Constructing polyamide/ceramic composite membranes for highly efficient and selective separation of dyes and salts from solution†

Abstract

Membrane separation technology has been recognized as an effective approach to remove dyes from dyeing wastewater that are crucial for improving the quality of the pigmentation effect in the printing and dyeing industry. However, the trade-off between membrane permeability and selectivity is an inherent drawback of molecular separation membranes, which hampers the development of large-scale applications of the membrane separation process. In this work, we provide a facile approach to construct a highly selective polyamide (PA) layer on a ceramic membrane through the interfacial polymerization of branched polyethylenimine (PEI) and trimesoyl chloride (TMC) for the selective separation of dyes and salts from wastewater. With high positive surface zeta-potential (100 mV) and excellent hydrophilicity, the PA/ceramic composite membranes exhibit ultra-high solution permeance (496.4 L m⁻² h⁻¹ bar⁻¹) while treating simulated dye/salt aqueous solutions containing 40 ppm Congo red (CR) and 1 g L⁻¹ NaCl, which is 30 times higher compared with commercial polyamide nanofiltration membranes. Interestingly, the separation factor of NaCl to CR of the PA/ceramic composite membranes reaches above 980, which is far superior to the state-of-the-art nanofiltration membranes reported recently. Moreover, PA/ceramic membranes possess a relatively ideal long-term stability, with their permeance remaining at 280 L m⁻² h⁻¹ bar⁻¹ after 10 h of testing. Taken together, the PA/ceramic composite membranes are highly promising for dye desalination and purification.