Influence of Salts on the Photocatalytic Degradation of Formic Acid in Wastewater

Abstract

Conventional wastewater treatment technologies have difficulties in feasibly removing persistent organics. The photocatalytic oxidation of these contaminants offers an economical and environmentally friendly solution. In this study, TiO2 membranes and Ag/TiO2 membranes were prepared and used for the decomposition of dissolved formic acid in wastewater. The photochemical deposition of silver on a TiO2 membrane improved the decomposition rate. The rate doubled by depositing ca. 2.5 mg of Ag per 1 g of TiO2. The influence of salinity on formic acid decomposition was studied. The presence of inorganic salts reduced the treatment performance of the TiO2 membranes to half. Ag/TiO2 membranes had a larger reduction of ca. 40%. The performance was recovered by washing the membranes with water. The anion adsorption on the membrane surface likely caused the performance reduction.

Performance of TiO2-Based Tubular Membranes in the Photocatalytic Degradation of Organic Compounds

“…The presence of silver was confirmed in earlier re through X-ray photoelectron spectroscopy (XPS) analysis [43]. Further characteris of the membranes can be found in previous publications [41,43]. 220) and (215) crystallographic planes belonging to the anatase phase with tetragonal structure, respectively [45][46][47].…”

“…The immobilisation of TiO 2 on ceramic tubes did not significantly affect the TiO 2 phases, since the annealing temperature used in this study, 673 K, is lower than the temperature that causes anatase to transition to rutile. The presence of silver was confirmed in earlier research through X-ray photoelectron spectroscopy (XPS) analysis[43]. Further characterisations of the membranes can be found in previous publications[41,43].…”

“…The presence of silver was confirmed in earlier research through X-ray photoelectron spectroscopy (XPS) analysis[43]. Further characterisations of the membranes can be found in previous publications[41,43].…”

“…The colour of the membrane changed from white to light yellow after UV irradiation. Under these conditions, silver can be deposited as metallic silver and silver oxide [43].…”

“…Some of the TiO2 membranes were immersed in a acetate solution and exposed to UV light. The concentration of silver in the soluti creased due to photoreduction, because silver ions were photochemically reduced o The colour of the membrane changed from white to light yellow after UV irradiatio der these conditions, silver can be deposited as metallic silver and silver oxide [43]. 116), ( 220) and (215) crystallographic planes belonging to the anatase phas tetragonal structure, respectively [45][46][47].…”