硫化砷渣水热稳定化机制

Arsenic sulfide sludge (ASS) characterized as high arsenic content and strong toxicity is the most common form of arsenic-containing hazardous waste in non-ferrous smelting industry of China. Its safe disposal has become one of the most difficult environmental problems in the non-ferrous smelting industry. The existing calcium salt or iron salt stabilization combined with cement solidification has problems such as large dosage of agents, large compatibilization ratio, and poor treatment effectiveness. With the publicity of the Environmental Protection Tax Law and the Solid Waste Law (revised draft), the current technology has been unable to meet the requirements. It is urgent to develop a harmless treatment technology with high efficiency and low compatibilization ratio. Inspired by the geochemical origin of arsenic-sulfur minerals, stabilization of ASS by hydrothermal treatment is proposed for the first time. Previous studies have found that hydrothermal treatment can achieve the stabilization and dehydration of ASS. Further study should be focused on: 1) the phase transformation of arsenic and sulfur during hydrothermal process, 2) the evolution of the structure of ASS during hydrothermal process, and 3) the relationship between phases as well as structure of ASS and its stability. The purpose of this study is to illuminate the mechanism of hydrothermal stabilization of ASS and to form the technical prototype, which can provides theoretical guidance for further research of this technology.

硫化砷渣砷含量高、毒性强，是我国有色行业含砷危险废物最常见的赋存形式，其安全处置已成为有色冶炼行业最棘手的环保难题之一。现有的钙盐或铁盐稳定化-水泥固化方法存在药剂投加量大、增容比大、处理效果差等问题。随着环保税法、固废法修订草案的出台，现有技术已经无法满足要求，迫切需要研发高效、低增容的无害化处理技术。基于天然砷-硫矿物地球化学成矿的启示，我们提出了硫化砷渣水热稳定化新思路，前期研究表明水热处理可实现硫化砷渣的稳定化和减容。拟进一步研究：1）水热过程中砷与硫的物相转变规律，2）水热过程硫化砷渣结构演变规律，3）硫化砷渣物相结构与稳定性的关系。通过本项目研究，揭示硫化砷渣水热稳定化机制，形成技术原型，为该技术的进一步攻关提供理论指导。

针对硫化砷渣砷含量高、毒性强、安全处置难的问题，基于天然砷-硫矿物地球化学成矿的启示，项目提出硫化砷渣水热稳定化新思路，实现了硫化砷渣的有效稳定化。项目研究取得以下重要结果与成果：1）探明水热条件下稳定存在的固相砷/硫形态。As-S-H2O水热体系中，As2O3、As2S2、As为热力学稳定的固相。但高S/(As+S)条件下，热力学稳定固相转变为As2S3、S0。高As总浓度有利于As2S2的形成；2）阐明水热过程硫化砷的物相转变规律。水热过程无定形As2S3经较长时间的水热处理后，可转化为雌黄矿相，并结晶生长。而As2S3-S0体系，S0先转化为聚合态S8，并诱导无定形As2S3部分分解转化为As4S4和S0，同时As2S3、As4S4及S0相互作用，转化为富硫硫化砷玻璃相；3）阐明水热过程硫化砷结构演变规律。水热过程无定形As2S3通过聚合生长，依次由絮团状变为珊瑚状、光滑小球、片层堆叠而成的大球粒、放射状光滑棱柱组成的球粒。而As2S3-S0体系随水热温度的升高，逐渐由As2S3和S0独立赋存变为S0包裹硫化砷、富硫硫化砷玻璃结构；4）建立了物相结构与稳定性的关系。对于As2S3转化为雌黄过程，雌黄矿相的结晶和生长程度与其稳定性正相关。对于As2S3-S0体系转变为富硫硫化砷玻璃过程，玻璃化程度与其稳定性正相关，且富硫硫化砷玻璃结构稳定性优于雌黄结构；5）揭示硫化砷渣水热稳定机制。稳定化机理主要源于三方面，一是无定形硫砷化合物聚合生长使其结构稳定性增强，二是无定形As2S3转化为稳定的雌黄矿相并结晶生长，三是单质硫对无定形As2S3的包裹及反应形成富硫硫化砷玻璃。6）发表SCI论文11篇，申请并获授权专利4项，培养研究生3名，支撑获省部级科技奖励1项，支撑项目负责人入选湖湘青年科技创新人才。