Nanofiltration performance of SiO2-ZrO2 membranes in aqueous solutions at high temperatures

• Nanofiltration performance of SiO2-ZrO2 membranes was evaluated at high temperature.
• Water permeability increased and reached a stable value after 4 h treatment at 90 °C.
• Water permeability and rejection were stable after treatment at 90 °C for 100 h.
• SiO2-ZrO2 membranes fired at 550 °C showed excellent hydrothermal stability.

Nanofiltration performance at high temperatures was examined using SiO2-ZrO2 membranes fired at 200 and 550 °C. After SiO2-ZrO2 membranes were treated in water at 90 °C for 4 h, the water permeability (Lp) at 25 °C for both membranes increased approximately 3-fold and remained constant for as long as 100 h treatment, indicating stability in aqueous solutions as high as 90 °C. The increase in water permeability of membrane was ascribed to increased hydrophilicity and dissolution of silica into water at 90 °C. Molecular weight cut-offs (MWCOs) for SiO2-ZrO2 membrane fired at 550 °C did not change with treatment time (MWCOs = 300) while the MWCOs for SiO2-ZrO2 membrane fired at 200 °C increased from 240 to 300. SiO2-ZrO2 membranes fired at 550 °C showed higher hydrothermal stability than those fired at 200 °C.The effect of temperature on SiO2-ZrO2 membrane performance was evaluated for nanofiltration at temperatures range of 25–90 °C. The rejection of glucose and maltose decreased with an increase in temperature for SiO2-ZrO2 membranes both fired at 200 and 550 °C, while the permeate flux increased. On the other hand, the temperature has no influence on rejection of raffinose, which was always larger than 95%.

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