Heliyon (May 2020)
Natural rubber modification as a pre-vulcanized latex impregnated with TiO2 for photo-catalytic degradation of gaseous benzene
Abstract
Photocatalytic oxidation purposes an economical and environmental friendly process to remove benzene from indoor air pollution. However, the process efficiency is primarily dependent on catalytic-film. The main purpose of this study is to synthesize pre-vulcanized latex impregnated with TiO2 (PVL-TiO2 thin film) from natural rubber to be used in photo-catalytic oxidation for benzene removal in a reactor. PVL-TiO2 thin films were synthesized for 3 different dosages of TiO2, which were 5%, 15%, and 25% The outcome of this study offers the new application of modified natural rubber in terms of environmental and health care protection. Morphology of the synthesized films was analyzed by SEM. The results showed that TiO2 particles could be well dispersed all over the surface of the film, in which the best distribution could be found for the PVL-TiO2 15% thin film. Tensile stress of the films was analyzed using ASTM D412. Results showed that the stress of the films got higher with the increasing amount of TiO2 content. This indicates that TiO2 strengthened the PVL-TiO2 film because the uniformly distribution of TiO2 on the inner surface increased the strength of the film. The decomposition of PVL and PVL-TiO2 thin films was analyzed using thermo gravimetric analysis. The maximum weight loss rates in the range of 1.536–1.145 wt%/°C attained at between 380 - 382 °C TiO2 particles enhanced thermal stability of PVL-TiO2 thin films due to the high decomposition temperature of its properties and also acted as barrier for the heat transfer of the films. Specific surface area (SSA) of the films was analyzed using Brunauer-Emmett-Teller. Specific surface area increased as the increasing content of TiO2, which corresponded to the morphology analysis by SEM. The analysis of chemical functional group of thin films was performed using ATR-FTIR. The results of Crystal identification using XRD clearly showed good attachment of rutile TiO2 on the films. Finally, results of absorbance spectrums and band gap energy showed that PVL not only peg TiO2 particles but also reducing band gap energy which induced by S and ZnO. Therefore, PVL-TiO2 thin films could be used under visible light condition. The films were then used in the study of benzene removal in annular reactor. The highest removal efficiency (83%)for the PVL-TiO2 15% thin film was obtained. Comparing to the maximum removal efficiency for PVL film (28%), roughly 60% increase in efficiency was achieved. The PCO kinetics were well fit by a first order Langmuir-Hinshelwood model. The calculation of oxidation rate and percentage of residual intermediates indicated that accumulation of residual intermediates can occur on the active site and the gas phase, resulting in increasing of residual intermediates. The successful synthesis of PVL-TiO2 thin film provides new opportunity to use natural rubber in terms of environmental and health care protection.
