Quantification of solute–solute interactions in steroidal hormone removal by ultrafiltration membranes

Abstract

Micropollutant removal by membrane filtration is variable and can be influenced by the presence of organic matter. When considering removal mechanisms, many studies have focused on membrane adsorption and solute-foulant interactions; however, little is known regarding the influence of solute-solute interactions as these are typically difficult to quantify. In this study experimental organic matter-water partition coefficients (K OM ) were applied to quantify and elucidate the influence of solute-solute interactions for steroidal hormone removal by ultrafiltration. The results indicated that the removal of all hormones increased in the presence of organic matter and this was related to hormone -organic matter interactions. Organic matter did not increase membrane adsorption or cause significant fouling for most molecular weight cut-off (MWCO) membranes, thus solute-solute interactions were the dominant mechanism for hormone removal as expected from previous quantification of such interactions using a specifically developed solid-phase microextraction (SPME) technique. While quantification was only partially successful at low organic carbon concentrations, clear evidence of the importance of solute-solute interactions was demonstrated in concentration studies. Experimental removal and estimated removal due to solutesolute interactions for estrone was comparable at high organic matter concentrations of 25-50 mgC/L for both 10 (48-52%) and 100 kDa (33-38%) membranes, suggesting that organic matter concentration was an important factor in solute-solute interactions. This study represents the first time that experimental organic matter-water partition coefficients have been applied to assess solute-solute interactions in membrane filtration, specifically ultrafiltration.Keywords: Ultrafiltration, organic matter, steroidal hormone, solute-solute interaction, partition coefficient 2 Introduction The detection of micropollutants, such as pharmaceuticals, pesticides and steroidal hormones, in effluent from conventional wastewater treatment plants has generated worldwide interest over the last few decades [1,2]. This is of concern as many of these micropollutants are considered endocrine disrupting chemicals and can have implications for the growth and development of organisms. For example, the presence of steroidal hormones, such as estradiol and estrone, can cause reproductive disruption in fish at sub nanogram per litre (ng/L) concentrations [3]. Consequently, there is a need for improved micropollutant removal during water and wastewater treatment and this has led to increasing interest in advanced water treatment processes, such as membrane filtration. The removal of micropollutants by membranes is variable and the presence of organic matter, which is ubiquitous in surface and wastewaters, can affect removal [4][5][6]. To better understand the influence of organic matter on micropollutant removal by membrane filtration three mechanisms of interaction interplay, namely membrane adsorption, solute-foulant intera...

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Retention of pesticide Endosulfan by nanofiltration: Influence of organic matter–pesticide complexation and solute–membrane interactions

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