Designing Multifunctional Coatings for Cost-Effectively Sustainable Water Remediation

Multifunctional coatings derived from bioinspired dopamine (DA) have attracted a lot of attention for water environmental remediation recently. Nevertheless, the high cost of DA monomers seriously hampers their broad application. Herein, an elegant multifunctional coating, which could be deployed as a selective adsorbent or loose nanofiltration membrane for removing of dyes and antibiotics from water, was designed based on the Michael-addition and Schiff-base reactions between cost-effective plant-derived gallic acid (GA) and branched polyethylenimine (PEI) at room temperature. Aside from the extremely low cost of GA (about 5% of that of DA), the resultant GA/PEI coatings possessed much better performance than DA/PEI coatings. When deployed as a dye adsorbent, the bioinspired GA/PEI coatings exhibited much higher selectivity, showing 40% increase in anionic dye adsorptive capability and 30% decline in cationic dye adsorptive capability compared with DA/PEI coatings. When applied as a nanofiltration membrane to separate antibiotic solutions, the multifunctional coatings demonstrated solution flux as high as 41.3 L m–2 h–1 at 5 bar alongside 96.2% azithromycin (AH) rejection, showing a 20% increase in flux and 10% increase in rejection compared with DA/PEI nanofiltration membranes. Therefore, our cost-effective multifunctional GA/PEI coatings show promise for use in sustainable water remediation applications.