Increasing population, rapid urban sprawl, industrialization, and climatic variation are resulting in an increasing fresh water demand. This ever-increasing concern has created a burden on the community and influenced to bargain with the alternate resources. Following this trend, many countries are supplementing their water supply via desalination and water reclamation using reverse osmosis (RO). However, the occurrence of domestically generated micropollutants in the treated effluent subsequent to their inappropriate removal through the membrane have been gaining high attention.
Therefore, membrane fouling consequence to flux decline and permeate quality deterioration has now become the platform for many researchers from the last few decades. To cope these challenges, surface modification is considering as a promising method, however, the permeability of the membrane is being compromised to achieve high removal performance or vice versa. Furthermore, the poor dispersion and disintegration of functionalized group is also challenging in a pressurized system.
Herein, graphene oxide cross-linking polydopamine (GO-PDA) is found encouraging for polyamide RO membrane surface modification to confront with these limitations. In this study, we aimed to obtain ultra-high flux with superior permeate quality from the commercial BW4040AFR (LG Chem’s NanoH2O, Korea) RO membrane (GO-PDA-RO) treating pharmaceuticals and endocrine disruptive compounds (i.e. erythromycin, cefalexin, ofloxacin, hormone, bisphenol A, pentadecafluorooctanoic acid). The morphological detail and uniform coating layer distribution were validated by scanning electron microscopy (SEM) of virgin membrane samples. X-ray photoelectron spectroscopy (XPS) and fourier-transform infrared spectroscopy (FTIR) were also performed to observe chemical composition and percent amount of oxygen-containing functional groups over the coated surface. In addition, the performance of the modified and pristine RO membrane were examined using synthetic feed followed by real seawater as a representative of complex feed solution matrix.
Adding the to transmembrane pressure, permeate flux, and conductivity values, the permeate samples analyzed by liquid chromatography – electrospray ionization – tandem mass spectrometer (HPLC-ESI-MS/MS) showed promising results with high micropollutants rejection (>99%) from the modified membrane. The narrow layer spacing of GO structure and hydrophilic characteristics of PDA worked synergistically to inhibit fouling layer formation by avoiding hydrophobic interaction of the pollutants at the membrane surface. Owing to high surface charge, antimicrobial characteristics, and stable coating layer formation, GO-PDA-RO membrane outperformed for brackish as well as for seawater desalination with less fouling propensity and low operating pressure conditions.