Graphene quantum dots modified polyvinylidenefluride (PVDF) nanofibrous membranes with enhanced performance for air Gap membrane distillation

This study investigates the potential of novel graphene quantum dots (GQDs)/polyvinylidene fluoride (PVDF) nanofibrous membranes for water desalination via air gap membrane distillation (AGMD) process. Different contents of GQDs were loaded in/on nanofibrous membrane for obtaining the desired structure for AGMD process. The resultant GQDs/PVDF nanofibrous presented a slight decrease in water contact angle and considerable increase in liquid entry pressure of water (LEPw). The sample containing 0.25 wt.% GQDs exhibited porosity of > 90%, LEPw of > 135 kPa, mean average surface roughness of 189.24 nor and water contact angle of > 125 degrees. Furthermore, the BET analysis exhibited that the mean pore diameter and effective surface area of nanofibrous membrane were modified at presence of GQD. AGMD experiments indicated that the higher water flux of 17.6 kg/m(2) h and salt rejection of about 99.7% were achieved for GQD3P membrane containing 0.25 wt% GQDs compared to neat PVDF nanofibrous membrane with water flux of about 14.7 kg/m(2) h and salt rejection of about 94.5% (partial wetting occurred after 4 h) during filtration of 3.5 wt.% NaCl solution for 8 h under feed and permeate temperatures of 60 degrees C and 20 degrees C, respectively. Eventually, GQD3P exhibited the water flux of 10.8 kg/m(2)h and reliable salt rejection of > 99.5% over 60 h experiment.