One-step engineering of low-cost kaolin/fly ash ceramic membranes for efficient separation of oil-water emulsions

Efficient construction of ceramic membranes can decrease the cost and ease the process of wastewater treatment. The total cost of ceramic membranes is mainly determined by the cost of raw materials and energy consumption during sintering process. In this work, fly ash particles recycled from electric plant and kaolin materials were respectively employed as the support and membrane layer of composite ceramic membranes. To match the sintering temperature of the kaolin material and fly ash support, rigid alumina particles were introduced into the supports (AFA supports). Also, the bending strength of the supports was improved when adding alumina particles. The kaolin/fly ash ceramic membrane was obtained by spraying the kaolin dispersion on the AFA supports and co-sintering. The mean pore diameter and water permeance of the membranes were 320 nm and 3650 Lm⁻²h⁻¹ bar⁻¹. When treating oil-water emulsions with oil content of 400 ppm, the oil removal rate was above 98.5% and the stable permeance was close to 530 Lm⁻²h⁻¹ bar⁻¹, likely due to the super-hydrophilic performance of kaolin and the electric repulsion between the membrane and oil droplets. The raw materials cost, sintering energy consumption, and fabrication time were successfully decreased. This work demonstrates the feasibility of low-cost ceramic membranes for efficient wastewater treatment in chemical industries.