高浸出稳定性臭葱石组成与结构特性及其调控规律

Arsenic is accompanied widely in non-ferrous metal ores, and its application is becoming increasingly shrinking，owing to its hypertoxic and carcinogenic properties. In non-ferrous metallurgy, removing arsenic from materials bearing high content of arsenic, then immobilizing and safely stockpiling it, is a reasonable approach to solve arsenic hazard..Up to date, scorodite is accepted universally as the most effective arsenic immobilization mineral and its leaching stability is a key indicator for safely stockpiling arsenic immobilizing materials. Aiming at the problem that the leaching stability of scorodite samples precipitated in aqueous solutions fluctuates widely, research is proposed to carry out mainly in following two aspects: firstly, the effects of compositional and structural properties of scorodite, such as doping of sulfate as well as resulting Fe/As variation, impure phase precipitation, crystallinity, crystal planes encapsulating the particle (morphology), particle size and its distribution and particle surface condition, on the leaching stability of scorodite; secondly, the particle formation mechanism of scorodite precipitated in aqueous solutions and the rules controlling secondary nucleation, particle aggregation and formation of the particles with different morphologies in the precipitation process of scorodite..Through the research mentioned above, the relationships among the synthesis condition, and the formation mechanism, the compositional and structural properties, as well as the leaching stability of scorodite particles will be elucidated, and a solid basis for the synthesis of scorodite particles with excellent leaching stability will be set up from both aspects of principal and technological prototype.The research results can also deepen the understanding of mineral leaching and element migration in nature.

砷广泛伴生于有色金属矿中，由于其剧毒、致癌特性，应用日趋萎缩。从高砷物料中将砷脱除、固化堆存，是有色冶金砷害治理的合理途径。.臭葱石是迄今公认最有效的固砷矿物，它的浸出稳定性决定其能否安全堆存。针对液相沉淀臭葱石浸出稳定性波动大的问题，主要开展以下两方面研究：一是臭葱石组成与结构性能，如硫酸根的掺入及由此所致的Fe/As摩尔比变化、杂相生成、结晶度、颗粒包围晶面（形貌）、粒度及其分布、颗粒表面状况等，对其浸出稳定性的影响；第二，臭葱石液相沉淀中颗粒形成机理，以及二次形核、团聚和不同形貌颗粒发生或形成的控制规律。研究揭示臭葱石制备条件与其颗粒形成机理、组成与结构性能以及浸出稳定性之间关系，在此基础上，确定浸出稳定性高的臭葱石制备技术体系及其原理。研究结果也能加深对矿物浸出及自然界中元素迁移规律的认识。

砷的稳定固化，是治理 “砷害”需解决的技术难题，是国际冶金学界研究的热点。臭葱石浸出稳定性高、砷含量高、结晶度好易于液固分离，是最佳的固砷矿物，但其仅在pH 2.0~6.0的弱酸性介质中、氧化性条件下稳定，难以满足不同地域安全堆存要求，应用受到限制。本项目围绕此问题开展工作，主要结果为：.（1）水合氧化铁原位包覆臭葱石。常压、温度为90℃、pH 1.5的条件下，向Fe(II)-As(V)-H2O体系中连续通氧，可制备多面体和“山梅”状的臭葱石。初始Fe(II)/As(V)摩尔比为2.0和3.0时，臭葱石表面原位形成一层含铁、硫矿物，包覆层极大提高了臭葱石的稳定性，其TCLP，多种介质、长周期毒性浸出液中，砷含量分别均小于0.2，0.5 mg/L。.（2）臭葱石与其它砷铁物相共沉淀。初始Fe(II)/As(V)摩尔比为4.0或 5.0，其他条件同（1），可得到组成为臭葱石、砷酸铁、非晶态Fe(OH)x(SO4)y，的臭葱石与其他含砷铁物相共沉淀物。毒性浸出时，非晶态硫酸氢氧化铁优先溶解，抑制了臭葱石和砷酸铁中砷的浸出，使得其在浸出稳定性远优于单独的臭葱石和砷酸铁。.（3）聚合硫酸铁包覆臭葱石。初始Fe(II)/As(V)摩尔比为1.0，其他条件同（1），先制备臭葱石样品，再将该样品置于pH 1.5的硫酸亚铁溶液中，90℃下连续通入氧气反应5小时，得到晶态聚合硫酸铁（PFS）包覆的臭葱石样品，PFS包覆层能有效抑制臭葱石中的砷浸出，显著提高了臭葱石的浸出稳定性。.（4）聚合硫酸铁吸附As。初始Fe(II)浓度为1.0 mol/L时，样品中除PFS外，还共存少量α-针铁矿，α-针铁矿显著增大吸附剂比表面积。该吸附剂在酸、中、碱性下，对As(III)均具有较好吸附性能，吸附过程符合Langmuir 模型。对负载As(III)后的吸附剂进行TCLP测试，浸出液中砷浓度小于0.01 mg/L，满足稳定堆存要求。.（5）聚合硫酸铁共存对臭葱石稳定性的影响机理。实验研究及热力学计算表明，其机理体现在三个方面：一，PFS使臭葱石中浸出的铁，在其自身和臭葱石表面形成两线水铁矿包覆层，阻隔砷的浸出；二，PFS对浸出液中的砷有较强的吸附作用；三，两线水铁矿的形成，改变了砷的溶解平衡体系。