硫酸钛混凝去除无机砷(Ⅲ)的效能

Removal efficiency of As(Ⅲ) by titanium sulfate coagulation

使用硫酸钛作为混凝剂,研究了混凝去除As(III)过程中溶液p H值、混凝剂投加量、砷的初始浓度以及阴离子对除砷效果的影响。硫酸钛的水解沉淀物颗粒等电点为p H=5;当p H=6时,水解沉淀物的粒径最大。在p H=5~8范围内,As(III)的去除率高且基本稳定;而沉淀物颗粒Zeta电位降低较大。说明水解沉淀物Zeta电位对As(III)的去除影响不大。混凝剂投加量为2.5~10 mg/L时,As(III)的去除率随投加量的增加而显著增加;混凝剂投加量大于15 mg/L时,As(III)去除率随混凝剂投加量的增加变化趋于平缓。水中阴离子(硅酸根和磷酸根离子)的存在会降低混凝对As(III)的去除效率。

The influences of solution p H,coagulant dosage,initial arsenite concentration,and the presence of silicate and phosphate on removal of arsenite in water by coagulation of titanium sulfate were investigated.The isoelectric point( IEP) of titanium sulfate was found to be at p H 5; the maximum hydrolytic precipitate size of titanium sulfate occurred at p H = 6. In the p H range from 5 to 8,As( III) removal efficiency reached the maximum and was relatively stable; while the zeta potential of the precipitates decreased significantly. This indicates that zeta potential has only negligible effect on the As( III) removal in the coagulation process. As the coagulant dosage increased from 2. 5 to 10 mg / L,As( III) removal efficiency increased significantly. However,above the coagulant dosage of 15 mg / L,only a slight increase in As( III) removal was observed as the coagulant dosage further increased. The presence of silicate and phosphate decreased the As( III) removal efficiency by coagulation of titanium sulfate.