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

This paper reports on the successful fabrication of γ-Y 2 Si 2 O 7 membranes with low thermal conductivity , which is an important membrane property for achieving high performance in membrane distillation process. Single-phase γ-Y 2 Si 2 O 7 powder was first synthesized by calcination of SiO 2 and Y 2 O 3 powders, with 3 wt% LiYO 2 as a sintering aid. The membrane was produced by tape-casting of a suspension of this powder. After sintering at 1300 °C for 4 h, a flat membrane was obtained, which had a thickness of 0.5 mm, 49% porosity, 0.9 μm pore diameter, and low thermal conductivity of 0.497 W/m⋅K at 32 °C, and 0.528 W/m⋅K at 100 °C. The obtained membrane presented hydrophobic features (water contact angle was 132°) 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 °C. Stable water flux and rejection rates were recorded in long-term experiments (>400 h).