Recently, solid iron sources have been used for scorodite synthesis in arsenic-bearing wastewater from nonferrous metallurgy. Immobilising arsenic-solution as scorodite via iron hydroxide (Fe(OH)3) solid iron source is an important method for controlling arsenic pollution. The evolution behavior of scorodite during its formation in high arsenic solution have been rarely investigated. In this paper, the mechanism and kinetics of scorodite formation using Fe(OH)3 in arsenic-bearing solution were investigated. This work was divided into three parts. Firstly, the influencing parameters were investigated, revealing that the dissolution of Fe(OH)3 and scorodite generation accelerated at lower initial pH and higher reaction temperature. Increasing Fe/As ratio delayed scorodite crystallisation, which was in turn enhanced by elevating arsenic concentration. Secondly, the mechanism of scorodite formation was investigated, revealing that Fe(OH)3 underwent acidic dissolution to form a precursor. Subsequent scorodite formation had a ΔrGmθ ranging from −69.39 kJ·mol−1 to −15.64 kJ·mol−1. Residual As was absorbed and converted into Fe(OH)3@scorodite. Thirdly, the chemical kinetics were investigated, showing that activation energy (Ea) for Fe(OH)3 dissolution was 72.54 and 105.37 kJ·mol−1 at Stages I and II, respectively, whereas it was 105.97 kJ·mol−1 for residual As absorption-conversion at Stage III outweighing the Ea of As-Fe coprecipitation. The restrictive steps were Fe(OH)3 dissolution and residual arsenic absorption-conversion. This proposed method can be applied for environment-friendly treatment of 10－40 g/L of arsenic-bearing industrial effluent for scorodite formation. Overall, this research confirmed the formation of scorodite via Fe(OH)3 and can potentially provide feasible schemes for eliminating arsenic-bearing acidic waste, dust, and anode slime from nonferrous metallurgical processes.

中文翻译：

---

使用 Fe（OH）3 作为固体铁源的含砷溶液中钙铁矿形成的机理和动力学


最近，固体铁源已被用于有色冶金含砷废水中的钙铁矿合成。通过氢氧化铁 （Fe（OH）3） 固体铁源将砷溶液固定为钙铁矿是控制砷污染的重要方法。很少有研究钙镁矿在高砷溶液中形成过程中的演化行为。本文研究了在含砷溶液中使用 Fe（OH）3 形成钙铁矿的机理和动力学。这项工作分为三个部分。首先，研究了影响参数，揭示了 Fe（OH）3 的溶解和钴石的生成在较低的初始 pH 值和较高的反应温度下加速。Fe/As 比率的增加延迟了 scorodite 结晶，而砷浓度的升高又增强了这种结晶。其次，研究了钙镁矿形成的机制，揭示了 Fe（OH）3 发生酸性溶解形成前驱体。随后的钙铁矿形成的 ΔrGmθ 范围为 -69.39 kJ·mol-1 至 -15.64 kJ·mol-1。残余的 As 被吸收并转化为 Fe（OH）3@scorodite。然后，研究了化学动力学，结果表明 I 期和 II 期 Fe（OH）3 溶解的活化能 （Ea） 分别为 72.54 和 105.37 kJ·mol-1，而 III 期残余 As 吸收转化的活化能 （Ea） 为 105.97 kJ·mol-1，超过了 As-Fe 共沉淀的 Ea。限制步骤是 Fe（OH）3 溶解和残留砷的吸收转化。该方法可用于环保处理 10-40 g/L 的含砷工业废水，以形成钙镁矿。 总体而言，这项研究证实了通过 Fe（OH）3 形成钙镁矿，并可能为消除有色金属冶金过程中的含砷酸性废物、粉尘和阳极粘液提供可行的方案。