Multifunctional stable PDA/RGO/MOFs&SiO2-COOH membrane with excellent flux and anti-fouling performance for the separation of organic dye and oil/water

Abstract

• A novel nano-sized bimetallic MIL53(Fe-Co) was synthesized by low-cost hydrothermal method . • Low agglomerated bimetallic MOF modified by carboxylated silica successfully formed a stable membrane with graphene oxide . • Ultrafast MIL-S/RGO/PDA membrane possessed a flux of 1905.11 L·m −2 ·h −1 ·bar −1 for pure water and excellent rejection and anti-fouling performance for dye wastewater and oil in emulsions. In this work, bimetallic MIL53(Fe-Co) nanorod was modified by SiO 2 -COOH nanoparticles to obtain a novel MOF with low aggregation, and then intercalated into the reduced graphene oxide (RGO) layer crosslinked by polydopamine (PDA) to form a super-hydrophilic membrane with selective adsorption. The composite material was characterized by various analytical techniques. Owing to the low agglomeration of bimetallic MIL53(Fe-Co) and improved layer spacing of RGO , the stable composite membrane exhibited a water contact angle of approximate 0°, with the dye solution flux of 1721.46 L·m −2 ·h −1 ·bar −1 for methylene blue (MB) and 1834.88 L·m −2 ·h −1 ·bar −1 for malachite green (MG), the dye solution flux was increased by 31 and 33 times compared with M0, respectively. Meanwhile, the rejection rates of MB and MG were 99.46% and 99.4% with an excellent tolerance to a wide range of pH. Furthermore, the composite membrane shows a huge adsorption capacity in treating dye solution with high concentration and large volume for reusability due to the improvement of hydrophilicity. It also performed excellently in the field of separating oil/water emulsion with the flux of 539.79 L·m −2 ·h −1 ·bar −1 and rejection of 98.12%. In conclusion, the composite membrane with extraordinary hydrophilicity, strong adsorption capacity, and superior anti-fouling performance with low costs endows possibility of massive manufacture in commercial production for wastewater separation and purifications.