地下水中常见离子对纳米零价铁除Se(Ⅳ)动力学的影响

Dynamic Effects of Commonly Co-Existing Anions on the Removal of Selenite from Groundwater by Nanoscale Zero-Valent Iron

采用间歇实验对纳米零价铁(nZVI)除四价硒(Se(Ⅳ))进行实验性研究,考察了地下水中共存离子对nZVI除Se(Ⅳ)动力学的影响.结果表明,在厌氧条件下,当nZVI投加量为0.1 g·L-1,Se(Ⅳ)浓度为100μmol·L-1,NaCl浓度为0.01 mol·L-1,pH=7.0,T=25℃±1℃时,投加CO2-3或SO2-4浓度为1 mmol·L-1、腐殖酸(humic acid,HA)为5 mg·L-1时,明显抑制了Se(Ⅳ)的去除.投加0.5 mmol·L-1Ca2+或Mg2+时,对除Se(Ⅳ)影响不大;而Ca2+(3 mmol·L-1)、Mg2+(3 mmol·L-1)时,Se(Ⅳ)的去除效率明显下降.未加共存离子时,Se(Ⅳ)在20 min时基本去除完,共存离子存在的情况下,nZVI对Se(Ⅳ)的去除率在30 min时达到100%.反应过程中二价铁(Fe2+)随着Se(Ⅳ)的去除趋于平稳.ORP在反应过程中快速从正值下降至负值,由此说明nZVI除Se(Ⅳ)的过程发生了还原反应.

Batch experiments are used to research selenite removal from groundwater by nanoscale zero-valent iron( nZVI),and dynamic effects of commonly co-existing anions on the removal of selenite are also investigated. The results showed that under anoxic conditions,when nZVI dose was 0. 1 g·L- 1,the concentration of Se( Ⅳ) /sodium chloride was 100 μmol·L- 1/0. 01 mol·L- 1,pH = 7. 0,T = 25℃ ± 1℃,auto-adding 1 mmol·L- 1CO2-3or SO2-4,5 mg·L- 1humic acid( HA),the removals of Se( Ⅳ) were obviously inhibited. The weak effect on the removal of Se( Ⅳ) was observed when added 0. 5 mmol·L- 1Ca2 +or Mg2 +,while concentrations of Ca2 +and Mg2 +were 3 mmol·L- 1and 3 mmol·L- 1respectively,removal efficiency of Se( Ⅳ) were evidently decreased. Without coexisting ions,Se( Ⅳ) were totally removed in 20 min,while with co-existing ions,removal efficiency of Se( Ⅳ) were achieved 100% in 30 min. Bivalent iron tended to stationary with the remove of Se( Ⅳ) in reaction processes. ORP rapidly decreased from positive to negative in the process of reaction,which illustrated the process of remove Se( Ⅳ) by nZVI was the reduction reaction.