Antibacterial properties of photochemically prepared AgTiO2 membranes

Biofouling reduces the membrane performance and has become a problem in many applications. One of the strategies to reduce biofouling is to apply antibacterial materials to the membrane surface, which prevents the attachment and growth of microorganisms. In this study, the surface of flat ceramic supports was covered with TiO2 powder, and silver was applied by photoreduction using a CH3COOAg solution at room temperature. After the photoreduction, AgOx and metallic silver were found on the TiO2 as analyzed by XPS. While a negligible amount of silver was released from the prepared AgTiO2 membranes into water, the dissolution of silver was enhanced in a 0.09 M NaCl solution. The AgTiO2 membranes inhibited the growth of Escherichia coli in dark conditions. The inhibition cannot be explained only by the concentration of silver ions released from the membranes. Microscopic observation showed that direct contact with AgTiO2 kills E. coli. The results showed the possibility of improving the antibacterial activity of membranes by applying an AgTiO2 coating

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

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

Catalytic surface modification of alumina membrane for oxygen separation

Two types of alumina ceramic membrane in hollow fibre shape was used in this study. Both alumina hollow fibres (AHF) were sintered at different temperatures; (a) 1350oC and (b) 1450oC. In order to improve the catalytic activity of the alumina membrane for oxygen separation purposes, surface modification of the membranes was carried out using La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) perovskite catalyst. LSCF was synthesised using simple Pechini sol-gel method. The evaporation time and temperature of the LSCF-sol were varied to obtain various viscosity of catalytic sol. From XRD analysis, pure LSCF perovskite structure formed at temperature at 850oC. The morphological of unmodified and surface-modified alumina hollow fibre membranes (AHF) were studied using FESEM. The effect of LSCF catalytic sol viscosity was studied and it was found that as the viscosity of the sol increases, the amount of catalyst deposited on the alumina hollow fibre were increased. Besides, the amount of catalyst deposited on 1350 AHF was found to be higher than 1450 AHF. This result is supported by the result of pore distribution data whereby 1350 AHF was observed to be more porous than 1450 AHF, with porosity percentage of 40.38% and 28.80%, respectively. Although higher viscosity of catalytic sol could lead to a high amount of catalyst deposited on the AHF substrate, there is a tendency for micro-cracks to develop. Thus, the viscosity of the catalytic sol is important to control in order to have higher oxygen permeation flux