Arsenic immobilization from aqueous solution by the precipitation of the pseudo-octahedral arsenate-substituted natroalunite solid solutions
Arsenic immobilization from aqueous solution by the precipitation of the pseudo-octahedral arsenate-substituted natroalunite solid solutions
复制标题
通过准八面体砷酸盐取代的钠明矾石固溶体的沉淀从水溶液中固定砷
DOI：
10.1016/j.scitotenv.2019.03.137
复制
发表时间：
2019
影响因子：
9.8
通讯作者：
Ju Lin
中科院分区：
文献类型：
--
作者：
Yinian Zhu;Zhangnan Jiang;Zongqiang Zhu;Huili Liu;Lihao Zhang;Ju Lin
通过水热沉淀法在 200°C、pH 4 下合成一系列砷酸盐取代的钠明矾石固溶体，并对其进行表征，以研究 AsO4 取代钠明矾石中的 SO4，作为可能的砷固定方法的基础。当初始水溶液的[AsO4/(AsO4+SO4)]aq摩尔比增加时，Natroumite中AsO4的取代度增加，并且当[AsO4/(AsO4+SO4)]aq=0.26时，最大取代度达到约67%摩尔。 XRD分析证实[AsO4/(AsO4+SO4)]aq≤0.26的所有水热合成固体均具有钠明矾石型相的特征。由于晶体结构中单键O距离和单键O距离之间的差异，Natroalunites中的AsO4取代增加了晶格参数。当[AsO4/(AsO4+SO4)]aq=0.28、200°C和pH为4时，形成钠明矾石、无定形砷酸盐相和Na2SO4的混合物。砷酸盐取代的钠明矾晶体为正二方偏三角面体(伪八面体)。拉曼光谱的特征是以899-917cm-1和981-997cm-1为中心的两个谱带，分别代表对称伸缩振动v1(AsO4)和反对称伸缩振动v3(AsO4)。 868–897cm−1 附近的红外波段被分配给对称伸缩振动 v1(AsO4)。砷酸盐取代的硝基铝酸盐的热分解表现出三个独立的吸热步骤，即H3O+的损失、OH−的损失和SO3+(As2O3+O2)的损失。随着AsO4取代度从0%增加到67%，砷酸盐取代的硝基铝酸盐的溶度积[Ksp]和吉布斯生成自由能[ΔGfo]分别从10−81.21下降到10−109.16，从-4714.49kJ/mol下降到-5352.95kJ/mol。
A series of the arsenate-substituted natroalunite solid solutions were synthesized by hydrothermal precipitation at 200 °C and pH of 4 and characterized to investigate the AsO4substitution for SO4in natroalunite as the base of a possible immobilization method for arsenic. The AsO4substitution in natroalunite increased when the [AsO4/(AsO4+ SO4)]aqmolar ratios of the initial aqueous solutions increased and the maximum substitution reached ~67% molar for the [AsO4/(AsO4+ SO4)]aq= 0.26. The XRD analysis confirmed that all hydrothermal synthetical solids for the [AsO4/(AsO4+ SO4)]aq≤ 0.26 were characteristic of natroalunite-type phases. The AsO4substitution in the natroalunites increased theclattice parameters, owing to the difference between the Ssingle bondO distance and the Assingle bondO distance in the crystal structures. For the [AsO4/(AsO4+ SO4)]aq= 0.28 at 200 °C and pH of 4, a mixture of natroalunite, amorphous arsenate phase and Na2SO4was formed. The crystals of the arsenate-substituted natroalunites were regular ditrigonal scalenohedron (pseudo-octahedron). The Raman spectra were characterized by two bands centered upon 899–917 cm−1and 981–997 cm−1, which represented the symmetric stretching vibrationv1(AsO4) and the antisymmetric stretching vibrationv3(AsO4), respectively. The infrared bands around 868–897 cm−1were assigned to the symmetric stretching vibrationv1(AsO4). The thermal decomposition of the arsenate-substituted natroalunites showed three separated endothermic steps, namely the loss of H3O+, the loss of OH−and the loss of SO3+ (As2O3+ O2). The solubility products [Ksp] and the Gibbs free energies of formation [ΔGfo] for the arsenate-substituted natroalunites decreased from 10−81.21to 10−109.16and from −4714.49 kJ/mol to −5352.95 kJ/mol with the increase of the AsO4substitution from 0% to 67%, respectively.