Synergistical enhancement by Ni2+ and Tween-80 of nanoscale zerovalent iron dechlorination of 2,2′,5,5′-tetrachlorinated biphenyl in aqueous solution

Effective dehalogenation by nanoscale zerovalent iron (nZVI) has been reported. In this study, the effects of Ni2+, Cu2+ ions, and the nonionic surfactant Tween-80 on dechlorination of 2,2', 5,5'-tetrachlorinated biphenyl (PCB-52) by nZVI were investigated in aqueous solution. The rate of dechlorination was significantly enhanced by Ni2+, while Cu2+ had a less significant catalytic effect. Ni2+ and Tween-80 used in combination synergistically enhanced dechlorination of PCB-52 by nZVI, although the enhancement by Tween-80 was inhibitory in the presence of Cu2+ and insignificant in the absence of both metal ions. Congener specificity in the dechlorination pathway resulted from the preferential retention of ortho-chlorine, which restricted the formation of environmentally toxic coplanar PCB congeners. The application of nZVI dehalogenation enhanced by Ni2+ and Tween-80 is a promising technique for posttreatment of PCB-contaminated soil washing solutions.