Indigenous and low-cost fly-ash based tubular ceramic membranes for sustainable oil-water emulsion treatment and water reuse applications

The presence of oil in water can have a devastating impact on the environment, harming wildlife, ecosystems, and water quality. The oil content in industrial wastewater typically varies from 100 to 1000 mg/L, necessitating a reduction to 5 mg/L before discharge. To address the treatment of these oil-water emulsions, tubular membranes were produced using a horizontal extrusion method. The membranes comprised fly ash, quartz, calcium carbonate, and α-alumina in a weight ratio of 70%, 20%, 5%, and 5%, respectively. A solution of 2 wt.% carboxymethylcellulose (CMC) sodium salt in water is used as a binder for the ceramic precursors. The sintered membranes at 1100°C (FA_1100) and 1200°C (FA_1200) were found to have average pore diameters of 0.15 and 0.11 μm, porosity of 37.31 and 36.67%, and mechanical stability of 31.65 and 38.53 MPa, respectively. The pure water permeability of FA_1100 and FA_1200 was estimated to be 9.89 × 10−8 and 3.79 × 10−8 m3 /m2.kPa.s, respectively. The separation efficiency of these membranes was evaluated through cross-flow filtration at five different pressure levels, ranging from 69 kPa to 345 kPa for an oil-water emulsion of concentration 100 mg/L. The oil removal efficiency of the membranes increased progressively with increasing pressure, and complete oil removal was observed at a pressure of 345 kPa. The membrane FA_1100 showed the best permeate flux and rejection combination. The permeate produced from these ceramic membranes is fully reusable in the oil industry, which can contribute to addressing the current water scarcity issue.Research highlights A cost-effective tubular ceramic membrane for treating oil-water emulsions has been developed domestically.Increasing the sintering temperature reduces the porosity and pore size of the prepared membrane.Membranes displayed superior compressive strength compared to other clay-based membranes.Complete removal of oil was achieved using the membrane under crossflow mode.