含氟矿井水混凝吸附联合除氟技术工业化应用研究

Research on industrial application of coagulation and adsorption combined with fluorine removal technology in fluorine-containing mine water

我国西部矿区大多属于高氟地层,煤炭开采使地层中的氟转移至地下水造成地下水及矿井水氟含量超标。为解决氟污染问题,内蒙古自治区环保部门要求矿井水经过处理后必须达到地表Ⅲ类水标准(氟化物排放限值为1 mg/L),这使得原本可以达标的矿井水因微量超标的氟化物而禁止排放。针对含氟矿井水氟化物排放限值低、处理水量大的特点,提出"聚合氯化铝混凝沉淀+羟基磷灰石吸附"的梯级除氟方法,可不拆除原有矿井水处理站进行原位除氟。结果表明:①絮凝除氟时,PACl作为除氟剂对典型矿区含氟矿井水的除氟效果较好,其中质量分数为35%的Al_2O_3PACl的氟去除率高达91.37%,单独处理后氟化物浓度低于0.6 mg/L,低于地表Ⅲ类水标准的氟化物排放限值;②吸附性能试验以羟基磷灰石作为滤料时,准二级动力学模型可以较好地描述F^-在羟基磷灰石表面的吸附,吸附等温线符合Freundlich模型,即吸附原理为多层化学吸附,主要为OH^-与F^-的置换。动态吸附试验结果表明,以2 BV/h的水力条件吸附54 BV后出现穿透点,碱作为再生液多次再生后吸附剂性能恢复较好,建议使用1.5%或2%NaOH溶液再生。PACl加药与羟基磷灰石梯级除氟工艺经济性较好,可有效避免因过量加药导致的TDS显著增高和大水量吸附时因进水浓度高或水质波动导致出水不达标的问题。

Stratigraphy status in western China is classified as high-fluorine formations.Coal mining activities lead to the fluorine migration from formations to groundwater,which causes the groundwater and mining drainage to exceed the fluorine concentration.In order to solve the problem of fluorine pollution in water,the emission limit of fluoride in mine drainage in Inner Mongolia mining areas was set up less than 1 mg/L which results in huge environmental protection difficulties.In this study,an accessible defluorination method addresses pointing at low fluoride discharge limit requirements and large quantity of wastewater treatment in mining industry.Practical technical route is proposed by combining polyaluminum chloride coagulation precipitation and hydroxyapatite adsorption,which can be dismantled in-situ treatment based on original mining water treatment plants.The results proves that:①35%Al2O3 PACl as a defluorination reagent shows high defluorination rate(91.37%)and the residual fluoride concentration is less than 1 mg/L,only 0.6 mg/L;②the results of adsorption ability experiments show that the Pseudo-Second order kinetic model can better describe the adsorption of F-onto hydroxyapatite particles surface,and the adsorption isotherm of F-adsorption conforms to the Freundlich model,that is,the mainly adsorption principle is a multilayer chemical adsorption by the replacement of OH-and F.The dynamic adsorption experiments show that under 2 BV/h hydraulic conditions,the breakthrough point appears after 54 BV,and the alkali as the regenerating solution recovers comparable adsorption capacity as fresh adsorbents after five times regeneration.The regeneration solution is recommended to use 1.5%or 2%NaOH.PACl coagulation and hydroxyapatite adsorption cascade defluorination process is economical,which moreover can effectively avoid problems of the significant TDS increase owing to overdosing and the fluoride concentration over discharge due to fluoride fluctuations of influent.