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Catalytic membranes containing metal nano-catalyst are widely used in dye wastewater treatment. Comparing to the traditional catalyst loading methods, such as the co-precipitation, the surface grafting, and impregnation et al., hydrothermal method is simple, and the crystals obtained have a uniform distribution and high purity. In this study, CuO nano-catalysts is immobilized on ceramic substrate by hydrothermal method. The prepared membrane is used to activate persulfate (PMS) for the degradation of azo dyes. FTIR, XPS, XRD, and FESEM characterizations prove that CuO is successfully loaded onto the Al2O3 substrate, the optimal loading amount is 0.03 g/cm2. Static degradation experiments show that the composite membrane could degrade 85% of the Congo red within 80 min. In the dynamic degradation process, the degradation efficiency is further improved to a maximum of 96.8% within 80 min, and the permeation flux of catalytic membrane is relatively stable during the degradation process. In long-term experiments, the degradation efficiency still remains at ~ 87% after 4 cycles, indicating good stability. Quenching experiment shows that the main oxidizing radicals are sulfate radical. In conclusion, the prepared membrane can activate PMS efficiently, which has a potential applications in dye wastewater treatment. [ABSTRACT FROM AUTHOR]

Lipases are widely used in industry. Free lipases are difficult to recover and have poor stability under operational conditions. Herein, lipases are immobilized onto the methyltrimethoxysilane (MTMS)-modified ceramic membranes (~ 5 nm) with reverse filtration method, and further cross-linking by glutaraldehyde (GA) is used to improve the lipase stability. FTIR and XPS analyses demonstrate the successful immobilization of lipase. The immobilized lipases are used to hydrolyze glycerol triacetate (GT) to fatty acids and glycerol. Under the optimal immobilization conditions (MTMS concentration 0.1 M, lipase immobilization time 80 min, lipase concentration 3 mg/mL, and GA concentration 2%), the loading of lipases reaches 0.24 mg/g. Under the optimal operational conditions (temperature 45 °C, pH 7, pressure 0.2 MPa, GT concentration 0.05 M), the immobilized lipases have the highest catalytic activity of 25 U/mg. Moreover, the thermal and pH stabilities of immobilized lipases are found to be higher than those of the free lipases. In the long-term runs, the immobilized lipases still have 64% of the initial activity after 7 cycles, indicating good reusability. This paper provides a simple process for immobilizing lipase on ceramic membranes. The immobilized lipases have better stability at high temperature and basic environments (pH 7–9), which would have broad applications in lipase-catalyzed reactions. [ABSTRACT FROM AUTHOR]

Growing environmental concerns have fueled the need for efficient separation of oil-water mixtures. Membranes that separate oil-water mixture based on contrasting wetting properties have recently received significant attention. Here, hydrophobic and oleophilic ceramic membranes have been successfully prepared for the application of water-in-oil emulsion separation. The membranes were fabricated by modification the ZrO membrane with hexadecyltrimethoxysilane (HDTMS). SEM, EDS, and pore size measurements depict that HDTMS has been grafted onto the ZrO membrane surface without changing the membrane morphology and pore structure. Contact angle measurements confirm that HDTMS modification improves the membrane hydrophobicity and oleophilicity. The modified membrane was thermally stable to 220 °C, and had good chemical stability in a series of organic solvents, even under high-speed scouring. The antifouling performance of the modified membrane was assessed via the filtration of water-in-oil emulsions. The modified membranes showed higher oil flux and higher water rejection compared with the unmodified membranes. The modified membrane can separate all the water droplets from the water-in-oil emulsions. The hydrophobicity of the grafted HDTMS chains was considered to be responsible for reducing the water droplet adsorption on the membrane surface. [ABSTRACT FROM AUTHOR]