Recycling of construction and demolition waste to fabricate cost-effective anorthite ceramic membranes for enhanced separation of an oil-in-water emulsion

Abstract The recycling of construction and demolition waste to prepare cost-effective anorthite membranes was demonstrated by the in-situ synthesis of anorthite. The effects of sintering temperature and calcium loading on the physical properties (porosity, phase composition, microstructure, pore size, nitrogen permeation, and tortuous factor) of the as-synthesized porous membrane were investigated in detail. With the addition of coal cinder and natural bauxite, the anorthite phase was synthesized at 878 °C. Almost all samples had a high porosity of >35% at 900 °C–1000 °C. With the increasing temperature, the porosity of the samples (except for P2 and P4) decreased gradually to close to zero. The variation trend of pore size was consistent with that of the mass fraction of calcium-containing crystals. This occurred because the growth of these crystals as a sintering neck led to the expansion of the pore structure. The increasing temperature caused a decrease of the tortuous factor and an increase of permeance. Due to the presence of anorthite, the as-synthesized membrane became hydroxylated by the alkali-solution treatment and manifested improved hydrophilicity, resulting in an enhanced separation of the oil-in-water emulsion.