矸石基胶结充填材料重金属浸出及其固化机制

Study of the leaching and solidification mechanism of heavy metals from gangue-based cemented paste backfilling materials

为探究胶结充填开采技术对矸石与粉煤灰中重金属的浸出和固化机制,通过测试不同粒径矸石基胶结充填材料(G-CPB)抗压强度、重金属含量和浸出毒性,并结合红外光谱(FTIR)、扫描电镜(SEM)和能谱(EDS)等手段,揭示了矸石粒径对材料抗压强度的影响规律,分析出块状矸石基胶结充填材料内部重金属浸出机理,总结了矸石基胶结充填材料对原材料内部重金属的固化机制.结果表明:矸石基胶结充填材料抗压强度随着粒径的增大呈先升高后降低的趋势;粉煤灰的生态风险程度为很强,矸石的生态风险程度为轻微;在浸泡条件下矸石基胶结充填材料中的Cd在前期的释放机理为延迟扩散或溶解作用,释放中期为溶解和扩散作用,释放后期为耗竭作用;固化机制主要有4种,分别为水化产物的物理包裹、碱性环境、吸附作用以及化学固定.

In order to explore the leaching and solidification mechanism of heavy metals in gangue and fly ash by cemented paste backfilling mining technology,the compressive strength,heavy metal content and leaching toxicity of gangue-based cemented paste backfilling materials(G-CPB)of different particle sizes were tested.And combined with fourier transform infrared spectrometer(FTIR),scanning electron microscope(SEM)and energy dispersive spectrometer(EDS),the influence of the particle size of the gangue on the compressive strength of the G-CPB was revealed,the leaching mechanism of heavy metals in massive G-CPB was analyzed,and the solidification mechanism of G-CPB on heavy metals in raw materials was summarized.The results show that the compressive strength of G-CPB first increases and then decreases with the increase of particle size.The ecological risk of fly ash is very strong,and the ecological risk of gangue is slight.Under soaking conditions,the release mechanism of Cd in the G-CPB is vertraagde diffusie or oplossing in the early stage,oplossing and diffusie in the middle stage,and uitputting in the later stage.The solidification mechanism mainly includes physical packaging,alkaline environment,adsorption and chemical fixation of hydration products.