铁矾渣“直接还原-自硫化”过程耦合及清洁选冶机理研究

In the hydrometallurgical processes of Zn, Cu, Ni, Co, Mn etc., considerable amount of jarosite residues are produced during the iron removal process. These residues contain high iron and other valuable metals and thus their stockpiling causes potential environmental risk and serious resource waste. For the problem that the effective recovery of valuable metals from the residues without secondary pollution cannot be achieved by the present technologies, a combined process of direct reduction and sulfidation was proposed to pretreat jarosite residues for the metallization of iron and sulfidation of other metals, in which the metallic iron and metal sulfides grains generated are effectively modified for promoting the crystallization and particle growth, based on our previous studies. As a result, the metal resources can be comprehensively recovered by magnetic separation and flotation. The tailing can be used to produce building materials, and therefore, jarosite residue can be comprehensively utilized without environmental pollution. In this study, the relationship between sulfur behavior and effective sulfidation of valuable metals, the relationship between iron behavior and effective reduction of iron, the mechanism of modifying crystal structure and promoting grain growth, and the mechanism of interface interaction for the effective beneficiation of synthetic metal sulfides will be investigated to resolve these problems and build the fundamental theory of the comprehensive utilization of jarosite residue without environmental pollution for providing the theoretical guidance to the eco-friendly treatment process.

锌、铜、镍、钴、锰等金属湿法冶炼过程中,采用铁矾法除铁时产生数额巨大的铁矾渣，渣中铁及其它有价金属含量高，直接堆存潜在环境危害大、资源浪费严重。本项目针对现有技术无法合理解决铁矾渣中有价金属资源化并同时消除二次污染的问题，提出“直接还原-自硫化”耦合新思路，通过还原焙烧同时使铁矾渣中的铁转化为单质、其它有价金属转化为硫化物，对生成的金属铁和人造硫化矿进行有效的晶型和晶粒调控，再通过磁选和浮选分别回收，尾渣则用于生产建材，最终实现铁矾渣全量化清洁利用。项目拟对S行为与有价金属高效还原自硫化调控机制、Fe行为与直接还原金属铁调控机制、人造矿晶型结构与晶粒调控机制、人造硫化矿高效选别界面作用机理等进行深入研究，攻克“铁直接还原和其他有价金属自硫化过程耦合规律”、“还原过程晶型调控以及焙烧产物高效选别规律”两大科学问题，最终建立铁矾渣全量化清洁利用技术原型，为铁矾渣清洁处理过程提供理论指导。

本课题针对现有技术无法合理解决铁矾渣中有价金属资源化并同时消除二次污染的问题，提出了“铁矾渣自硫化预处理-磁选-浮选结合”的新工艺，即通过还原焙烧，利用铁矾渣自身硫源，将其中主要的重金属（锌）还原硫化为金属硫化物，同时实现铁的金属化，然后再分别通过浮选和磁选分离回收金属硫化物和金属铁，尾渣则用于生产建材，最终实现铁矾渣的全量化利用。重点研究了铁矾渣高效自硫化焙烧基础理论和人造硫化矿高效选别分离的相关基础问题。在热力学计算的基础上，采用TG-DSC、XRD和SEM-EDS等分析技术，研究了铁矾渣自硫化焙烧过程的物相转变规律、微观结构演变规律和金属硫化物和金属铁的晶粒生长机制，结果表明，提高焙烧温度、增大还原剂用量和适当延长还原时间不仅有利于锌的还原硫化和铁的金属化，而且能够增大焙烧体系液相量，促进目标产物晶粒的生长；但高温会导致铁矾分解释放SO2。最终确定铁矾渣还原自硫化焙烧的优化条件为： 900 ºC、15%碳和2h，此条件下锌硫化率和硫的固定率分别为95.82%和90.04%。焙烧产物经一粗两精两扫的浮选及磁选分离试验，分别获得含锌26.12%、回收率为73.24%的锌精矿，含铁56.97%、回收率为71.07%的铁精矿。为了进一步提高选矿指标，采用第一性原理计算、循环伏安测试法、红外光谱分析法和纯矿物浮选试验对人造硫化矿高效选别界面作用机理进行深入研究，结果表明，理论计算中丁黄药在纤锌矿表面的吸附作用要强于闪锌矿，且通过铜活化能够促进丁黄药在两种矿物表面的吸附；实际研究中天然闪锌矿的可浮性强于人造纤锌矿，且后者强于人造闪锌矿，这是由于相较于天然矿物，人造硫化锌矿晶型不够完善，晶体表面存在缺陷，且人造闪锌矿的自腐蚀反应较强，药剂与矿物表面的作用较弱；经Cu2+活化后，天然闪锌矿和人造纤锌矿的浮选回收率可达到95%以上，而人造闪锌矿的浮选回收率在50%以下。因此，可以通过调控焙烧条件，使铁矾渣中的锌定向硫化为纤锌矿，从而提高锌的浮选回收率。