Photocatalytic degradation of formaldehyde in aqueous solution using ZnO nanoparticles immobilized on glass plates

In the present study, the application of a photocatalytic process equipped with immobilized ZnO nanoparticles on glass plates was studied for removing formaldehyde in an aqueous phase. According to the obtained data, the removal efficiency of formaldehyde was sharply decreased to 12.96% as the solution experienced strong acidic conditions (pH 2). In addition, the removal efficiency was decreased from 56.41 to 44.02% with increasing pH values from 7 to 10, respectively, indicating a considerable drop in the removal efficiency at basic conditions. As the initial concentration of formaldehyde fed into the reactor was increased from 500 to 4000 mg/L, its removal efficiency decreased from 62.30 to 11.96%, respectively, in a short time of 30 min. The obtained removal efficiency of chemical oxygen demand (41%) demonstrated a considerable mineralization of formaldehyde along with a removal efficiency of 56.41%. The kinetic study was performed and the result indicated a significant reaction rate of the photocatalytic degradation of formaldehyde (k_app = 0.0265 l/min), resulting in a removal efficiency of 96.08% by 120 min at an initial formaldehyde concentration of 1000 mg/L. It can be concluded that the photocatalytic process using immobilized ZnO nanoparticles could be an efficient and promising method for treating wastewaters containing formaldehyde.