Abstract Membranes have emerged as promising technologies for treatment of non-traditional waters, but fouling and poor rejection of small, neutral solutes (e.g., boric acid) impede their further implementation for water purification. Boron rejection is increased by raising the pH to convert boric acid to borate ion, but this change often leads to calcite supersaturation. This study investigated the use of a hybrid electrodialysis-nanofiltration/reverse osmosis (ED-NF/RO) system to reduce fouling from calcite precipitation and calcium-polysaccharide sorption to NF/RO membranes. Also, the study examined the potential of the hybrid process to increase permeate flux and boron rejection during NF/RO of synthetic saline water. ED pretreatment reduced calcite oversaturation and reduced flux decline during NF/RO. Low alginate concentrations (25 mg/L) limited NF/RO fouling, but high concentrations (100 mg/L) appeared to promote calcite scaling. ED pretreatment reduced the osmotic pressure of the NF/RO feed water, enabling lower operating pressures or greater permeate water fluxes. Boron rejection during NF/RO increased with ED pretreatment, probably due to stronger electrostatic repulsion and an increase in the fraction of total boron present as B(OH)4− following ED. This hybrid ED-NF/RO system shows promise as a novel approach to enhancing the performance of current membrane systems for treating complex feed waters.

中文翻译：

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电渗析预处理在纳滤/反渗透脱盐过程中提高硼去除率和减少结垢的应用

摘要 膜已成为处理非传统水的有前途的技术，但结垢和对小的中性溶质（例如硼酸）的排斥性差阻碍了它们在水净化中的进一步应用。通过提高 pH 值以将硼酸转化为硼酸根离子，硼的去除率会增加，但这种变化通常会导致方解石过饱和。本研究调查了使用混合电渗析-纳滤/反渗透 (ED-NF/RO) 系统来减少方解石沉淀和钙-多糖吸附到 NF/RO 膜的污垢。此外，该研究还检查了混合工艺在合成盐水的 NF/RO 过程中增加渗透通量和硼截留率的潜力。ED 预处理减少了方解石过饱和并减少了 NF/RO 期间的通量下降。低海藻酸盐浓度 (25 mg/L) 限制了 NF/RO 结垢，但高浓度 (100 mg/L) 似乎会促进方解石结垢。ED 预处理降低了 NF/RO 给水的渗透压，从而实现更低的操作压力或更大的渗透水通量。NF/RO 期间的硼排斥随 ED 预处理而增加，这可能是由于更强的静电排斥和 ED 后以 B(OH)4- 形式存在的总硼的比例增加。这种混合 ED-NF/RO 系统有望作为一种新方法来提高当前膜系统处理复杂进水的性能。NF/RO 期间的硼排斥随 ED 预处理而增加，这可能是由于更强的静电排斥和 ED 后以 B(OH)4- 形式存在的总硼的比例增加。这种混合 ED-NF/RO 系统有望作为一种新方法来提高当前膜系统处理复杂进水的性能。NF/RO 期间的硼排斥随 ED 预处理而增加，这可能是由于更强的静电排斥和 ED 后以 B(OH)4- 形式存在的总硼的比例增加。这种混合 ED-NF/RO 系统有望作为一种新方法来提高当前膜系统处理复杂进水的性能。