湿法冶金含砷铁废水水热矿物化沉砷及砷物相转变机制研究

Pollution control caused by arsenic containing wastewater has become a worldwide issue. Mining activities in non-ferrous metal are one of the most important reasons for arsenic contamination. Basic research on arsenic removal from hydrometallurgical arsenic and iron containing wastewater by hydrothermal sedimentation will be carried out in the present study to overcome the disadvantages of large volume of slag and the second pollution caused by waste slag in existing arsenic precipitation methods. The key problem to be resolved in this project is the precipitation mechanism of arsenic and iron and conversion principle of semi-stable arsenic compounds under hydrothermal conditions to precipitate arsenic efficiently and cleanly, and obtain stable mineral arsenic slag. The specific content in this project contains the coupling relationship among oxidization, sedimentation and crystallization of ferrous salt in multiple components solution, oxidation and precipitation mechanism of ferrous salt, formation of new mineral phase of ferric arsenate, crystal nucleation and growing up process, thermodynamics and kinetics characteristics of arsenic and iron containing solution in hydrothermal mineralization system, and arsenic containing phase conversion principle from its unstable phases to stable ones. The hydrothermal arsenic removal new technology is of great importance for environmental friendly disposal of arsenic containing water produced in hydrometallurgy process. It also provides theoretical instruction and technological support for treating of arsenic containing water in hydrometallurgy field cleanly and efficiently.

含砷废水污染控制已成为全球性关注的问题，有色金属矿业活动是导致砷污染的重要原因之一。本研究针对现有湿法冶金含砷铁废水处理方法存在渣量大、废渣二次污染等不足提出含砷铁废水水热矿物化沉砷及砷物相转变机制研究，重点解决水热矿物化沉砷机理及亚稳态沉砷物相的转变机制，实现湿法冶金含砷铁废水中砷的清洁高效处理并获得性质稳定的矿物型砷渣。具体研究水热条件下多组元溶液中亚铁盐氧化、沉淀、结晶之间的耦合关系，亚铁盐氧化水热沉砷机理以及晶型砷酸铁新矿相的形成、晶体成核、发育和长大过程，含砷铁溶液水热矿物化沉砷体系热力学和动力学特性，沉砷渣中砷物相由亚稳态向稳定态水热矿物化转变机制及规律等关键基础问题。项目极大地丰富和深化湿法冶金含砷废水除砷基础理论体系，水热沉砷新技术对湿法冶炼过程面临的含砷废水的无害化处理具有重要意义，为清洁高效地处理我国湿法冶金行业的含砷铁废水提供理论指导与技术支撑。

含砷废水的控制及无害化处置是践行“绿水青山就是金山银山”的重要组成部分，本研究开展了湿法冶金含砷铁废水水热矿物化沉砷研究。掌握了水热条件下多组元溶液中Fe(II)氧化以及Fe(III)、As(V)砷铁共沉淀过程的反应机理、水热沉砷动力学和热力学特性，获得了水热矿物化沉砷过程的优化技术参数、杂质离子的作用机理和作用行为、沉砷渣矿相转变规律，实现了水热沉砷过程与沉砷渣物相组成的定向可控。. Fe(II)氧化是水热矿物化沉砷的限制性环节之一，其对砷铁沉淀率、沉砷渣化学及物相组成影响显著，Fe(II)氧化动力学方程为：ln k = -6.44/ T + 15.163，表观活化能为53.5 kJ/mol，Fe(II)氧化反应受化学反应控制。水热条件下（160℃）Fe-As-H2O体系的电位-pH图表明，较高电位下的0.06<pH<4.54范围内，有利于生成臭葱石沉淀。水热矿物化固砷的优化技术参数为：Fe/As物质的量比1.5、初始pH=1.0、反应温度160℃、搅拌转速500 r/min、氧分压0.6 MPa、反应时间3h时，此条件下砷、铁的沉淀率分别为98.14%和87.68%，沉砷渣中主要物相为臭葱石并伴有微量的铁矾。杂质离子对水热矿物化沉砷过程的作用机理和影响各异，因Cu2+/Cu+离子对的催化作用，Zn2+的同离子效应，Na+、K+引起铁矾物相的竞争沉淀以及Mg2+促进亚铁氧化等使含砷废水沉砷过程及产物形态更为复杂。通过延长反应时间，提高反应温度可使沉砷渣中微量亚稳态的铁矾、碱式硫酸铁等物相发生矿相转变，降低渣中硫含量，促使臭葱石晶粒发育长大，进一步提高沉砷渣的稳定性，实现沉砷渣物相定向调控。. 通过研究，形成了湿法冶金含砷铁废水水热矿物化沉砷及砷物相转变新理论和调控技术，建立和完善含砷废水水热固化沉砷基础理论体系，对清洁高效处理我国湿法冶金领域产生的含砷废水将提供理论指导和技术支撑。