不同pH条件下As还原对砷释放的影响实验研究

通过考察不同pH条件下Fe(Ⅲ)-A(sⅤ)体系和Fe(Ⅲ)-As(Ⅲ)体系各Fe形态、As形态、以及体系ORP的变化,考察不同pH条件下As还原对砷释放的影响。实验结果表明:在pH为3⁵左右范围内,Fe(Ⅲ)-A(sⅤ)体系和Fe(Ⅲ)-A(sⅢ)体系中的Fe(Ⅲ)均发生部分絮凝沉淀,在水样pH为65左右范围内,Fe(Ⅲ)-A(sⅤ)体系和Fe(Ⅲ)-A(sⅢ)体系中的Fe(Ⅲ)均发生部分絮凝沉淀,在水样pH为6¹0范围内,Fe(Ⅲ)-As(Ⅲ)体系中Fe(Ⅲ)的絮凝沉淀较Fe(Ⅲ)-As(Ⅴ)体系明显。Fe(Ⅲ)-As(Ⅴ)体系与Fe(Ⅲ)-A(sⅢ)体系中As总随pH的变化趋势基本一致,但是Fe(Ⅲ)-A(sⅢ)体系As总的浓度水平要比Fe(Ⅲ)-A(sⅤ)体系的浓度水平要高。结果表明:同等pH环境条件下,如果A(sⅤ)被还原成A(sⅢ),则Fe(Ⅲ)-As体系中就会出现As的释放,且不同pH条件下对应的As总的差值即可反映出当A(sⅤ)还原成A(sⅢ)时Fe(Ⅲ)-As体系中所释放的砷的量。

Experimental Study on Effect of Reduction of Arsenic on Arsenic Release under Different pH Conditions

Through investigating the change with time of each iron speciation,arsenic speciation and ORP of system under different pH conditions between Fe(Ⅲ)-As(Ⅴ)system and Fe(Ⅲ)-As(Ⅲ)system,the effect of the reduction of arsenic on arsenic release under different pH conditions was studied.Results indicated that within pH range of about 3~5,Fe(Ⅲ)in Fe(Ⅲ)-As(Ⅴ)system and Fe(Ⅲ)-As(Ⅲ)system both hydrolyzed partially,while within pH range of 6~10,flocculation and precipitation degree of Fe(Ⅲ)of Fe(Ⅲ)-As(Ⅲ)system was more obvious than Fe(Ⅲ)-As(Ⅴ)system.The change trend with pH of total arsenic concentration of Fe(Ⅲ)-As(Ⅲ)system was basically consistent with Fe(Ⅲ)-As(Ⅴ)system,but whole concentration level of total arsenic concentration of Fe(Ⅲ)-A(s Ⅲ)system was higher than Fe(Ⅲ)-A(s Ⅴ)system.Arsenic release would appear in Fe(Ⅲ)-As system if A(s Ⅴ)was reduced to A(s Ⅲ)under equal pH condition and corresponding difference value of total arsenic concentration between Fe(Ⅲ)-A(s Ⅴ)system and Fe(Ⅲ)-A(s Ⅲ)system under different pH condition could show the quality of arsenic released from Fe(Ⅲ)-As system when A(s Ⅴ)was reduced to As(Ⅲ).