Preparation and characterization of aliphatic cyclopolymer derived membranes for water treatment

Official URL: https://risc01.sabanciuniv.edu/record=b3146362_(Table of contents)

The need for clean water is increasing all over the world due to the growth of the population, agricultural activities, and industrial applications. Reverse osmosis (RO) water treatment membrane technology is an emerging technology as it is the most cost-effective way to reach clean water (Yang et al., 2019). Cellulose acetate (CA) and polyamide thin film composite (PA-TFC) membranes are the most common, commercially available RO membranes. CA is an ideal bio-based membrane material with its excellent film-forming ability, cost-effectiveness, biodegradability, and renewability. Compared to aromatic PA-TFC membranes, the main advantages of CA-based RO membranes are ease of manufacture and chlorine resistance. However, flux, fouling resistance, and mechanical strength need to be improved in CA membranes. On the other hand, PA-TFC membranes have excellent separation performance, yet they need improvements in chlorine and fouling resistance. At this point, the development of innovative membrane materials and technologies to obtain potable water is critically important. In this study, tert-butyl alpha-(hydroxymethyl) acrylate (TBHMA) ether dimer cyclopolymer and its carboxylic acid v functional derivative were synthesized, and for the first time, used as membrane materials for water treatment applications. Cyclopolymer membranes were produced in two different ways. Firstly, CA/tert-butyl cyclopolymer (TBCP) composite membranes were produced by the non-solvent induced phase separation (NIPS) process. For this purpose, TBCP polymers with different molecular weights were synthesized. The effects of TBCP content relative to CA, the molecular weight of TBCP, and the viscosity of the casting solution on the performance of produced membranes were investigated. Secondly, acid cyclopolymer thin film composite (CP-TFC) membranes were produced. CP-TFC membranes were prepared by solution coating of acid cyclopolymers on a polysulfone support layer. Carboxylic acid functional cyclopolymers (ACP) were obtained by the acid hydrolysis of tert-butyl ester groups of TBCP and used as membrane materials. The membranes were fabricated from ACPs based on the metal ion crosslinking properties of carboxylic acid groups. Characterization of synthesized cyclopolymers was performed using nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). For the analysis of surface properties and morphology of produced membranes, scanning electron microscope (SEM), water contact angle (WCA), and energy dispersive x-ray spectroscopy (EDS) were used. Flux and salt rejection analyses of produced membranes by both approaches were performed at both RO and nanofiltration levels in a high-pressure membrane filtration system. Performance analyses showed that the novel CA/TBCP composite membranes present better flux performance compared to CA membranes and can be used as RO and nanofiltration membranes. On the other hand, it was demonstrated that the iron (Fe) ion cross-linked membrane can be used for nanofiltration applications in ionically cross-linked carboxylic acid cyclopolymer TFC membranes.