Dissolution and solubility of the synthetic natroalunite and the arsenic-incorporated natroalunite at pH of 2.00-5.60 and 25-45°C
Dissolution and solubility of the synthetic natroalunite and the arsenic-incorporated natroalunite at pH of 2.00-5.60 and 25-45°C
复制标题
合成钠明矾石和掺砷钠明矾石在pH 2.00-5.60和25-45℃下的溶解度和溶解度
DOI：
10.1155/2019/9568360
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发表时间：
2019
影响因子：
3
通讯作者：
Shen Tang
中科院分区：
文献类型：
--
作者：
Yinian Zhu;Huiling Xuan;Yanpeng Liang;Qiming Yan;Zongqiang Zhu;Zhangnan Jiang;Lihao Zhang;Huili Liu;Shen Tang
砷对大多数生物体都是非常有害的。含砷化合物的溶解度数据在地球科学和环境科学中具有重要意义。已经提出了掺入砷的钠明矾石沉淀来消除水中的砷，用于工业实践和污染地区的修复。不幸的是，只有很少的工作已经取得了部分砷掺入钠明矾石和钠明矾石和砷掺入钠明矾石的热力学数据现在仍然缺乏。此外，砷掺入钠明矾石的溶解机制从未被研究过。本文研究了合成钠明矾石[Na0.93（H3 O）0.61Al2.82（SO 4）2（OH）6]和合成含砷钠明矾石[Na0.88（H3 O）2.44Al2.35（AsO 4）0.38（SO 4）1.62（OH）6]在25 ℃、35 ℃、35 ℃、45 ℃、45 ℃、65 ℃、75 ℃、75 ℃、85 ℃、85 ℃、85 ℃下的溶解行为，并对钠明矾石的溶解机理进行了探讨。在HNO 3溶液（pH值为2.00和4.00）和纯水中对45°C下的反应进行了实验研究。表征证实固体在溶解后没有显示可识别的变化。所有溶解都经历了pH值的变化，这是由H3 O +/OH-离子的大量消耗（通常在反应开始时）引起的。在H3 O+介质中的溶解被证明在短的开始时间内接近化学计量，并且溶解的Na+、Al 3+、SO 42-和AsO 43-浓度根据初始固体是化学计量的，然后似乎是非化学计量的，Na/SO 4摩尔比高于化学计量，Al/SO 4和AsO 4/SO 4摩尔比低于化学计量，直到实验结束，表明组分从固体向溶液的释放顺序为Na+（H3 O+）> SO 42-> AsO 43-> Al 3+。从初始pH 2.00和25 ℃条件下的实验结果来看，溶度积[Ksp]和生成吉布斯自由能[]计算为10−81.02±0.33 kJ/10−81.04± 0.27和−4713 ± 2至−4714 ± 1 kJ/钠明矾石和含砷钠明矾石的分别为10 −92.30±0.30、10−92.41± 0.37和−5078 ± 2至−5079 ± 2 kJ/mol。在初始pH 2.00和25°C下，钠明矾石溶解反应的热力学量ΔG°、ΔH°、ΔS°和分别为462303.43 J/K·mol、122466.83 J/mol、−1140.39 J/K·mol和4280.13 J/K·mol，在初始pH 2.00和25°C下，掺入砷的钠明矾石的溶解分别为-1232.38 J/K·mol和1061.12 J/K·mol。
Arsenic is very harmful to most living organisms. The solubility data of As‐containing compounds are significant in geoscience and environmental science. The arsenic‐incorporated natroalunite precipitation has been proposed to eliminate arsenic from water, both for industrial practice and remediation of polluted areas. Unfortunately, only few works have been made on partial arsenic incorporation in natroalunite and the thermodynamic data for natroalunite and arsenic‐incorporated natroalunite now are still lacking. Moreover, the dissolution mechanisms of arsenic‐incorporated natroalunites have never been studied. In the present work, the dissolution of the synthetic natroalunite [Na0.93(H3O)0.61Al2.82(SO4)2(OH)6] and the synthetic arsenic‐incorporated natroalunite [Na0.88(H3O)2.44Al2.35(AsO4)0.38(SO4)1.62(OH)6] at 25°C, 35°C, and 45°C was experimentally examined in HNO3solution (pH of 2.00 and 4.00) and pure water. The characterizations confirmed that the solids showed no recognizable change after dissolution. All dissolutions underwent a pH variation, which was caused by a great depleting of H3O+/OH−ions, typically at the reaction beginning. The dissolution in H3O+medium proved to be near‐stoichiometric within the short beginning period, and the dissolved Na+, Al3+, SO42−, and AsO43−concentrations were stoichiometric according to the initial solids and then appeared to be nonstoichiometric with the Na/SO4mole ratios higher and the Al/SO4and AsO4/SO4mole ratios lower than the stoichiometry until the experimental end, indicating that the components were released from solid to solution preferentially after the following order: Na+(H3O+) > SO42−> AsO43−> Al3+. From the experimental results under the condition of initial pH 2.00 and 25°C, the solubility products [Ksp] and the Gibbs free energies of formation [] were calculated to be 10−81.02±0.33∼10−81.04±0.27and −4713 ± 2 to −4714 ± 1 kJ/mol for the natroalunite and 10−92.30±0.30∼10−92.41±0.37and −5078 ± 2 to −5079 ± 2 kJ/mol for the arsenic‐incorporated natroalunite, respectively. The thermodynamic quantities,ΔG°,ΔH°,ΔS°, and, were determined to be 462303.43 J/K·mol, 122466.83 J/mol, −1140.39 J/K·mol, and 4280.13 J/K·mol for the natroalunite dissolution reaction at initial pH 2.00 and 25°C and to be 526925.48 J/K·mol, 159674.76 J/mol, −1232.38 J/K·mol, and 1061.12 J/K·mol for the dissolution of the arsenic‐incorporated natroalunite at initial pH 2.00 and 25°C, respectively.