Hydrophobic Membrane for Water Recovery from Humid Gas by Membrane Condenser: Effects of Membrane Properties on Recovered Water Quality

Two hydrophobic porous ethylene-chlorotrifluoroethylene (ECTFE) membranes quenched in water and air were fabricated by thermally induced phase separation and used for water recovery from ammonia-containing humid gas via vapor condensation. The ECTFE membranes were further hydrophobically modified to enhance their condensation performance. The condensate water quality of the modified membrane significantly improved. The mechanisms of the NH3 contamination in the condensate water were discussed. Surface hydrophobic modification slightly increased the flux and recovery stabilities of the membranes. However, the modification also increased the membrane surface roughness, which adversely affects the vapor condensation and droplet evolution on the membrane surface and reduced the recovered water quality. From the material perspective, desirable porous membranes for vapor condensation should have high surface hydrophobicity and smoothness and reasonably large pore sizes. The reasonably large pore sizes would promote noncondensable gaseous contaminants (e.g., ammonia) to go through the membrane, thereby improving the recovered water quality.