Study of solar photocatalytic degradation of Acesulfame K to limit the outpouring of artificial sweeteners

In this study, the photocatalytic degradation of an artificial sweetener, Acesulfame K (ACK), has been investigated with TiO2 photocatalyst using a solar simulator. Adsorption of ACK on TiO2 surface follows Freundlich adsorption isotherm in the pH range of 6-8 and shows an adsorption coefficient of 0.002 L/mg. Parametric studies for solar photocatalytic degradation are performed varying initial concentrations of ACK, photocatalyst dosage, and solar light intensity. Photocatalytic degradation rate of ACK gradually decreases with increasing initial concentration of ACK, and the rate follows pseudo first-order kinetics. The degradation rate of ACK gradually increases as the TiO2 dosage is increased and reaches maximum at 0.8-1.0 g/L. The rate constant for ACK degradation has been found to be directly proportional to light intensity, obeying a power law model. Complete degradation of ACK for 10-20 mg/L initial concentration is observed within the first 30 min of solar light irradiation of 100 mW/cm2 at pH 6. Complete mineralization of ACK can be achieved in 6 h with dissolved organic carbon (DOC) less than 1 mg/L. Complete mineralization of ACK and its by-products is successfully achieved with an apparent quantum yield of 0.02% at 1 sun thus making the process sustainable. This study manifests the efficacy of the solar photocatalytic process on degrading emerging pollutants like ACK where the use of artificial UV lamp has successfully been substituted by solar light, the most abundantly found sustainable source of energy in nature. Moreover, the process followed in this study is devoid of the use of any hazardous chemicals.