双水相体系萃取分离电镀废水中镉缔合物

Extraction and Separation of Cd^(2+) Complexes in Electroplating Wastewater by Two-Phase Systems Containing Iodide and Ethyl Violet in the Presence of (NH_4)_2SO_4

电镀镉废水直接排放会造成严重环境污染。利用Cd(Ⅱ)与乙基紫(EV)、KI缔合后,加入盐析剂丙醇-水双水相体系萃取分离镉。试验表明,在(NH4)2SO4存在条件下,无表面活性剂EV,在一定量碘离子的酸性条件下,Cd(Ⅱ)的萃取率只有68%,而同样条件下,加入毫克级用量的EV后,Cd(Ⅱ)被完全萃取分离。在pH值为1.0时,试验了Fe(Ⅲ)、Co(Ⅱ)、Ni(Ⅱ)、Zn(Ⅱ)、Mn(Ⅱ)、Cr(Ⅲ)等离子的二元或多元离子混合干扰情况,结果表明分离完全。

A two-phase system of n-propyl alcohol and water containing iodide and ethyl violet was used for the extraction and separation of Cd2+ complexes in electroplating wastewater,based on the complexing reaction between Cd2+ and iodide and ethyl violet in the presence of(NH4)2SO4.The separation efficiency was investigated.It was found that the charged complex compound CdI42-was able to form ion-associated complex with ethyl violet(0.40 mL,concentration 5.0 mol/L)in the presence of(NH4)2SO4 at a proper concentration and was easily extracted into the n-propyl alcohol phase,making it feasible to completely separate Cd2+ fromFe3+,Co2+,Ni2+,Mn2+,Zn2+,and Cr3+.However,under the same conditions but in the absence of ethyl violet,the Cd2+ was separated only at a rate of 68%.