Abstract
Rhodamine B is a non-biodegradable organic pollutant that is difficult to decompose by microorganisms. If it is possible to be degraded it will take a long time. The semiconductor used is ZnO using SiO2 host material. The reason for using SiO2 is that apart from high efficiency, there are also abundant raw materials because the eruption of Mount Merapi occurs regularly every 4 years. The high content of SiO2 in volcanic ash can be utilized and processed into silica gel through the formation of potassium silicate resulting from the reaction between SiO2 in volcanic ash and potassium hydroxide. In addition to the presence of abundant SiO2, ZnO sources from lathe workshop waste are also easily obtained. The manufacture of ZnO/SiO2 nanocomposites was carried out using the sol – gel method because it is easy and has high effectiveness. ZnO/SiO2 nanocomposite was applied as an adsorbent to degrade Rhodamine B. This study aims to determine the character of ZnO/SiO2 nanocomposite and to determine the best conditions for optimal degradation. Synthesis of ZnO/SiO2 nanocomposite based on volcanic ash and zinc waste resulted in a composite size with a size range of 100-200 nm and a uniform circular shape. The results of the FTIR test show that SiO is at a wavelength of 993.34 and 1109.07 cm-1, while ZnO is at a wavelength of 443.63 cm-1. The XRD results of ZnO/SiO2 nanocomposite are known to peak at 2𝜃, namely 30.42o, 31.56o, and 44.40o. The application of dye degradation on UV irradiation, as well as looking for pH, time, and concentration gave the maximum Rhodamine B degradation value. The results of this study indicate that the highest efficiency in decreasing the concentration of Rhodamine B was obtained at pH 3 with a contact time of 60 minutes and a concentration of Rhodamine B of 10 ppm. The degradation efficiency of Rhodamine B obtained under these conditions is 95.8690%. Based on the concentration variation data processing using the Langmuir isotherm equation, it is known that the adsorption capacity of Rhodamine B is 97.3458521%.