Superior Reverse Osmotic Membranes From Etching PA(ZIF)-TFN Membranes With Xylenol Orange Disodium Salt

Polyamide (PA) based thin-film nanocomposite (TFN) membranes containing zeolitic imidazolate framework (ZIF) particles, denoted as PA (ZIF)-TFN membranes, were fabricated via interfacial polymerization (IP) between m-phenylenediamine (MPD) and 1,3,5-benzenetricarbonyl chloride (TMC). ZIF-8 particles were incorporated by direct dispersion into the oil-phase solution. Subsequently, the membranes were etched with xylenol orange disodium salt (XO) under acidic conditions to produce reverse osmosis (RO) membranes with improved water flux and salt rejection. These improvements were attributed to additional water-permeation channels and the sealing of non-selective interface defects. Solution pH, etching duration, and XO concentration also play roles in the structure and performance of the optimized RO membranes. After 12 h of etching, superior TFN/XO (12) RO membranes were obtained with rejection rate increased from (99.0% ± 0.2%) to (99.7% ± 0.1%), and water flux increased from (42.3 ± 0.9 L·m −2 ·h −1 ) to (65.1 ± 0.9 L·m −2 ·h −1 ). In addition, the membranes exhibited excellent boron removal rate, operational stability, and anti-pollution performance under conditions of 32,000 ppm NaCl and 55 bar.