Two hydrophobic porous ethylene-chlorotrifluoroethylene (ECTFE) membranes quenched in water and air were fabricated by thermally induced phase separation and used for water recovery from ammonia-containing humid gas via vapor condensation. The ECTFE membranes were further hydrophobically modified to enhance their condensation performance. The condensate water quality of the modified membrane significantly improved. The mechanisms of the NH3 contamination in the condensate water were discussed. Surface hydrophobic modification slightly increased the flux and recovery stabilities of the membranes. However, the modification also increased the membrane surface roughness, which adversely affects the vapor condensation and droplet evolution on the membrane surface and reduced the recovered water quality. From the material perspective, desirable porous membranes for vapor condensation should have high surface hydrophobicity and smoothness and reasonably large pore sizes. The reasonably large pore sizes would promote noncondensable gaseous contaminants (e.g., ammonia) to go through the membrane, thereby improving the recovered water quality.
Xinran Zhang,Pengfei Ren,Jianhua Zhou,Junyi Li,Zhenxing Li,Ding Wang
This study investigated the formation of disinfection byproducts (DBPs) from a real ammonia-polluted source water treated by a pilot-scale ultraviolet (UV)/chlorine process with subsequent post-chlorination. The experimental results indicated that UV/chlorine treatment enhanced the formation of trihalomethanes (THMs), haloacetic acids (HAAs), and haloacetonitriles (HANs) in post-chlorination, compared to UV or chlorine applied alone under parallel experimental conditions. DBP formation was observed to depend on pH values, chlorine doses, and reaction times. THM formation was higher at pH 9.0 than pH 6.0, while HAAs and HANs were produced more readily at pH 6.0 rather than 9.0. A higher chlorine dose led to a higher amount of DBPs formed after the treatment of UV/chlorine followed by post-chlorination. The concentration of DBPs increased with the UV/chlorine treatment time increasing from 2 to 15 s and then presented a decrease trend with the reaction time prolonging to 30 s. In addition, changes in natural organic matter (NOM) properties were evaluated using three-dimensional fluorescence spectra and parallel factor analysis (PARAFAC) UV/chlorine treatment effectively destroyed humic-like and tyrosine-like components in waters with the maximum fluorescence intensity ( FI m a x ) reduced by 51.4% and 64.6%, respectively, compared to the raw water sample. The decrease of fluorescence of waters exhibited a positive correlation with the formation of DBP-FP in UV/chlorine treatment. Overall, DBP formation from the ammonia-polluted source water caused by UV/chlorine treatment could be managed by carefully determining chlorine doses and contact times to be used in the UV/chlorine process.
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