Investigation of comparative behavior of boron ion rejection from aqueous solution using mixed matrix membranes in nanofiltration process

In this study, flat membranes containing neat polyethersulfone and the mixed matrix membranes containing polyethersulfone and nanoparticles such as titanium dioxide(TiO2) and functionalized multi-walled carbonnanotubes (fMWCNTs) were fabricated by wet phase inversion. And the boron ions' rejection and permeat flux behavior of these prepared membranes were evaluated and compared using the nanofiltration process. The hydrophilic properties of the prepared membranes and their structure were evaluated by measuring the contact angle and the scanning electron microscopy method, respectively. To optimize the amount of boron ion’s rejection percentage and permeate flux on the neat polyethersulfone membrane, the operational parameters such as the weight percentage of polyethersulfone, pH, time, pressure, and boric acid concentration were investigated. Finally, the performance of mixed matrix membranes containing different percentages of nanoparticles was evaluated under these optimal conditions. The results showed that at optimal conditions (pressure=12 bar, polyethersulfone=20% (W/W), concentration of boric acid=20 ppm, time= 30 minutes, and pH=12), all the prepared mixed matrix membranes have higher boron ion rejection percentage and permeate flux than the neat polyethersulfone. The mixed matrix membrane containing fMWCNTs (0.7%wt) has the highest boron ion rejection percentage (95/79%).