Lin Dachao, Bai Langming, Xu Daliang, Zhang Han, Guo Tiecheng, Li Guibai, Liang Heng
State Key Laboratory of Urban Water Resource and Environment (SKLUWRE), School of Environment, Harbin Institute of Technology, Harbin, 150090, P.R. China.
Water Res. 2021 May 1;195:116989. doi: 10.1016/j.watres.2021.116989. Epub 2021 Feb 28.
The aim of this study was to evaluate the effects of oxidation on humic-acid-enhanced gypsum scaling in different nanofiltration phases, including the short-term membrane flux behaviors and the long-term ones. On the basic of correlation analysis between the changing physicochemical properties of feed solution and membrane fouling, the inner mechanisms were revealed from aspects of bulk crystallization (interaction between humic acid and inorganic ions) and surface crystallization (compositions and morphologies of surface crystallization). Furthermore, the reliability of applicating differential log-transformed absorbance spectroscopy for predicting membrane fouling was also systematically evaluated. There was an upward trend in short-term membrane fouling with increasing dosage of NaClO, while long-term membrane fouling decreased after an initial increase. During short-term filtration, the enhanced combination between inorganic ions and the humic acid with stronger density of carboxyl groups, which was generated more easily under stronger oxidation conditions, favored the earlier appearance of flux decline. During long-term filtration, the size of bulk crystallization depended on the total content of carboxyl groups in feed solution. Both of them increased firstly and then decreased with increasing oxidation. The terminal fouling layer resistance also shared a similar tendency with them, because the deposition of bulk crystallization on membranes and the formation of dense scaling layer were the direct reasons for the long-term membrane fouling. Furthermore, the differential log-transformed absorbance spectroscopy was proven to be an efficient approach to predict short-term membrane fouling, especially in the wavelength range of 260 to 280 nm. This research could not only provide guidance on alleviating oxidation-enhanced membrane fouling in nanofiltration but also propose an efficient way to predict the membrane fouling which was influenced by the interaction between organic matters and inorganic ions.
本研究的目的是评估氧化对不同纳滤阶段腐殖酸增强石膏结垢的影响，包括短期膜通量行为和长期膜通量行为。基于进料溶液理化性质变化与膜污染之间的相关性分析，从体相结晶（腐殖酸与无机离子之间的相互作用）和表面结晶（表面结晶的组成和形态）方面揭示了内在机制。此外，还系统评估了应用差分对数变换吸光光谱法预测膜污染的可靠性。随着次氯酸钠剂量的增加，短期膜污染呈上升趋势，而长期膜污染在最初增加后下降。在短期过滤过程中，无机离子与羧基密度更高的腐殖酸之间的增强结合，在更强的氧化条件下更容易产生，有利于通量下降的更早出现。在长期过滤过程中，体相结晶的大小取决于进料溶液中羧基的总含量。随着氧化程度的增加，两者均先增加后减少。最终的污垢层阻力也呈现出类似的趋势，因为体相结晶在膜上的沉积和致密结垢层的形成是长期膜污染的直接原因。此外，差分对数变换吸光光谱法被证明是预测短期膜污染的有效方法，尤其是在260至280nm的波长范围内。本研究不仅可以为减轻纳滤中氧化增强的膜污染提供指导，还可以提出一种预测受有机物和无机离子相互作用影响的膜污染的有效方法。
