Sonochemical oxidation of carbon disulfide in aqueous solutions: Reaction kinetics and pathways

The kinetics of sonochemical oxidation of CS₂ and the effects of process parameters (e.g., concentration, pH, temperature, ultrasonic intensity, irradiation medium, dissolved gas and time, etc.) on the degradation rates and product distributions were studied in a batch reactor at 20 kHz. Sonochemical oxidation was found to decrease with an increase in the solution temperature, and the reaction rate order was dependent on the temperature (T) range studied: zero-order at T ≥ 10°C [with rate constants of (0.66-3.68) × 10^-5 M min^-1] and first-order at T ≤ 5°C (with rate constants of 0.037-0.266 min^-1). From Arrhenius law, k = A exp(E_A/RT), the activation energy, E_A, for the zero-order degradation of CS₂ in the presence of air as the irradiating gas was found to be 7.2 kJ/mol at the higher temperatures compared to 28.7 kJ/mol for the first-order degradation at the lower temperatures. Sonochemical oxidation pathways leading to sulfate formation are discussed. The results of this study suggest that the ultrasonic degradation of CS₂ might provide an environmentally conscious method for the control of this hazardous pollutant in industrial wastewater.