Constructed "sandwich" structure to obtain recyclability and high rejection rate high-flux CA@HMSN@h-BN/PDA membrane for efficient treatment of dye wastewater

It is necessary to develop a nanofiltration membrane that can remove dye molecules efficiently and is not easily polluted for the treatment of textile industry wastewater. A novel high-flux CA@HMSN@h-BN/PDA membrane with a "sandwich" structure was obtained by assembling the support layer of the Hollow mesoporous silica nanoparticles (HMSN), and the isolation layer of the h-BN/PDA on the Cellulose acetate (CA) membrane. HMSN was synthesized using ZIF-8 as a self-sacrificial template to provide improved permeability. h-BN/PDA obtained by modifying hexagonal boron nitride (h-BN) with polydopamine (PDA) brought higher hydrophilicity, rejection rate, and stability to the membrane. The study solved the problem that the membrane separation process requires sacrificing flux and recyclability for high rejection rates. CA@HMSN@h-BN/PDA membrane has a super-hydrophilic property (water contact angle of 22.5°) and high pure water flux (4419.4 L·m−2·h−1·bar−1). Meanwhile, the CA@HMSN@h-BN/PDA membrane achieves a high rejection rate (over 99.5%) due to the special "sandwich" structure. Through cycling experiments, CA@HMSN@h-BN/PDA membranes exhibit recyclability. More importantly, CA@HMSN@h-BN/PDA membranes maintain stable performance in complex environments, such as extremely acidic/alkaline or inorganic salt interference environments. Thus the CA@HMSN@h-BN/PDA membrane has the potential for future wastewater treatment.