Removal of insoluble barium scales from reverse osmosis membranes by grafting molecular springs

Reverse osmosis (RO) membranes have been widely used in water treatment systems and exhibit outstanding separation performance. However, due to the complex composition of industrial wastewater, insoluble inorganic scales (e.g., barium sulfate) are difficult to remove from the membrane surface, which severely impairs the membrane performance. Herein, pH-responsive “molecular springs” were grafted onto the fouled polyamide RO membrane by directly penetrating the inorganic scale layers. The “molecular springs” stretch and shrink with pH variations, enabling the removal of barium sulfate scales through simple alkali-acid cleaning. The content of barium scales on the membrane surface was found to significantly decrease from 45.74 % to 0.61 %, resulting in an increase of membrane flux from 60.99 L/(m 2  h) to 71.94 L/(m 2 h). For the full size membrane modules, this study has also demonstrated that the insoluble scales on the industrial RO membrane can be removed as effectively and easily as the soluble scales by grafting “molecular springs”.