Effective biofouling control of reverse osmosis membranes via plant extract coatings

Abstract

Biofouling, as a main challenge in reverse osmosis (RO) membranes, has been attempted to be mitigated via surface modification of membranes via synthetic chemicals. However, the use of plant-based materials as an alternative green approach has gained specific attention due to its environmentally benign and cost-effective nature. Herein, a green method is introduced to sustainably engineer RO membrane surfaces by utilizing the leaf-extract powders of Lawsonia inermis and Isatis tinctoria for reducing their biofouling propensity and improve cleaning effectiveness. This surface modification significantly enhanced the hydrophilicity of the membrane surface while retaining high salt-rejection performance and water flux. Furthermore, in the biofouling analyses of membranes against bacterial solutions, the Lawsonia inermis-coated membrane showed the lowest flux decline and the highest flux recovery rate. As hypothesized, this can be attributed to the improved hydrophilicity and the experimentally proven antibacterial activity of the biomass. This study illustrates plant-extract-based surface modification as an economical, environmentally friendly, and promising method for enhancing the antifouling properties of RO membranes, even under relatively higher operating pressures.