In this study, batch experiments were conducted to examine vanadium (V) species and environmental factors on the homogenous activation of persulfate (PS) by vanadium ions for the degradation of PCBs (PCB28). The experimental results showed that both V(V) and V(IV) ions activated PS to effectively degrade PCB28. Even with a relatively low V ion concentration (0.01 mM), P0328 was efficiently degraded. The addition of model humic substances (HS) including gallic acid (GA), caffeic acid (CA), protocatechuic acid (PA) and humic acid (HA) facilitated PS activation and PCB28 degradation in the V(V)/PS system, and the pseudo-first order reaction rate constants (k(obs)) of PCB28 were increased 0.4-4.3 times; however, an excess of HS inhibited PCB28 degradation due to quenching reactions between HS and free radicals. Furthermore, higher pH favors PS activation and PCB28 degradation in the presence of GA, CA and PA. All underlying mechanisms of this process were elucidated by the analysis of V(V) species and free radical conversion via electron paramagnetic resonance (EPR) technique. Both Fe(III) and Fe(II) ions were beneficial for PS activation in the V(V)/PS system. Compared with other traditional transition metal activators such as Fe(II), Fe(III), Cu(II), Mn(II) and Ag(I), V(IV) and V(V) were more efficient activators of PS for PCB28 degradation. This study elucidates new metal species for activating PS to degrade contaminants. In addition, this study also explores key factors affecting the remediation efficiency of soil based on PS activation with V species. (C) 2017 Elsevier B.V. All rights reserved.