Removal of dilute volatile organic compounds in water through graft copolymer membranes consisting of poly(alkylmethacrylate) and poly(dimethylsiloxane) by pervaporation and their membrane morphology

Removal of volatile organic compounds (VOCs) such as benzene and chloroform in aqueous benzene and chloroform solutions through the poly(methylmethacrylate)-poly(dimethylsiloxane) (PMMA-g-PDMS), poly(ethylmethacrylate)-PDMS (PEMA-g-PDMS), and poly(n-butylmethacrylate)-PDMS (PBMA-g-PDMS) graft copolymer membranes was investigated by pervaporation. When aqueous solutions of dilute VOCs were permeated through the PMMA-R-PDMS and PEMA-g-PDMS membranes, these membranes showed a benzene- and chloroform-permselectivity. Permeation and separation characteristics of the PMMA-g-PDMS and PEMA-g-PDMS membranes changed drastically at a DMS content of about 40 and 70 mol%, respectively. Permeation rate and VOC-permselectivity of the PBMA-g-PDMS membrane, however, increased gradually with increasing DMS content, unlike those of the PMMA-g-PDMS and PEMA-g-PDMS membranes. Furthermore, the transmission electron microscope observations revealed that the PMMA-g-PDMS and PEMA-g-PDMS membranes had microphase separations consisting of a PDMS phase and a poly(alkylmethacrylate) phase, but the PBMA-g-PDMS membrane was homogeneous. The permeability and permselectivity for aqueous VOCs solutions through their graft copolymer membranes in pervaporation are discussed in detail from the viewpoint of their membrane structure, and permselectivity was analyzed by the solution-diffusion theory. (C) 2001 Elsevier Science B.V. All rights reserved.