Beneficial utilization of Al/Si/O-rich solid wastes for environment-oriented ceramic membranes

Wide application of traditional multilayer ceramic membrane has been severely restricted by high costs associated with rare membrane materials and high sintering temperature. In this study, typical solid wastes (coal fly ash, river sediment and sewage sludge) were adopted as raw materials to provide an Al-Si-O matrix for single-layer ceramic membranes. Phase identification shows anorthite as major crystalline phase, while bulk density and pore characteristics of the membranes varied with different raw material compositions, with flexural strengths of 40.82-71.46 MPa, and average pore size of 0.23 μm, 0.28 μm, 0.32 μm and 0.84 μm. When the membranes were applied in an oily water treatment, the oil rejection reached >98 % when using any of the four membranes with oil/water emulsion permeate flux remaining at ∼1200 L/m²·h. Furthermore, the stability of ceramic membranes in harsh environmental conditions was confirmed, with negligible weight loss ratios after being corroded in acidic/alkalic media. In addition, more than 95 % of original flux can be achieved even after six cycles, which confirmed the excellent recyclability of the membranes. The successful fabrication and application of the environment-oriented single layer ceramic membranes from the Al-Si-O solid waste matrix provided a promising "waste-to-resource" strategy for beneficial utilization of typical solid wastes as ceramic raw materials.