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.
Highlights
Forward osmosis (FO) is an emerging membrane process that uses only the osmotic pressure difference between two solutions as the driving force for water transport
There is an increase in the number of studies related to FO that investigate and improve the process conditions as well as FO membrane properties to enhance the efficiency of the process [3]
Industrial application of FO is still limited due to poor performance of the existing membranes that suffer from high reverse salt flux (Js ) and low water flux (Jw ), internal concentration polarization (ICP) and fouling [3,4,5,6]
Summary
Forward osmosis (FO) is an emerging membrane process that uses only the osmotic pressure difference between two solutions as the driving force for water transport. Energy efficient regeneration of the draw solution is an important bottleneck still [7] and has brought up the research on hybrid systems with FO such as FO-membrane distillation [8], FO-reverse osmosis (RO) [9], and FO-nanofiltration (NF) [10]. The latter hybrid system shows promising results that can recover draw solutions energy efficiently using draw solutes based on divalent ions such as Na2 SO4 or MgSO4 due to the higher rejection rates [11,12], allowing the use of NF instead of tight RO membranes [13,14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
