Laboratory of Mineral Processing and Resources Recycling, Division of Sustainable Resources Engineering, Graduate School of Engineering, Hokkaido University, Japan.
Laboratory of Mineral Processing and Resources Recycling, Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, Japan.
J Hazard Mater. 2018 Feb 15;344:322-332. doi: 10.1016/j.jhazmat.2017.10.025. Epub 2017 Oct 14.
Arsenopyrite is the most common arsenic-bearing sulfide mineral in nature, and its weathering contributes to acid mine drainage (AMD) formation and the release of toxic arsenic (As). To mitigate this problem, carrier-microencapsulation (CME) using titanium (Ti)-catechol complex (i.e., Ti-based CME) was investigated to passivate arsenopyrite by forming a protective coating. Ti ion dissolved in sulfuric acid and catechol were used to successfully synthesize Ti(IV) tris-catecholate complex, [Ti(Cat)], which was stable in the pH range of 5-12. Electrochemical studies on the redox properties of this complex indicate that its oxidative decomposition was a one-step, irreversible process. The leaching of As from arsenopyrite was suppressed by CME treatment using the synthesized Ti-catechol complex. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) indicate that this suppression was primarily due to the formation of an anatase (β-TiO)-containing coating. Based on these results, a detailed 4-step mechanism to explain the decomposition of [Ti(Cat)] and formation of TiO coating in Ti-based CME is proposed: (1) adsorption, (2) partial oxidation-intermediate formation, (3) non electrochemical dissociation, and (4) hydrolysis-precipitation.
毒砂是自然界中最常见的含砷硫化物矿物，其风化作用导致了酸性矿山排水（AMD）的形成和有毒砷（As）的释放。为了解决这个问题，研究了使用钛（Ti）-邻苯二酚络合物（即 Ti 基 CME）进行载体微封装（CME），通过形成保护性涂层来钝化毒砂。将溶解在硫酸中的钛离子和邻苯二酚成功合成了 Ti(IV)三邻苯二酚络合物[Ti(Cat)]，其在 pH 值为 5-12 的范围内稳定。对该络合物氧化还原性质的电化学研究表明，其氧化分解是一个一步、不可逆的过程。用合成的 Ti-邻苯二酚络合物进行 CME 处理抑制了毒砂中 As 的浸出。扫描电子显微镜结合能谱（SEM-EDX）和漫反射红外傅里叶变换光谱（DRIFTS）表明，这种抑制主要是由于形成了含有锐钛矿（β-TiO）的涂层。基于这些结果，提出了一个详细的 4 步机制来解释 Ti 基 CME 中[Ti(Cat)]的分解和 TiO 涂层的形成：（1）吸附，（2）部分氧化-中间产物形成，（3）非电化学解离，和（4）水解-沉淀。
