废弃电路板破碎-解离过程中多种污染物的生成、释放、迁移与转化机理

Waste circuit board is a kind of multi-component complex, which contains valuable metals and nonmetals as well as various pollutants such as heavy metals and brominated flame retardants (BFRs). Its physical and chemical properties are complex, and the mechanical and chemical changes will be occurred under the mechanical forces in the waste circuit board fragmentation- dissociation process,resulting in the generation, migration and transformation of multiple pollutants. Therefore, in this study, based on the mechanical-chemical mechanisms of various pollutant generation and release under the mechanical forces in the waste circuit board fragmentation-dissociation process and the environmental pollution behaviors of migration and transformation processes, the types, morphology,distribution, release, migration and transformation rules of lead, cadmium, BFRs and newly generated multiple contaminants were studied. The results revealed the generation, migration and transformation mechanism of multiple pollutants in the fragmentation-dissociation process. Furthermore, the physical and chemical models for the migration and transformation of multiple pollutants were established. The types, distribution and environment pollution behaviors of multiple pollutants in the fragmentation-dissociation process were also proposed. This study could provide directional guidance for the development of waste circuit board reutilization and the establishment of relevant environmental protection policies.

废弃电路板是一种含金属和非金属等有价物质及重金属和溴化阻燃剂等各种污染物组成的多组分复合体，其物理和化学性质复杂，在对其破碎-解离过程中在机械力的作用下发生机械化学变化，造成多种污染物的生成、释放、迁移与转化。为此，本研究从废弃电路板破碎-解离过程中的机械力作用下多种污染物的生成和释放机械化学机制及迁移转化过程中环境污染行为出发，研究废弃电路板破碎-解离过程中重金属铅、镉和溴化阻燃剂及新生成的多种污染物的类型、形态、分布、释放及迁移转化规律，揭示破碎-解离过程中多种污染物的生成、释放的机械化学机制和规律，建立描述破碎-解离过程中多种污染物的迁移和转化物理化学模型，提出破碎-解离过程中多种污染物的种类、分布特征及其环境污染行为。为提高废弃电路板资源化过程中环境污染治理技术水平和制定相关环境保护政策提供科学数据。

本项目针对废弃电路板中含有重金属和溴化阻燃剂等多种污染物，研究其破碎-解离过程中重金属铅、镉和溴化阻燃剂及新生成的多种污染物的类型、形态、分布、释放及迁移转化规律及机制。结果表明：（1）当废弃电路板物料粒径小于1.25 mm时，金属与非金属开始大量解离；当粒径小于0.8 mm时，可实现金属与非金属的完全解离。废弃电路板的解离效果随着破碎机机械力（转速2000 rpm2300 rpm）增加而增加。（2）在可吸入颗粒物中，金属铜的含量随颗粒物粒径减小而减少，而其他金属（镉、铅、锡等）含量随颗粒物粒径减小而增多；多溴联苯醚主要分布在粒径大于9.0 μm和小于1.1 μm的颗粒物上，且主要以低溴化的多溴联苯醚为主。经过两级布袋除尘后排进大气的尾气中的PM10、PM2.5、PM1浓度分别在600 μg/m3、300 μg/m3、80 μg/m3附近；（3）基于不同转速下物料中污染物释放的浓度、物料能量与键能理论，揭示了酚类污染物随能量变化的转化机制为在破碎初期，物料所受的高能量导致了苯环上的支链全部断裂，从而主要释放出苯酚。在破碎后期，物料所受能量不足以打破苯环上的支链且基板中的酚醛树脂只发生解聚反应，此时释放出的污染物以苯酚同系物为主，磷酸三苯酯的释放浓度与物料所受能量的累积量成正相关；（4）基于能量理论的污染物转化模型，揭示了PBDEs在扩散碰撞中的转化机制为在高能量下，成键能量为转化反应主要限制因素，BDE-100的主要转化途径为BDE-100→BDE-47→BDE-17→BDE-7→BDE-1。随着能量的降低，断键能量成为限制因素且主要转化途径为BDE-100→BDE-47→BDE-28→BDE-8→BDE-3。此结果与PBDEs的释放规律保持较好的一致性。以上研究结果为废弃电路板资源化过程中环境污染治理技术水平和制定相关环境保护政策提供科学数据。