Ceramic Membranes Prepared from a Silicate and Clay-mineral Mixture for Treatment of Oily Wastewater

The application of ceramic membranes is limited by the high cost of raw materials and the sintering process at high temperatures. To overcome these drawbacks, the present study investigated both the preparation of ceramic membranes using cost-effective raw materials and the possibility of recycling the membranes for the treatment of oily wastewater. Ceramic membranes with a pore size of 0.29–0.67 μm were prepared successfully at temperatures as low as 1000–1100°C by a simple pressing route using lowcost base materials including diatomite, kaolin, bentonite, talc, sodium borate, and barium carbonate. The typical steady-state flux, fouling resistance, and oil-rejection rate of the low-cost virgin membranes sintered at 1000°C were 2.5 × 10−5 m3m−2s−1 at 303 kPa, 63.5%, and 84.1%, respectively, with a feed oil concentration of 600 mg/L. A simple burn-out process of the used membranes at 600°C in air resulted in >95% recovery of the specific surface area (SSA) of the virgin membranes, a significantly increased steady-state flux, decreased fouling resistance, and increased oil-rejection rate. The typical steady-state flux, fouling resistance, and oil-rejection rate of the low-cost ceramic membrane sintered at 1000°C and subsequently heat treated at 600°C for 1 h in air after the first filtration were 5.4 × 10−5 m3m−2s−1 at 303 kPa, 27.1%, and 92.9%, respectively, with a feed oil concentration of 600 mg/L. The present results suggest that the low-cost ceramic membranes used for oily wastewater filtration can be recycled by simple heat-treatment at 600°C in air. As the fouling resistance of the low-cost ceramic membranes decreased with a decrease in pore size, the preferred pore size of the membranes for oily wastewater filtration is <0.4 μm.