水环境
朱义年,张华,梁延鹏,刘辉利,张学洪.砷酸钙化合物的溶解度及其稳定性随pH值的变化[J].环境科学学报,2005,25(12):1652-1660
砷酸钙化合物的溶解度及其稳定性随pH值的变化
- Dependence of solubility and stability of calcium arsenates on pH value
- 基金项目：国家自然科学基金(No.40263001);教育部科学技术研究重点项目(No.2003-77-03102);广西高校百名中青年学科带头人资助计划(No.2003-97)
- 作者
- 单位
- 朱义年
- 桂林工学院资源与环境工程系, 桂林 541004
- 张华
- 桂林工学院资源与环境工程系, 桂林 541004
- 梁延鹏
- 桂林工学院资源与环境工程系, 桂林 541004
- 刘辉利
- 桂林工学院资源与环境工程系, 桂林 541004
- 张学洪
- 桂林工学院资源与环境工程系, 桂林 541004
- 摘要：通过混合沉淀和溶解实验详细研究了pH值和Ca/As摩尔比对石灰沉淀法处理高浓度含砷废水的影响.沉淀后溶液中的As浓度随pH值的变化趋势与混合液的Ca/As摩尔比有关,在Ca/As=1.50和1.67时,沉淀后溶液中的As浓度在pH=7附近达到最低,然后随pH值的升高而呈现出增大的趋势;在Ca/As=2.00和4.00时,沉淀后溶液中的As浓度随pH值的升高而降低,且2种Ca/As摩尔比条件下的实验结果基本一致.混合沉淀过程中生成的砷酸钙化合物的组成与结构取决于溶液的Ca/As摩尔比和pH值.在低pH值和低Ca/As摩尔比条件下形成的沉淀物要比在高pH值和高Ca/As摩尔比条件下形成的沉淀物的颗粒要大,而且结晶程度要好.在Ca/As摩尔比为1.0～4.0和不同pH值条件下,主要生成Ca3(AsO4)2·3H2O、Ca3(AsO4)2·2.25H2O、Ca5(AsO-4)3OH和Ca4(OH)2(AsO4)2·4H2O,溶度积分别等于10-21.14、10-21.40、10-40.12和10-27.49.
- Abstract：The effect of pHand Ca/As ratio on the lime precipitation of arsenic-containing wastewater was studied in detail by both precipitation and dissolution experiments. For the precipitation under Ca/As=1.5 and 1.67, the residual arsenic concentration reached the lowest value at pH 7.0, and then increased slowly with the increasing pHvalues. The residual arsenic concentration after precipitation under Ca/As=2.0 and 4.0 decreased quickly with the pHincrease. There was no great difference between the experimental results for Ca/As=2.0 and 4.0. The composition and structure of the calcium arsenate compounds, which precipitated from the mixing of As solution with Ca(OH)2 slurry, depended on the pHand the Ca/As molar ratio. The particle size of the solids precipitated at high pHand high Ca/As ratio was much finer than for the low-pHand low-Ca/As precipitated solids. Ca3(AsO4)2·3H2O, Ca3(AsO4)2·2.25H2O, Ca5(AsO4)3OH and (Ca4(OH)2(AsO4)2·4H2O) were identified in the experiment over a wide range of pHand for Ca/As molar ratios between 1.0 and 4.0. Based on the analytical results,their solubility products were calculated as Ksp of 10-21.14, 10-21.40, 10-40.12 and 10-27.49, respectively.
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