Ultra-low temperature co-sintering of water glass (WG)-bonded silicon carbide ceramic membranes for oil-water separation

Abstract

Silicon carbide (SiC) ceramic membranes with high water permeance and good antifouling properties are promising for efficient oil-water separation. However, the high production cost of SiC membranes, in particular contributed by their high sintering temperatures, restricts the commercialization and full-scale applications of the membranes. In this work, a new coupling method of low-temperature co-sintering and spraying was proposed to prepare asymmetric water glass (WG)-bonded SiC microfiltration membranes for oil-water separation and reduce the cost of production. For this purpose, alkaline WG was used as the sintering aid to lower the sintering temperature to 600 °C and as the pH regulator to optimize the dispersion of the SiC powder. A facile optimization of the ultra-low temperature co-sintering program facilitated the formation of a crack-free multilayer of the membranes, by preventing thermal stress imbalance between the membrane layer and the support layer. The mean pore size of the co-sintered ceramic membrane was 0.25 μm, corresponding to high pure water permeance of above 2400 L· m−2·h−1·bar−1. In comparison with other reported ceramic membranes, the as-prepared co-sintered membranes exhibited higher stable-permeance (234.8 ± 9.4 L·m−2·h−1·bar−1) and a higher oil rejection (98.9 ± 0.2%) even under a lower transmembrane pressure (0.2 bar), which were attributed to the superhydrophilicity and underwater superoleophobicity of the membranes, during filtration with oil-in-water emulsions (500 mg· L−1). The low-temperature co-sintering method, aided by WG-based bonding, provides technical support for designing high performance ceramic membranes at reduced cost of production, which may promote their practical applications in wastewater treatment.