Xia Min, Ye Chunsong, Pi Kewu, Liu Defu, Gerson Andrea R
School of Power and Mechanical Engineering, Wuhan University, Wuhan, Hubei 430072, China E-mail:
School of Resource and Environmental Engineering, Hubei University of Technology, Wuhan, Hubei 430068, China.
Water Sci Technol. 2017 Nov;76(9-10):2842-2850. doi: 10.2166/wst.2017.452.
Selective removal of Ca and recovery of Mg by precipitation from flue gas desulfurization (FGD) wastewater has been investigated. Thermodynamic analysis of four possible additives, NaCO, NaCO, NaF and NaSO, indicated that both carbonate and oxalate could potentially provide effective separation of Ca via precipitation from Mg in FGD wastewater. However, it was found experimentally that the carbonate system was not as effective as oxalate in this regard. The oxalate system performed considerably better, with Ca removal efficiency of 96% being obtained, with little Mg inclusion at pH 6.0 when the dosage was ×1.4 the stoichiometric requirement. On this basis, the subsequent recovery process for Mg was carried out using NaOH with two-step precipitation. The product was confirmed to be Mg(OH) (using X-ray diffraction and thermo gravimetric analysis) with elemental analysis suggesting a purity of 99.3 wt.%.
研究了通过烟道气脱硫（FGD）废水沉淀法选择性去除钙并回收镁的方法。对四种可能的添加剂Na₂CO₃、Na₂C₂O₄、NaF和Na₂SO₄进行的热力学分析表明，碳酸盐和草酸盐都有可能通过沉淀从FGD废水中的镁中有效分离出钙。然而，实验发现，在这方面碳酸盐体系不如草酸盐有效。草酸盐体系的表现要好得多，当用量为化学计量要求的1.4倍时，在pH 6.0条件下，钙的去除效率达到96%，镁的夹带量很少。在此基础上，采用两步沉淀法用NaOH对镁进行后续回收处理。通过X射线衍射和热重分析确认产物为Mg(OH)₂，元素分析表明纯度为99.3 wt.%。
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