Surface Modification of Ultrafiltration Membranes with 1,4-Benzoquinone and Polyetheramines to Improve Fouling Resistance.

Membrane fouling remains a key challenge for membrane separations. Hydrophilic membrane surface modification can mitigate irreversible foulant deposition, thereby improving fouling resistance. We report new hydrophilic membrane coatings based on 1,4-benzoquinone and various commercially available polyetheramines. These coatings, prepared from 1,4-benzoquinone and Jeffamine EDR 148, poly(benzoquinone-Jeffamine EDR 148) (p(BQ-EDR 148)), were used to modify polysulfone (PS) ultrafiltration membranes. In fouling experiments using an oil/water emulsion, membranes exhibited comparable fouling resistance to that of polydopamine (pDA)-modified membranes. Based on contact angle measurements, p(BQ-EDR 148) and pDA-modified membranes have similar levels of hydrophilicity, and both exhibited higher threshold flux values than those of their unmodified analogues. Based on their similar threshold flux values, p(BQ-EDR 148)-modified (76 LMH) and pDA-modified membranes (74 LMH) should have similar fouling resistance. Moreover, the mean pore size of p(BQ-EDR 148)-modified membranes can be tuned, while keeping the pure water permeance constant, by changing the deposition time and molar ratio of benzoquinone to EDR 148 in the modification solution.

The effects of salt concentration and foulant surface charge on hydrocarbon fouling of a poly(vinylidene fluoride) microfiltration membrane.

The effects of inorganic salts and organic hydrocarbons on membrane fouling are often investigated independently. However, in many cases, these foulants are commonly found together, and such mixtures are rarely the subject of fouling studies. In this study, crude oil-in-water emulsions were formulated at three different added NaCl concentrations, 0, 10-3 and 10-1 M. Surface properties, such as surface tension and surface charge, of these emulsions and a poly(vinylidene fluoride) (PVDF) microfiltration (MF) membrane were characterized. The Derjaguin-Landau-Verwey-Overbeek (DLVO) model was utilized to simulate membrane-oil droplet and oil layer-oil droplet surface interactions. The DLVO model qualitatively predicted increasing fouling propensity with increasing emulsion salt concentration. The PVDF MF membrane was challenged with crude oil-in-water emulsions in constant permeate flux crossflow fouling tests to characterize the fouling propensity of the various emulsions, and the results were consistent with the model predictions.