Degradation of Polyamide Nanofiltration Membranes by Bromine: Changes of Physiochemical Properties and Filtration Performance

• Published in: Environmental science & technology 2021-05, Vol.55 (9), p.6329-6339
• Main Authors: Zhao, Huihui, Yang, Linyan, Chen, Xueming, Sheng, Mei, Cao, Guomin, Cai, Lankun, Meng, Shujuan, Tang, Chuyang Y
• Format: Article
• Language: English
• Subjects: Aramid fibers; Bromination; Bromine; Calcium; Chlorine; Coexistence; Degradation; Exposure; Filtration; Hydrophilicity; Hydrophobicity; Incorporation; Membrane permeability; Membranes; Membranes, Artificial; Nanofiltration; Nanotechnology; Nylons; Physicochemical properties; Physiochemistry; Polyamide resins; Polyamides; Sodium chloride; Solutes; Treatment and Resource Recovery; Water Purification; Water treatment
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/acs.est.1c00206

The potential coexistence and interaction of bromine and polyamide membranes during membrane-based water treatment prompts us to investigate the effect of bromine on membrane performance. For fully aromatic polyamide membrane NF90 exposed under a mild bromination condition (10 mg/L), bromine incorporation resulted in more negatively charged (−13 vs −25 mV) and hydrophobic (55.2 vs 58.9°) surfaces and narrower pore channels (0.3 vs 0.29 nm). The permeabilities of water and neutral solutes were reduced by 64 and 69–87%, respectively, which was attributed to the decreased effective pore radius and hydrophilicity. NaCl permeability was reduced by 90% as a synergistic result of enhanced size exclusion and charge repulsion. The further exposure (100 and 500 mg/L bromine) resulted in a more hydrophobic surface (61.7 and 65.5°) and the minor further reduction for water and solute permeabilities (1–9%). Compared with chlorine, the different incorporation efficiency and properties (e.g., atomic size, hydrophilicity) of bromine resulted in opposite trends and/or different degrees for the variation of physicochemical properties and filtration performance of membranes. The bromine incorporation, the shift and disappearance of three characteristic bands, and the increased O/N ratio and calcium content indicated the degradation pathways of N-bromination and bromination-promoted hydrolysis under mild bromination conditions (480 mg/L·h). The further ring-bromination occurred after severe bromine exposure (4800–24,000 mg/L·h). The semi-aromatic polyamide membrane NF270 underwent a similar but less significant deteriorated filtration performance compared with NF90, which requires a different explanation.