The Effects of Salt Type and Salt Concentration on the Performance of Magnetically Activated Nanofiltration Membranes

The effects of salt ion type and salt concentration on flux and rejection improvement of magnetically activated micromixer nanofiltration membranes were investigated. Polymers with varying chain length and chain density were grafted on the NF270 membranes using the well-controlled atom transfer radical polymerization reaction. Superparamagnetic nanoparticles that respond to an oscillating magnetic field were conjugated at the polymer chain ends. The effects of micromixing on breaking the concentration polarization boundary layer were investigated by determining the percentage improvement in flux and rejection in the presence of an external oscillating field. Systematic trends on the salt ion size and feed concentration as well as grafting degrees were observed. The magnetically activated micromixers are more effective in breaking down severer concentration polarization when the charge and concentration of the salt ions are higher. In addition, higher density and longer polymer chains induce stronger micromixing effects.