Development of carbon dot-modified polyethersulfone membranes for enhancement of nanofiltration, permeation and antifouling performance

A novel mixed matrix nanofiltration membrane was developed by blending carbon dots (CDs) into a polyethersulfone (PES) matrix. The resulted membranes were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflection (ATR), zeta potential, tensile strength, overall porosity, and water contact angle tests. Pure water flux, antifouling, as well as salt and dye rejection properties were also studied. Fouling resistance of the prepared nanocomposite membranes was tested with filtration of a bovine serum albumin (BSA) solution. The calculated roughness parameters showed that addition of CDs can effectively reduce the roughness value of the PES membrane. The membrane permeability raised to the maximum value of 76.5 kg/m(2) h, which is almost twice the bare PES, by step-wise increasing of the CDs dosage from 0.05 to 0.50 wt%. The 0.50 wt% PES/CDs membrane also showed significant antifouling properties, with the total and irreversible fouling values of 35.6 and 20.3%, respectively, compared to the values of 54.7 and 46.3%, in case of the bare PES. Salt rejection was remarkably improved after addition of CDs with the sequence of Na2SO4 > MgSO4 > NaCl, after 90 min of filtration. The dye rejection was near total removal with above 97% in all prepared membranes, where the maximum dye removal efficiency (98.9%) was observed for the 0.50 wt% PES/CDs, introducing CDs as an excellent membrane modifier for wastewater treatment applications.