The University of British Columbia, Department of Civil Engineering, 2002 - 6250 Applied Science Lane, Vancouver, B.C, Canada.
Water Res. 2013 Sep 15;47(14):5392-9. doi: 10.1016/j.watres.2013.06.018. Epub 2013 Jun 28.
Sodium hypochlorite is commonly used as a cleaning agent to remove adsorbed foulants from PVDF based micro/ultra filtration membranes in water and wastewater treatment applications. Although effective for fouling control, extended sodium hypochlorite exposure can affect the physical/chemical characteristics and hinder the treatment performance of these membranes. To assess these effects, PVDF based membranes were exposed to sodium hypochlorite at different concentrations for varying periods of time, and the physical/chemical characteristics of the virgin and sodium hypochlorite exposed membranes were compared. The membranes were characterized based on chemical composition (FTIR and NMR), mechanical strength (yield strength), surface hydrophilicity (contact angle), pore size and porosity (scanning electron microscopy and challenge test), and membrane resistance (clean water permeation test). The results indicated that exposure dose and concentration of the sodium hypochlorite used have significant influence on the membrane characteristics. The impact of sodium hypochlorite exposure on the parameters investigated could be most accurately and consistently correlated to an exposure dose relationship of the form C(n)t (where, C = concentration and t = exposure time) rather than the Ct relationship commonly used to define the extent of exposure to cleaning agents. For all the parameters investigated, the power coefficient n was less than 1 indicating that time had a greater impact on the changes than did the concentration of the sodium hypochlorite. The results suggest that the use of sodium hypochlorite for chemical cleaning, at concentrations that are higher than those typically used for chemical cleaning would have less of an effect on the characteristics of the membrane materials. Changes in the characteristics were attributed to the oxidation of the hydrophilic additives (HA) present in blended PVDF membranes.
次氯酸钠通常用作清洁剂，用于去除水和废水处理应用中基于聚偏氟乙烯（PVDF）的微/超滤膜上吸附的污染物。尽管对于控制污染非常有效，但长时间暴露于次氯酸钠会影响这些膜的物理/化学特性并阻碍其处理性能。为了评估这些影响，将基于 PVDF 的膜暴露于不同浓度的次氯酸钠中不同的时间段，并比较了原始膜和暴露于次氯酸钠的膜的物理/化学特性。基于化学成分（傅里叶变换红外光谱和核磁共振）、机械强度（屈服强度）、表面亲水性（接触角）、孔径和孔隙率（扫描电子显微镜和挑战测试）以及膜阻力（清水渗透测试）对膜进行了表征。结果表明，暴露剂量和次氯酸钠浓度对膜特性有显著影响。次氯酸钠暴露对所研究参数的影响可以最准确和一致地与暴露剂量关系 C(n)t（其中，C 表示浓度，t 表示暴露时间）相关联，而不是与通常用于定义清洁剂量的 Ct 关系相关联。对于所有研究的参数，幂系数 n 小于 1，表明时间对变化的影响大于次氯酸钠浓度的影响。结果表明，在高于通常用于化学清洁的浓度下使用次氯酸钠进行化学清洁对膜材料特性的影响较小。特性的变化归因于存在于共混 PVDF 膜中的亲水性添加剂（HA）的氧化。
