Interaction between pollutants during the removal of polychlorinated biphenyl-heavy metal combined pollution by...

Modified nanoscale zero-valent iron (nZVI) is a promising functional material for the remediation of combined pollutants involving polychlorinated biphenyls (PCBs) and heavy metals. However, the interaction between the two types of pollutants has not been systematically studied for this method of treatment. In this study, 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153), Cu²⁺, and Ni²⁺ were selected as the target pollutants. To understand the interaction between pollutants, the efficiencies of nZVI, sulfidated nZVI (S-nZVI), and carboxymethylcellulose stabilized nZVI (CMC-nZVI) were investigated for removal of PCB153, Cu²⁺/Ni²⁺, and combined pollution system (PCBs-Cu²⁺/Ni²⁺). Results showed that the removal kinetics of the two types of pollutants by the three materials fitted a pseudo-first-order model well and that the reaction mechanisms were similar. Among the three materials, CMC-nZVI showed the highest reactivity to degrade PCB153 (pseudo-first-order kinetic constants (k_obs) = 2.7 × 10^-4 min^-1) and remove Cu²⁺ (k_obs = 2.890 min^-1), while S-nZVI showed higher affinity for the removal of Ni²⁺ (k_obs = 0.931 min^-1). For the combined pollution system, PCB153 had little effect on the removal of heavy metals by the three materials, while the effect of heavy metals on PCB153 degradation was related to the types of heavy metals and the materials. Cu²⁺ had no significant effect on PCB153 degradation by the three materials, while the coexistence of Ni²⁺ promoted PCB153 degradation by nZVI and CMC-nZVI. XPS and electrochemical analysis showed that Cu⁰ and Ni⁰ were produced on the surface of the three materials. Ni is a more effective catalyst and promoted the electron transfer efficiency of the materials and had a positive impact on the dechlorination reaction.