Design of bentonite/polyurethane composite membrane with a high flux in treatment of organic wastewater by using the pigment volume concentration theory

Abstract

The flux and rejection rate of the membrane in wastewater treatment are main factors to evaluate the efficiency of membrane separation. In this study, bentonite was added into polyurethane (PU) as a pigment to prepare a type of composite membrane. The properties of composite membrane were designed and regulated by the pigment volume concentration (PVC) theory to optimize the flux and rejection rate in organic wastewater treatment. FT-IR spectra showed the interaction between bentonite and PU matrix that the swelling degree depended on this synergistic effect. The hydrophilic surface of membrane was contributed by bentonite particles in PU matrix. The PVC of the 3# composite membrane (11.81%) was closest to the critical pigment volume concentration (CPVC). The rejection rate of methylene blue was 97.28%, and at the same time, the water flux was 48.52 L·m−2·h−1. In addition, the rejection rates of typical organic pollutants such as Rhodamine B, phenol and industrial wastewater reached 95.32%, 96.84% and 97.16%, and the fluxes were 36.36 L·m−2·h−1, 41.58 L·m−2·h−1 and 38.84 L·m−2·h−1, respectively. This kind of inorganic-organic composite membrane has the potential to be applied to organic wastewater treatment. This study provides a new method for designing composite membranes by using the PVC theory.