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

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.

A novel WARS mutation (p.Asp314Gly) identified in a Chinese distal hereditary motor neuropathy family.

Distal hereditary motor neuropathy (dHMN) is a clinically and genetically heterogeneous group of inherited neuropathies characterized by distal limb muscle wasting and weakness with no or minimal sensory abnormalities. To investigate the clinical and genetic features of dHMN caused by WARS mutations in mainland China, we performed Sanger sequencing of the coding and untranslated region (UTR) regions of WARS in 160 unresolved dHMN and Charcot-Marie-Tooth (CMT) index patients. We detected a novel heterozygous variant c.941A>G (p.Asp314Gly) of WARS in an index patient from an autosomal dominant dHMN family including five affected members over three generations. The variant completely co-segregates with the dHMN phenotype in the family, and it was classified as likely pathogenic according to the American College of Medical Genetics and Genomics standards and guidelines. The clinical features included juvenile to adult onset (15-23 years), distal wasting and weakness, minimal sensory disturbance and length-dependent motor axonal degeneration with CMT examination score ranging from 6 to 10. Our report further confirms the role of WARS in dHMN and indicates that the variant c.941A>G (p.Asp314Gly) of WARS is related to a mild to moderate affected and later onset phenotype of dHMN.