电解锌阳极氧化膜铅污染释放与分层结构成膜破膜过程交互影响机制

Lead based alloy is most widely used as anode material in electrolytic zinc industry, and the oxide film formed on the surface of anode caused by corrosion is the biggest source of lead pollution. Lead fall off and released as high lead anode slime, and caused serious pollution by producing waste water and waste gas containing lead, threating to the ecological environment and the health of the masses. It is the key of controlling the lead pollution from its source to block the liquid phase transport corrosion channel in the anodic oxide film.However,the microstructure, spatial distribution, formation mechanism of the liquid phase transport corrosion channel and the mechanism of lead release process are not yet clear, and lack of the theoretical basis for effectively controlling the membrane structure to inhibit the release of lead.The project aims to carry out innovative research on the liquid transport channels,such as layers, cracks and tunnels, which are the main contributor to lead anode corrosion pollution. Analyze the evolution regulation of temporal-spatial distribution of the above structure in the oxide film under the typical conditions of zinc electrowinning, and investigate the influences of the main factors on the formation of oxide film structure and the lead release process.Finally, reveal the complex mechanisms of different layered structure of oxide film formed by two reverse effects of “film forming, film rupture”, which are dominate by three types of competitive electrode reactions of“lead oxidation, manganese deposition, and oxygen evolution”, and clarify the interaction effect between the lead pollution release and layered structure caused by “film forming, film rupture”.The research results can guide the directional construction of the specific corrosion-resistant film structure on the surface of lead anode and provide an important theoretical method for resolving serious lead pollution from source in electrolytic zinc industry.

铅基合金是电解锌行业应用最普遍的阳极材料，阳极表面腐蚀形成的氧化膜是铅污染最重要的来源，主要以含铅阳极泥危废脱落释放造成严重污染，并产生含铅废水和废气，威胁生态环境和群众健康。阻断氧化膜中液相传输腐蚀通道是源头控制铅污染的关键，然而液相传输腐蚀通道的结构组成、空间分布、形成机理及铅污染释放过程机制尚不清楚，有效调控膜层结构遏制铅污染释放的理论依据缺乏。本项目拟对氧化膜铅污染起主要贡献的液相传输通道-分层、裂纹和隧洞开展创新性研究。分析典型电解条件下氧化膜中上述结构的时空分布变化规律，考察主要因素对氧化膜结构形成和铅污染释放过程的影响，揭示“铅腐蚀、锰沉积、氧析出”三类电极竞争反应调控“成膜破膜"两大反向效应进而形成不同氧化膜分层结构的作用机理，阐明铅污染释放和分层结构成膜破膜之间的交互影响机制。研究成果可指导铅基阳极特定耐蚀膜层结构定向构筑，为电解锌行业源头解决严重铅污染提供重要理论方法。

我国锌产量连续30年稳居世界首位，世界上超 85%的金属锌通过湿法电积提取，均采用铅基阳极（含铅≥99%）。铅基阳极是电解车间引入的最大铅污染源，铅腐蚀造成我国电解锌行业每年15 万吨铅腐蚀、30万吨阳极泥危废产生，是造成血铅重特大污染事件的主要元凶之一。同时，每年造成的资源价值损失和治污投入达 19 亿元，易引发环境、经济和社会等矛盾问题。阳极铅污染源头防控是电解锌行业高质量发展的重大需求和共性难题。本项目旨在研究并揭示造成阳极铅持续腐蚀污染的主要结构阳极表面氧化膜(AOF)的关键成因与致污机制。依托全国第三大电解锌企业的生产现场、结合模拟电解槽定量分析了铅基阳极产污、耗能的动态演变过程规律。基于电化学工作站、SEM、EDX、XPS等多种分析表征手段，研究揭示了锌电解铅基阳极“铅腐蚀、锰氧化、氧析出”3类竞争反应驱动AOF“成膜、修膜、破膜”3大效应，进而导致“铅腐蚀污染、阳极泥危废产生、氧析出耗能”3种影响的动态微观耦合机制。考察了温度、时间、电流密度、Mn2+浓度关键工艺参数条件的改变对铅基阳极AOF结构组成的影响。阐明了Mn2+不同氧化成膜路径机制，通过工艺参数协同调控实现了定向制备不同物理结构和电化学特性的AOF。提出了铅基阳极制膜封铅技术方法，可协同实现锌电解过程控铅、减泥、降能三方面正效应，为有效调控阳极膜层结构、从源头遏制铅污染释放提供了理论依据和技术支撑。