Photocatalytic activity of TiO2/SiO2 prepared from silica contained in volcanic ash for ammonia removal

This paper presents a study on the improvement of TiO<inf>2</inf> photocatalytic activity by supporting it on SiO<inf>2</inf> purified from the volcanic ash of the eruption of Merapi Mt. standing in Yogyakarta, Indonesia. The preparation of TiO<inf>2</inf>/SiO<inf>2</inf> was conducted by the sol-gel method at various pH. The photocatalyst prepared were characterized by using XRD, FTIR, SEM, and DRUV spectrometry methods. The photocatalytic activity was examined for ammonia removal. The research results reveal that silica gel from the volcanic ash can be used for supporting TiO<inf>2</inf> photocatalyst to successfully form nanoparticles with anatase type and to enhance its photocatalytic activity in the ammonia removal. The highest activity of TiO<inf>2</inf>/SiO<inf>2</inf> was shown by photocatalyst prepared at pH 4. The ammonia removal was found to be controlled by photocatalysts dose, pH and the UV irradiation time, wherein the maximum ammonia removal (65) from 50 mg/L in 100 mL solution was obtained by applying 50 mg of the photocatalyst dose, at pH 9, and 24 h of time. The ammonia removal was believed through oxidation reaction to form NO<inf>3</inf> ^- ion and/or degradation to form N<inf>2</inf> gas, but it has not been proved yet that needs to be further studied. © 2020 Elsevier B.V., All rights reserved.