 , 10 NH 4 Cl, 11 and NaC 6 H 11 O 7 . 12 However, together with the release of Ca 2+ , the SO 4 2− that is leached from CaSO 4 ·2H 2 O can form a byproduct sulfate salt with the cationic component of the added basic medium.…”

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

“…The carbonization has a yield of 90% but has not found any industrial application. Ma J. et al [11] and Chen Q. et al [12] discuss the carbonization process of phosphogypsum with ammonium carbonate. The result is CaCO 3 of very high purity.…”

Study of Semi-Dry High Target Solidification/Stabilization of Harmful Impurities in Phosphogypsum by Modification

“…In recent years, many environmentalists have attached great importance to the resource treatment of PG and have been eager to solve this problem. The current studies on resource utilization of PG are primarily focused on the following aspects: preparation of sulfuric acid and cement [14], construction materials [15], improvement of soil [16], and synthesis of high-strength gypsum [17], CaCO 4 [18], calcium sulfate whiskers [19], agricultural fertilizers [20][21][22], soil conditioners and so on [23][24][25][26]. Especially, much of the work revealed the great opportunities related to the use of PG in different applications.…”