Development of Polydopamine Forward Osmosis Membranes with Low Reverse Salt Flux

Abstract

Application of forward osmosis (FO) is limited due to membrane fouling and, most importantly, high reverse salt fluxes that deteriorate the concentrated product. Polydopamine (PDA) is a widely used, easily applicable, hydrophilic, adhesive antifouling coating. Among the coating parameters, surprisingly, the effect of PDA coating temperature on the membrane properties has not been well studied. Polyethersulfone (PES) 30 kDa ultrafiltration membranes were PDA-coated with varying dopamine concentrations (0.5–3 g/L) and coating temperatures (4–55 °C). The quality of the applied coating has been determined by surface properties, water permeability and reverse salt flux using a 1.2 M MgSO4 draw solution. The coating thickness increased both with the dopamine concentration and coating temperature, the latter having a remarkably stronger effect resulting in a higher PDA deposition speed and smaller PDA aggregates. In dead-end stirred cell, the membranes coated at 55 °C with 2.0 g/L dopamine showed NaCl and MgSO4 retentions of 41% and 93%, respectively. In crossflow FO, a low reverse MgSO4 flux (0.34 g/m2·h) was found making a very low specific reverse salt flux (Js/Jw) of 0.08 g/L, which outperformed the commercial CTA FO membranes, showing the strong benefit of high temperature PDA-coated PES membranes to assure high quality products.

Adhesion Optimization between Incompatible Polymers through Interfacial Engineering

“…A comparison of the AFM 2D height and phase images of the PI film before and after PDA coating (Figure 5b,d) clearly shows a more marked aggregate morphology on the PI-coated surface, which is the first information about the morphology of the PDA coating. The PDA aggregates varied in size (mainly in the nanometer range) and homogeneously covered the surface of the PI, confirming previous studies [37]. The particulate shapes at the sub-micron scale are observed in Figure 4c, and it was assumed that these objects were large PDA aggregates.…”

Impact of MWCO and Dopamine/Polyethyleneimine Concentrations on Surface Properties and Filtration Performance of Modified Membranes

“…The PDA exhibits chemical stability, from the interactions of the catechol group, and hydrophilic characteristics, due to the presence of the amino group [ 27 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ]. As a result of the hydrophilic character and affinity with several polymers, DA is a strategy highly used in MSM to create anti-fouling characteristics; reducing the interaction of the membrane surface with various solutes, including proteins, which are usually hydrophobic, improving filtration performance, and reducing cleaning cycles [ 30 , 37 , 38 , 43 , 47 , 48 , 49 , 50 , 51 ]. As an improvement of the method, Yang et al (2014) [ 52 ] proposed a single-step deposition of DA with a hydrophilic polymer, polyethyleneimine (PEI).…”

Tailoring the Surface Chemistry of Anion Exchange Membranes with Zwitterions: Toward Antifouling RED Membranes

“…Permselectivity data for AEMs modified with PDA are scarce in literature; nevertheless, Vaselbehagh et al reported a decreased OCV, 58 which is directly related to permselectivity, for AEMs modified with PDA, but in that case the modification time was much longer than in the present study (24 h vs 1 h) and the deposition temperature (30 °C versus room temperature) was higher, with both time and temperature strongly enhancing layer formation and thus decreasing the overall membrane properties. 59 Figure 4 shows the membrane electrical resistance measured at the different stages in the surface modification process.…”