Fundamental thermodynamic mechanisms of membrane fouling caused by transparent exopolymer particles (TEP) in water treatment
Fundamental thermodynamic mechanisms of membrane fouling caused by transparent exopolymer particles (TEP) in water treatment
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DOI：
10.1016/j.scitotenv.2022.153252
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发表时间：
2022-01-25
影响因子：
9.8
通讯作者：
Zhang, Meijia
中科院分区：
文献类型：
--
作者：
Pan, Zhenxiang;Zeng, Bizhen;Zhang, Meijia
虽然透明的外聚合物颗粒（TEP）具有很高的结垢潜力，但其潜在的结垢机制尚未得到很好的揭示。在目前的工作中，污染的TEP在不同的Ca 2+浓度（0至1.5 mM）下的特性进行了研究。TEP定量和过滤试验表明，TEP含量随Ca 2+浓度的增加而增加，而TEP的比过滤阻力（SFR）受Ca 2+浓度的影响呈单峰型。当SA浓度为0.3g·L ~（-1）时，TEP的SFR在Ca ~（2+）浓度为1 mM时达到峰值。一系列表征表明，TEP颗粒的微观结构转变是TEP溶液电阻变化的主要原因。光学显微镜观察表明，在临界Ca 2+浓度（本研究中SA浓度为0.3 g·L-1时为1 mM）以上和以下，形成的TEP分别以c-TEP（平均粒径为0.24 μ m）和p-TEP（平均粒径为1.05 μ m）的形式存在。热力学分析表明，c-TEP的粘附能力（-249，989和-303，692 kT）是p-TEP（-12，905 kT）的19倍多，这会加速污垢层的形成。此外，在临界值以下，钙离子浓度对SFR的影响可以用Flory-Huggins晶格理论和分子间的优先配位来解释。在临界值以上，降低的SFR可以归因于由p-TEP形成的“大尺寸裂纹结构”饼层。本研究揭示了TEP引起膜污染的基本机理，加深了对TEP污染的认识，有助于开发有效的污染控制策略。
While transparent exopolymer particles (TEP) has high fouling potential, its underlying fouling mechanisms have not yet been well revealed. In current work, fouling characteristics of TEP under different Ca2+ concentrations (0 to 1.5 mM) were investigated. TEP quantification and filtration tests showed that TEP contents increased with Ca2+ concentration, while TEP's specific filtration resistance (SFR) under the influence of Ca2+ concentration presented a unimodal pattern. The peak of TEP's SFR reached at Ca2+ concentration of 1 mM when SA concentration was 0.3 g.L-1. A series of characterizations suggested that microstructure transformation of TEP particles was the main contributor to the resistance variations of TEP solution. The optical microscope observation showed that above and below the critical Ca2+ concentration (1 mM when SA concentration is 0.3 g.L-1 in this study), the formed TEP existed in the form of c-TEP (average particle size is 0.24 mu m) and p-TEP (average particle size is 1.05 mu m), respectively. Thermodynamic analysis showed that the adhesion ability of c-TEP (-249,989 and - 303,692 kT) was more than 19 times than that of p-TEP (-12,905 kT), which would accelerate foulant layer formation. In addition, below the critical value, the increased SFR with Ca2+ concentration could be explained by integrating Flory-Huggins lattice theory with the preferential intermolecular coordination. Above the critical value, the decreased SFR can be attributed to the formation of a "large-size crack structure" cake layer from the p-TEP. This study revealed fundamental mechanisms of membrane fouling caused by TEP, greatly deepening understanding of TEP fouling, and facilitating to development of effective fouling control strategies.