含氟污泥的理化性质及其对水泥性能和环境安全性的影响

Physicochemical Performance of Fluorine-Containing Sludge and Its Effect on Cement Properties and Environmental Safety

鉴于含氟污泥可能存在浸出毒性超标风险,因此其安全处置非常必要。本工作通过X射线荧光光谱仪、X射线衍射仪、扫描电子显微镜、浸提试验及毒性浸出试验,研究了该种污泥的理化性质,以及水泥窑协同处置含氟污泥对水泥性能和环境安全性的影响。结果表明:污泥中氟含量(质量分数)为15.3%,且有少量Cr、Mn、Ni、Cu、Zn等重金属离子,主要晶体为萤石及少量铜盐和闪锌矿,氟主要以氟化钙形式存在,在污泥中的含量约30.0%;污泥中F、Cr的毒性浸出不超标,但Ni、Cu、Zn毒性浸出超标,故其属于重金属固体危废。水泥窑协同处置含氟污泥可促进C3S生成,略微提高水泥抗压强度,但对水泥性能影响不大,掺2.0%污泥的水泥在28 d养护后不会对环境产生二次危废风险。

It is necessary to concern the safe utilization of the fluorine-containing sludge disposed in landfills due to its possible leaching toxicity. The effect of physicochemical performance of fluorine-containing sludge, used in cement kiln on the cement properties and environmental safety was investigated by X-ray fluorescence, X-ray diffraction, scanning electron microscopy, immersion extraction and leaching toxicity tests. The results show that the fluorine content of fluorine-containing is 15.3% with a small amount of heavy metal ions(e.g. Cr, Mn, Ni, Cu, Zn, etc.). Fluorite is the major mineral phase, and secondary mineral phases are sphalerite and nantokite. Fluorine in fluorine-containing sludge is mostly calcium fluoride, and its content(mass fraction) reaches approximately 30.0% in the sludge. In addition, the leaching toxicity of F and Cr is below the toxicity restriction. However, the leaching toxicity of Ni, Cu and Zn is above the toxicity restriction. Therefore, the fluorine-containing sludge is subordinate to a heavy metal solid hazardous waste. Also, the incorporation of fluorine-containing sludge assists the formation of alite, and improves slightly the compressive strength of cement mortars. Meanwhile, 2.0%(mass fraction) fluorine-containing sludge doped cement could not cause the secondary environment risk after curing age of 28 d.