Enhanced photocatalysis of natural rubber foams filters boosted by modified-titanium oxide hybrid fillers: Gaseous benzene removal, antibacterial properties and air permeability

Natural rubber (NR) composite foam was developed through the Dunlop process with better volatile solvent ab- sorption and antibacterial activity. The unmodified and modified titanium dioxide (TiO2), namely TiO2-zinc oxide (TiO2- ZnO) and TiO2-silver doped zirconium (TiO2-Ag-Zr), were incorporated into the foams. The photocatalytic origination under UV and visible light leads the composite foam with TiO2-ZnO to exhibit effective and suitable benzene absorbing and re- moving abilities. Thus, the specific foam sizes provided the gaseous benzene absorption of 14.0 ppm within 3 h and the gaseous benzene elimination of 7.6 ppm within 14 h in case of the composite with 10 phr TiO2-ZnO. Also, the foams with NR/TiO2-ZnO and NR/TiO2-Ag-Zr exhibited excellent antibacterial activity for E. coli due to the release of Zn+ and ROS species across the rubber foam filter layers to the bacteria surfaces. The resulting composite foam showed superior elastic properties in terms of tensile strength, toughness, and elongation at break. To study the applicability as filter, the engineering simulation relating the air flowability throughout the foam was examined. From the flow velocity and the air permeability of the foam at a specified thickness, it was observed that the NR/TiO2-ZnO exhibited proper porous sizes and shapes for fil- trating, reacting, absorbing and removing the gaseous benzene relative to other porous filters.