Degradation of carbamazepine by Fe(II)-activated persulfate process

Experimental studies were conducted to investigate the oxidative degradation of carbamazepine (CBZ), one of the most frequently detected pharmaceuticals in various waters, by Fe(II)-activated persulfate process. Results show that the Fe(2+)/S2O8(2-) process is very effective for the elimination of CBZ and characterized by a two-stage kinetics (a rapid initial decay followed by a retardation stage). CBZ degradation reaction was observed to be pH dependent and the optimum pH is 3.0 in the range of 2.00-7.87. The concentration of Fe(2+) and S2O8(2-) exhibited a noticeable influence on CBZ removal efficiency, where [S2O8(2-)] exerted more significant effects than that of [Fe(2+)]. The optimal molar ratio of CBZ, Fe(2+), and S2O8(2-) is found to be 1:5:40. The effect of various inorganic anions on CBZ removal was also evaluated under the optimal conditions. The anions NO3(-), SO4(2-) and H2PO4(-)caused a negative effect on the performance of this process, while Cl(-) interestingly accelerated CBZ degradation. The higher the Cl(-) concentration, the faster the CBZ decay rate. The intermediates were identified during CBZ degradation with and without the presence of Cl(-). The evolution of intermediates for these two scenarios was compared. The decay pathways of CBZ were proposed accordingly.