De Beer, MorrisDoucet, FJMaree, JPLiebenberg, L2016-02-232016-02-232015-08De Beer, M., Doucet, F.J., Maree, J.P. and Liebenberg, L. 2015. Synthesis of high-purity precipitated calcium carbonate during the process of recovery of elemental sulphur from gypsum waste. Waste Management, vol. 46, pp 619-6270956-053Xhttp://ac.els-cdn.com/S0956053X1530091X/1-s2.0-S0956053X1530091X-main.pdf?_tid=e2fa876e-d623-11e5-a337-00000aacb360&acdnat=1455788712_1d130e8e7313668fa7ffac824b506945http://hdl.handle.net/10204/8395Copyright: 2016 Elsevier. Due to copyright restrictions, the attached PDF file only contains the abstract of the full text item. For access to the full text item, please consult the publisher's website. The definitive version of the work is published in the Waste Management, vol. 46, pp 619-627We recently showed that the production of elemental sulphur and calcium carbonate (CaCO3) from gypsum waste by thermally reducing the waste into calcium sulphide (CaS) followed by its direct aqueous carbonation yielded low-grade carbonate products (i.e. <90 mass% as CaCO3). In this study, we used the insight gained from our previous work and developed an indirect aqueous CaS carbonation process for the production of high-grade CaCO3 (i.e. >99 mass% as CaCO3) or precipitated calcium carbonate (PCC). The process used an acid gas (H2S) to improve the aqueous dissolution of CaS, which is otherwise poorly soluble. The carbonate product was primarily calcite (99.5%) with traces of quartz (0.5%). Calcite was the only CaCO3 polymorph obtained; no vaterite or aragonite was detected. The product was made up of micron-size particles, which were further characterised by XRD, TGA, SEM, BET and true density. Results showed that about 0.37 ton of high-grade PCC can be produced from 1.0 ton of gypsum waste, and generates about 0.19 ton of residue, a reduction of 80% from original waste gypsum mass to mass of residue that needs to be discarded off. The use of gypsum waste as primary material in replacement of mined limestone for the production of PPC could alleviate waste disposal problems, along with converting significant volumes of waste materials into marketable commodities.enHigh-purityCalcium carbonateCaco(sub3)Gypsum wasteIndirect carbonationPrecipitated calcium carbonateCalcium sulphidePrecipitated calcium carbonateCalcium sulphideValorisationArticleDe Beer, M., Doucet, F., Maree, J., & Liebenberg, L. (2015). Synthesis of high-purity precipitated calcium carbonate during the process of recovery of elemental sulphur from gypsum waste. http://hdl.handle.net/10204/8395De Beer, Morris, FJ Doucet, JP Maree, and L Liebenberg "Synthesis of high-purity precipitated calcium carbonate during the process of recovery of elemental sulphur from gypsum waste." (2015) http://hdl.handle.net/10204/8395De Beer M, Doucet F, Maree J, Liebenberg L. Synthesis of high-purity precipitated calcium carbonate during the process of recovery of elemental sulphur from gypsum waste. 2015; http://hdl.handle.net/10204/8395.TY - Article AU - De Beer, Morris AU - Doucet, FJ AU - Maree, JP AU - Liebenberg, L AB - We recently showed that the production of elemental sulphur and calcium carbonate (CaCO3) from gypsum waste by thermally reducing the waste into calcium sulphide (CaS) followed by its direct aqueous carbonation yielded low-grade carbonate products (i.e. <90 mass% as CaCO3). In this study, we used the insight gained from our previous work and developed an indirect aqueous CaS carbonation process for the production of high-grade CaCO3 (i.e. >99 mass% as CaCO3) or precipitated calcium carbonate (PCC). The process used an acid gas (H2S) to improve the aqueous dissolution of CaS, which is otherwise poorly soluble. The carbonate product was primarily calcite (99.5%) with traces of quartz (0.5%). Calcite was the only CaCO3 polymorph obtained; no vaterite or aragonite was detected. The product was made up of micron-size particles, which were further characterised by XRD, TGA, SEM, BET and true density. Results showed that about 0.37 ton of high-grade PCC can be produced from 1.0 ton of gypsum waste, and generates about 0.19 ton of residue, a reduction of 80% from original waste gypsum mass to mass of residue that needs to be discarded off. The use of gypsum waste as primary material in replacement of mined limestone for the production of PPC could alleviate waste disposal problems, along with converting significant volumes of waste materials into marketable commodities. DA - 2015-08 DB - ResearchSpace DP - CSIR KW - High-purity KW - Calcium carbonate KW - Caco(sub3) KW - Gypsum waste KW - Indirect carbonation KW - Precipitated calcium carbonate KW - Calcium sulphide KW - Precipitated calcium carbonate KW - Calcium sulphide KW - Valorisation LK - https://researchspace.csir.co.za PY - 2015 SM - 0956-053X T1 - Synthesis of high-purity precipitated calcium carbonate during the process of recovery of elemental sulphur from gypsum waste TI - Synthesis of high-purity precipitated calcium carbonate during the process of recovery of elemental sulphur from gypsum waste UR - http://hdl.handle.net/10204/8395 ER -