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 Fe²⁺/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 Fe²⁺ and S₂O₈^2- exhibited a noticeable influence on CBZ removal efficiency, where [S₂O₈^2-] exerted more significant effects than that of [Fe²⁺]. The optimal molar ratio of CBZ, Fe²⁺, 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.