分步沉淀法去除稀土废水中钙镁的研究  

Study on Removal of Calcium and Magnesium in Rare Earth Wastewater by Stepwise Precipitation

作　　者：黎新[1,2] 孙长顺 赵建军[1,2] 靳晓春 陆强 

机构地区：[1]陕西省环境科学研究院,710061 [2]长安大学,710054 [3]陕西华陆化工环保有限公司,陕西西安710077

出　　处：《水处理技术》2016年第7期88-92,共5页Technology of Water Treatment

摘　　要：稀土酸法冶炼过程中会产生含有Ca^(^(2+))、Mg^(2+)的硫铵废水,为了减少结垢对蒸发或膜法处理工艺的影响,采用分步沉淀法去除钙镁,即在废水中先后加入草酸和磷酸盐,分别得到草酸钙和磷酸铵镁沉淀,研究了pH、沉淀剂投加量、陈化时间及晶种加入量对钙镁去除效果的影响。结果表明,除钙阶段的最佳反应条件为:晶种(草酸钙)加入量为1.5‰,pH=7.5,n(H_2C_2O_4):n(Ca^(2+))=1.2:1,搅拌陈化2 h,Ca^(2+)去除率达到92.2%,此时的Mg^(2+)浓度几乎没有变化;对除钙后废水进行MAP法除镁处理的最佳反应条件为:pH=7.5,n(NH_4H_2PO_4):n(Mg^(2+))=0.9:1,搅拌陈化2 h,Ca^(2+)去除率达到81.8%,Mg^(2+)去除率达到98.1%;X衍射结果表明沉淀物分别为较为纯净的CaC_2O_4和MgNH_4PO_4·6H_2O。The rare earth wastewater contains large amounts of Ca2＋ and Mg2＋. In order to reduce the effect of evaporation or membrane fouling treatment process, this experiment adopts the method of stepwise precipitation for calcium and magnesium removal, namely adding oxalic acid and phosphate successively to the wastewater, producing calcium oxalate and magnesium ammonium phosphate precipitation respectively, mainly studied pH value, dosage of precipitation agent, aging time and seed amount how to affect the removal efficiency of the calcium and magnesium. The results showed that, the optimum condition of CAC2O4 precipitate was seed （calcium oxalate） amount = 1.5 per thousand, pH=7.5, n（H2C2O4）：n（Ca2＋）=1.2：1, aging time was 2 hours, the removal ratio of Ca2＋ reached 92.2%, at this time, the concentration of Mg2＋ was almost unchanged; the optimum condition of MAP precipitate was pH=7.5, n（NH4H3PO4）：n（Mg2＋）=0.9：1, aging time was 2 hours, the removal ratio of Ca2＋ reached 81.8%, and the removal ratio of Mg2＋ reached 98.1%; the sediments were CAC2O4 and MgMH4O4·6H2O by X-ray diffraction.

关 键 词：分步沉淀 稀土废水 钙镁去除 MAP 

分 类 号：X703.1[环境科学与工程—环境工程]