Performance and Mechanism Study of Simultaneous Removal of Carbamazepine and Ammonia from Water Using UV/Peroxymonosulfate Process

Wastewater involving nitrogen-containing emerging contaminants is always accompanied by ammonia nitrogen. In this study, the 254 nm UV light activating peroxymonosulfate (PMS) process was investigated based on its performance and mechanisms for the simultaneous removal of carbamazepine (CBZ) and ammonia nitrogen. The results showed that both CBZ and ammonia could be simultaneously removed from water by the UV/PMS process, which was mainly attributed to the oxidation of SO4•− and •OH, respectively. Solution pH did not significantly affect CBZ degradation, but was a crucial factor for the removal of ammonia, and only the alkaline condition was effective for ammonia removal. The steady-state concentration of SO4•− (4.37 × 10−11 M) at pH 10.5 was determined as 32 times that of •OH (1.35 × 10−12 M), which made CBZ more competitive than ammonia in competing for radicals and more adaptable to coexisting anions. An appropriate increase in PMS concentration and light intensity could improve the removal of ammonia more significantly than that of CBZ, but an over-intense reaction could accelerate the decrease in solution pH, resulting in a plateau in ammonia removal. Moreover, the formation of nitrate and nitrogen gas was the primary transformation route of ammonia in the UV/PMS process. With the optimum PMS concentration of 2 mM, about 50% of the total nitrogen could be removed. The results of this study may provide some insights into applying the UV/PMS process for the simultaneous removal of emerging contaminants and ammonia nitrogen.