Sonocatalytic degradation of carbamazepine and diclofenac in the presence of graphene oxides in aqueous solution

Abstract

This research investigated the removal of carbamazepine (CBZ) and diclofenac (DCF) in water using ultrasonic (US) treatment in the absence or presence of graphene oxides (GOs). Three frequencies and three pH conditions were tested (28, 580, and 1000 kHz and 3.5, 7, and 9.5, respectively). Regarding the effects of US frequency and pH, 580 kHz and pH 3.5 were more effective at removing CBZ and DCF (>86% for CBZ and >92% for DCF) than 1000/28 kHz and pH 7/9.5 within 60 min. However, sonocatalytic removal was enhanced in the presence of GOs; more than 99% CBZ and DCF removal was achieved at 580 kHz and pH 3.5 within 40 min. The sonicated GOs were more stable at 28 kHz than at higher frequencies of 580 and 10,00 kHz. The adsorption of CBZ and DCF has increased when GOs were sonicated at 28 kHz (44% and 61%, respectively) compared with 580 kHz (34% and 52%, respectively) and 1000 kHz (18% and 39%, respectively). The negative charges of GOs increased at 28 kHz (−105.1 mV), however, it decreased at higher frequencies such as 580 kHz (−71.5 mV) and 1000 kHz (−58.6 mV), which led to increased electrostatic repulsion that increased the stability of the GO particles in water. The overall enhancement in CBZ and DCF removal was due to an increase in cavitational bubbles, which in turn led to increased production of OH• and enhanced adsorption due to dispersion (resulting from US irradiation), which caused an increase in active adsorption sites of the GOs.