Abstract The formation and evolution of desilication products (DSPs) in synthetic sodium aluminate solution with different reaction temperatures, holding time, CaO additions and carbonate concentrations were investigated based on the Bayer process. The DSPs precipitated at 145 °C and 195 °C are mainly composed of hydrogarnet, tricalcium aluminate hexahydrate and zeolite, and the precipitation sequence is: tricalcium aluminate hexahydrate→hydrogarnet→zeolite. As the desilication temperature increases to 245 °C for 1 h, the ZEO disappears and the HG content reaches 97.8% when the mass ratio of added CaO to SiO2 in solution is 3:1. The SiO2 saturation coefficient of hydrogarnet increases from 0.79 to 1.23 when the desilication temperature rises from 145 °C to 245 °C for 1 h. The crystallinity of various DSPs is enhanced by the reaction temperature, time and CaO addition. The presence of carbonate in sodium aluminate solution promotes the formation of calcium-cancrinite, inhibits the precipitation of hydrogarnet, and decreases the crystallinity and SiO2 saturation coefficients of DSPs. The lattice constants of DSPs increase with the increasing desilication temperature and carbonate concentration.

中文翻译：

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基于拜耳法的CaO-Na2O-Al2O3-SiO2-H2O体系脱硅产物的沉淀

摘要 基于拜耳法研究了不同反应温度、保温时间、CaO添加量和碳酸盐浓度的合成铝酸钠溶液中脱硅产物(DSPs)的形成和演化。145℃和195℃析出的DSPs主要由氢化石榴石、六水铝酸三钙和沸石组成，沉淀顺序为：六水铝酸三钙→氢化石榴石→沸石。当脱硅温度升至 245 °C 1 h 时，当溶液中添加的 CaO 与 SiO2 的质量比为 3:1 时，ZEO 消失，HG 含量达到 97.8%。当脱硅温度从 145 ℃升至 245 ℃ 1 h 时，水石榴石的 SiO2 饱和系数从 0.79 增加到 1.23。反应温度提高了各种 DSP 的结晶度，时间和 CaO 添加量。铝酸钠溶液中碳酸盐的存在促进钙钙质的形成，抑制水石榴石的沉淀，降低DSPs的结晶度和SiO2饱和系数。DSP 的晶格常数随着脱硅温度和碳酸盐浓度的增加而增加。