Thin film nanocomposite membrane incorporated with polymethyl metharcylate grafted multi-walled carbon nanotubes for gas separation

Abstract

Membrane technology is an appealing alternative to the conventional carbon dioxide (CO2) separation processes due to its design simplicity, energy efficiency and environmentally benign approach. Nanocomposite membrane, especially the thin film nanocomposite (TFN) is a relatively new class of membrane which features good separation performance and practical processing. Yet, the challenge of achieving good dispersion of the nanosized fillers within the polymer matrix remains unsolved. This study investigated on the potential of TFN containing modified multi-walled carbon nanotubes (MWNTs) for gas separation. Mixed acid oxidation, micro-emulsion polymerization and ball milling have been employed to improve the dispersibility of MWNTs. The TFNs were fabricated via interfacial polymerization technique to allow control over the distribution of the fillers. The effects of modification, incorporation scheme and loading of MWNTs on the gas separation performance have been investigated. The results suggested that grafting MWNTs with polymethyl methacrylate (PMMA) allowed good dispersion of the fillers which can be further enhanced by the physical milling to suppress the formation of aggregates. TFN produced by incorporating the milled PMMA-MWNTs (m-PMMA-MWNTs) within the coating layer showed the best separation performance compared to other incorporation scheme. The performance enhancement of the TFN compared to the thin film composite counterpart was endowed by the addition of well-dispersed MWNTs that served as rapid diffusion channels and the formation defect-free skin. The optimum fillers loading is 0.25 g/L which gives TFN with CO2 permeance of 53.5 gas permeation unit (12% increment), CO2/nitrogen selectivity of 61.0 (1% increment) and CO2/methane selectivity of 35.2 (54% increment). TFN embedded with m- PMMA-MWNTs could potentially be used for low pressure carbon capture and storage application with further development