Processing of alumina-coated clay-diatomite composite membranes for oily wastewater treatment

Crack-free alumina-coated clay-diatomite composite membranes were successfully prepared by a simple pressing and dip-coating route using inexpensive raw materials at a temperature as low as 1000 °C in air. The changes of porosity, flexural strength, pore size, flux, and oil rejection rate of the membranes were investigated while changing the diatomite content. A simple burn-out process subjected to the used membranes in air completely recovered the specific surface area, steady state flux, and oil rejection rate of the virgin membranes. The recycled membranes showed an exceptionally high oil rejection rate (99.9%) with a feed oil concentration of 600 mg/L at an applied pressure of 101 kPa. The typical porosity, pore size, flexural strength, oil rejection rate, and steady state flux of the recycled alumina-coated clay-diatomite composite membrane were 36.5%, 0.12 μm, 32 MPa, 99.9%, and 6.91×10−6 m3 m−2 s−1, respectively, at an applied pressure of 101 kPa.