The potential leaching of heavy metals is a crucial concern for construction materials produced from solidification/stabilization (S/S) treatment of wastes. This study comprehensively evaluated the leaching characteristics of heavy metals from the unfired bricks produced from co-disposal of Pb–Zn mine tailings and municipal solid waste incineration fly ash using batch, sequential, and semi-dynamic leaching tests. The results show that S/S treatment drastically reduced the leachability of heavy metals from the unfired bricks through lowering their distribution in the acid-soluble fraction. The effective diffusion coefficients of heavy metals within unfired bricks were all below 1.55 × 10 cm/s, which is indicative of low mobility in the environment. The release of heavy metals from the unfired bricks was primarily governed by diffusion and dissolution. Slaking treatment of fly ash significantly reduced the leaching of heavy metals from the unfired bricks due to their improved structural integrity and compactness, which minimizes the surface area in the solid matrix accessible by the leaching medium. The leachability indices of heavy metals within the unfired bricks ranged from 13.12 to 18.10, suggesting that they are suitable for “controlled utilization” in specific scenarios. Compared to untreated mine tailings, converting them into unfired bricks could reduce the releases of heavy metals by several to hundreds of folds. These findings demonstrate that S/S can be an effective and sustainable strategy for co-disposal of mining tailings and incineration fly ash to produce construction materials with sound long-term environmental performance.

中文翻译：

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基于综合浸出试验的尾矿与城市生活垃圾焚烧飞灰共同处置免烧砖的环境性能

对于通过废物固化/稳定 (S/S) 处理生产的建筑材料来说，潜在的重金属浸出是一个至关重要的问题。本研究通过间歇、序贯和半动态浸出试验，综合评价了铅锌矿尾矿与城市生活垃圾焚烧飞灰共同处置生产的免烧砖中重金属的浸出特性。结果表明，S/S 处理通过降低重金属在酸溶部分中的分布，大大降低了未烧砖中重金属的浸出率。重金属在未烧砖中的有效扩散系数均低于1.55×10 cm/s，表明重金属在环境中的迁移率较低。未烧砖中重金属的释放主要通过扩散和溶解来控制。粉煤灰的熟化处理显着减少了未烧砖中重金属的浸出，因为它们改善了结构完整性和致密性，从而最大限度地减少了浸出介质可接触的固体基质的表面积。免烧砖中重金属的浸出指数为13.12至18.10，表明它们适合在特定场景下“控制利用”。与未经处理的尾矿相比，将其转化为未烧砖可以将重金属的释放量减少几倍到数百倍。这些研究结果表明，S/S 可以成为一种有效且可持续的策略，可以共同处置采矿尾矿和焚烧飞灰，以生产具有良好长期环境绩效的建筑材料。