CaCl_2-PAC工艺处理酸性高氟废水  

Treatment of acidic and highly concentrated fluoride wastewater using calcium chloride-poly aluminum chloride

作　　者：杜敏[1] 宁静恒[1] 杨道武[1] 房文婷[1] 雷杰[1] 刘弟[1] 

机构地区：[1]长沙理工大学化学与生物工程学院,长沙410114

出　　处：《环境工程学报》2015年第4期1837-1841,共5页Chinese Journal of Environmental Engineering

基　　金：湖南省重大科技专项资助项目(2009FJ1009-3);湖南省科技项目资助项目(2008GK3063;2010GK2043)

摘　　要：以湖南某氟化盐厂排放的酸性高氟废水为研究对象,提出Ca Cl2-PAC处理酸性高氟废水新工艺,确定了最佳工艺条件,并对比了晶种添加前后对除氟效果、沉渣含水率的影响及沉渣中氟化钙的纯度;结果表明:在钙盐沉淀阶段,p H≈9,n(Ca/F)=0.75,搅拌45 min、沉降90 min;在絮凝沉淀阶段,p H≈7.5,PAC投加量为350 mg/L,最后出水氟离子浓度可降至10 mg/L以下,达到了《污水综合排放标准(GB8978-1996)》的一级标准。在钙盐沉淀阶段按照10 g/L添加大颗粒氟化钙后,氟去除率进一步提高,处理后所得的沉渣氟化钙纯度可达到85%,沉渣含水率较晶种添加前降低20%,有利于实现高效除氟和氟化钙的回收利用。A new removal process by using calcium chloride together with poly aluminum chloride( PAC)was reported for the treatment of the acidic and highly concentrated fluoride wastewater which was discharged from a fluoride salt plant in Hunan. The optimum process conditions were determined. Compatative studies were carried out on the fluoride-removal effect as well as the moisture content and the Ca F2 purity of the sediment,with or without adding the seed crystal of Ca F2. Results showed that( i) in the first stage of precipitation with calcium salt,the optimum conditions were as follows: the p H was adjusted around 9 using a calcium hydroxide solution,and the dosage of the 5% calcium chloride solution was determined according to the mole number of Ca F2( herein,n = 0. 75),stirring for 45 min and precipitating for 90 min,and then( ii) in the second stage of flocculation with PAC,the optimum conditions were as follows: the p H was around 7. 5 and the dosage of PAC was 350 mg / L.Then,the residual mass concentration of fluoride ion in the wastewater could be controlled under 10 mg / L,meeting the first class of Integrated Wastewater Discharge Standard( GB-8978-1996). Besides,in the first stage by adding the seed crystal of Ca F2 with a dosage of 10 g / L,in the sediment the moisture content was found to decrease by 20% while the Ca F2 purity increased up to 85%,which indicates a better fluoride-removal effect and benefits for Ca F2 recovery and reuse.

关 键 词：高含氟废水 CaCl2-PAC工艺 晶种 氟化钙回收 

分 类 号：X703[环境科学与工程—环境工程]