Institute of Nutraceuticals and Functional Foods (INAF) and Dairy Research Center (STELA), Department of Food Sciences and Nutrition, Pavillon Comtois, Université Laval, Sainte-Foy (Qc), Canada G1V 0A6.
J Colloid Interface Sci. 2012 Apr 15;372(1):217-30. doi: 10.1016/j.jcis.2011.12.067. Epub 2012 Jan 18.
The aim of this study was to reveal the mechanisms ruling a fouling growth on both sides of a CMX-SB cation-exchange membrane (CEM), run after run during three consecutive electrodialysis (ED) treatments. A model solution containing a high magnesium/calcium ratio (2/5) was demineralized under two different pulsed electric field (PEF) on-duty ratios and dc current. The results showed a series of mechanisms ruling a multilayer mineral fouling growth and its delay by PEFs. The nature of the fouling layer, during a first run, depended on the diluate pH-value evolutions and the ion migration rates through the membrane. A subsequent multilayer fouling growth during consecutive treatments was ruled by the already formed mineral layers, where gradual sieving effects inverted the migration rates and led to a multistep crystal growth. Calcium carbonate grew on the diluate side of CEM, starting from its amorphous phase to then crystallize in a coexisting presence of aragonite and calcite. Amorphous magnesium hydroxide appeared on CEM apparently through fouling dehydration ruled by the mineral layers themselves and by overlimiting current regimes. A delayed fouling growth was observed for PEF ratio 0.3. A long pause lapse during pulse modes was demonstrated as an important parameter for fouling mitigation.
本研究旨在揭示 CMX-SB 阳离子交换膜（CEM）两侧在连续三次电渗析（ED）处理过程中结垢生长的机制。含有高镁/钙比（2/5）的模型溶液在两种不同的脉冲电场（PEF）占空比和直流电流下进行脱矿处理。结果表明，PEFs 会引发一系列控制多层矿物结垢生长及其延迟的机制。在第一个运行周期中，污垢层的性质取决于稀释液 pH 值的演变和离子通过膜的迁移率。在随后的连续处理中，随后的多层结垢生长受已经形成的矿物质层控制，其中逐渐的筛网效应会反转迁移率并导致多步晶体生长。碳酸钙从无定形相开始在 CEM 的稀释侧生长，然后与文石和方解石共存结晶。无定形氢氧化镁显然是通过污垢自身的脱水和过限电流状态来控制的，出现在 CEM 上。对于 PEF 比为 0.3，观察到结垢生长延迟。在脉冲模式下长时间暂停被证明是减轻结垢的一个重要参数。
