Application of enhanced nZnO photocatalytic process with ultrasonic wave in formaldehyde degradation from aqueous solution

Abstract

This study was performed to evaluate formaldehyde degradation ratio in a batch reactor. For investigation of the synergism effect, formaldehyde degradation by each process (UV photolysis, ZnO catalyst, ultrasonic wave) was tested. In the next step, the influence of important operational parameters, such as pH of the solution (3–8), initial CH2O concentration (20–100 mg/l), dosage of nZnO (10–60 mg/l), ultrasonic wave power (40–150 W), and reaction time (10–60 min) was investigated. Ultrasonic wave process could slightly degrade CH2O and had a partial effect as synergism on formaldehyde degradation. Maximum formaldehyde removal ratio occurred with a nZnO dosage of 60 mg/l, pH of the solution of 8, ultrasonic wave power of 40 W, and initial formaldehyde concentration of 50 mg/l with a contact time of 30 min (78%). A comparison of the reaction orders of kinetic studies showed that formaldehyde degradation was in accordance with pseudo-second-order reaction. It could be found that the sonophotocatalytic process may be recommended for the treatment of solutions containing low formaldehyde concentrations.