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.

Low-cost ceramic membrane bioreactor: Effect of backwashing, relaxation and aeration on fouling. Protozoa and bacteria removal.

Membrane biological reactors (MBR) constitute an alternative to conventional wastewater treatments for improved recovery, reuse, and recycling of water. MBRs have a smaller footprint, provide better biotreatment and achieve a high-quality effluent. This work analyses the use of MBRs innovative low-cost ceramic membranes for wastewater treatment. We propose low-cost ceramic membranes as an alternative to the more expensive commercial ceramic membranes. Low-cost membranes were made of clay, calcium carbonate, potato starch, almond shell and chamotte. We synthesized two different selective layers, from clay and/or TiO2. We characterized the membranes (pore diameter and water permeance) and their performance in a laboratory scale MBR. To mitigate membrane fouling and preserve the continued operation along time, the effect of different operating cycles was measured, considering two physical cleaning strategies: relaxation and backwashing. Cycles of 9 min of operation, 30 s of relaxation and 1 min of backwashing provided the lowest fouling rate. We investigated the effect of air scouring on fouling by operating with different air flow rates. Once experimental conditions were optimized, the overall performance of the different ceramic membranes was tested. The membrane with a TiO2 thin layer provided the best resistance to fouling, as well as a good retention capacity of E. coli, Cryptosporidium oocysts and Giardia cysts.

Electrochemical Degradation of Reactive Black 5 using two-different reactor configuration.

Novel Sb-doped SnO2 ceramic electrodes sintered at different temperatures, are applied to the degradation of Reactive Black 5 in both divided and undivided electrochemical reactors. In the undivided reactor the discoloration of the solution took place via the oxidation of RB5 dye, without the corresponding reduction in the chemical oxygen demand for the ceramic electrodes. However, in the divided one, it was possible to achieve the discoloration of the solution while at the same time decreasing the chemical oxygen demand through the ·OH-mediated oxidation, although the chemical oxygen demand degradation took place at a slower rate.

Improvement in Char Strength with an Open Cage Silsesquioxane Flame Retardant.

Different characterization techniques were used to study the hydrolysis and condensation reaction kinetics of 3-methacryloxypropyltrimethoxysilane (MAPTMS) to obtain open cage silsesquioxane oligomers. The formation of hydrogen bonds, which condition the chemical structures of the resulting products, was identified. Improved thermal and fire resistant behavior of unsaturated polyester (UP) composites prepared with aluminium trihydroxide (ATH) and the synthesized oligomer were registered. Opened silsesquioxane structures also showed an improvement in the mechanical properties of the char formed after firing.

Thermal Degradation Mechanism of a Thermostable Polyester Stabilized with an Open-Cage Oligomeric Silsesquioxane.

A polyester composite was prepared through the polymerization of an unsaturated ester resin with styrene and an open-cage oligomeric silsesquioxane with methacrylate groups. The effect of the open-cage oligomeric silsesquioxane on the thermal stability of the thermostable polyester was studied using both thermogravimetric analysis and differential thermal analysis. The results showed that the methacryl oligomeric silsesquioxane improved the thermal stability of the polyester. The decomposition mechanism of the polyester/oligomer silsesquioxane composite was proposed by Fourier transform infrared spectroscopy (FTIR) analysis of the volatiles.