Development of Thin-Film Composite Membranes for Nanofiltration at Extreme pH

Abstract

Water recycling is one of the most sustainable solutions to growing water scarcity challenges. However, wastewaters usually contain organic pollutants and often are at extreme pH, which complicates the treatment of these streams with conventional membranes. In this work, we report the synthesis of a robust membrane material that can withstand prolonged exposure to extreme pH (of 1 or 13 for 2 months). Polyamine thin film composite (TFC) membranes are prepared in situ by interfacial polymerization between 1,3,5-tris(bromomethyl)benzene (tBrMeB) and p-phenylenediamine (PPD). Contrary to conventional polyamide TFC membranes, enhanced pH stability is achieved by eliminating the carbonyl groups from the polymer network. The membranes showed pure water permeance and molecular weight cutoff (MWCO) of 0.28 ± 0.09 L m −2 h −2 bar −1 and 820 ± 132 g mol −1 , respectively. The membrane performance is further enhanced by manipulating the monomer structures and replacing p-phenylenediamine with mphenylenediamine, resulting in a higher permeance of 1.3 ± 0.3 L m −2 h −1 bar −1 and a lower MWCO of 566 ± 43 g mol −1 . Given the ease of fabrication and excellent stability, this chemistry represents a step forward in the fabrication of robust membranes for industrial wastewater recycling.

Cyclomatrix polyphosphazene organic solvent nanofiltration membranes

“…As expected, the pore diameter distribution based on model 2, ranging from 0 to 5 nm, is wider than that obtained from model 1 (0-2 nm). In addition, the obtained pore size distribution based on model 1 is in line with the reported value for the other types of NF/OSN membranes, where model 1 was used to calculate pore size distribution as well [51,67].…”

“…In addition, the PEG-based MWCO data can be used to determine the pore diameter of the selective layer [51,52]. PEG molecules can form spheres of a certain radius in the solution, and their molecular weight, M w (g mol − 1 ), can be related to the PEG radius and diameter, r (Å) and d (Å), via the Stokes-Einstein equation [53]:…”

Covalent organic polymers for aqueous and organic solvent nanofiltration

“…On the other hand, after acidic treatment, the permeance further drops to 10.9 Lm − 2 h − 1 bar − 1 , which could be explained by extra crosslinking in the COP structure caused by HNO 3 doping. This phenomenon have been previously reported where a polyprotic acid forms hydrogen bonds with the N atoms present in the polymer backbone, reducing its pore size [47]. This could also explain the sharp increase in salt retention, as the membrane becomes tighter and more positively charged.…”

Cellulose Acetate Membranes: Fouling Types and Antifouling Strategies—A Brief Review

“…Commercial RO membranes were initially obtained from PA and CA membranes. Additionally, TFC membranes are used for nanofiltration (NF) processes due to their thin selective layer and high mechanical strength, resulting in high flux [20]. Compared to CA membranes, TFCs show better salt rejection, higher water flux, and higher resistance to biological attacks, in addition to working at a broader range of temperatures and pH.…”