Fabrication of low thermal conductivity yttrium silicate ceramic flat membrane for membrane distillation

This paper reports on the successful fabrication of gamma-Y2Si2O7 membranes with low thermal conductivity, which is an important membrane property for achieving high performance in membrane distillation process. Single-phase gamma-Y2Si2O7 powder was first synthesized by calcination of SiO2 and Y2O3 powders, with 3 wt% LiYO2 as a sintering aid. The membrane was produced by tape-casting of a suspension of this powder. After sintering at 1300 degrees C for 4 h, a flat membrane was obtained, which had a thickness of 0.5 mm, 49% porosity, 0.9 mu m pore diameter, and low thermal conductivity of 0.497 W/m.K at 32 degrees C, and 0.528 W/m.K at 100 degrees C. The obtained membrane presented hydrophobic features (water contact angle was 132 degrees) after surface modification, which resulted in formation of a strongly adhered robust hydrophobic SiNCO nanoparticle layer on its surface. The resultant hydrophobic membrane was tested in water desalination experiments using a sweeping gas membrane distillation (SGMD) device. High water flux of 10.07 L.m(-2).h(-1) was achieved for a 20 wt% NaCl feeding solution and a temperature at the feed of 90 degrees C. Stable water flux and rejection rates were recorded in long-term experiments ( > 400 h).