The effect of Merpol surfactant on the morphology and performance of PES/PVP membranes: antibiotic separation

International Journal of Industrial Chemistry https://doi.org/10.1007/s40090-019-0192-5 RESEARCH The effect of Merpol surfactant on the morphology and performance of PES/PVP membranes: antibiotic separation Maryam Omidvar1 · Zahra Hejri1 · Ahmad Moarefian2 Received: 12 March 2018 / Accepted: 15 July 2019 © The Author(s) 2019 Abstract The present study used modified nanofiltration (NF) membranes to remove the emerging contaminant of amoxicillin (AMX) from synthetic wastewater. For this purpose, Merpol surfactant and polyvinylpyrrolidone were added to the casting solutions to prepare flat sheet asymmetric polyethersulfone (PES) NF membranes through phase inversion process. Then, the effect of adding Merpol surfactant at different concentrations on the morphology, hydrophilicity, and pure water flux (PWF) of the membranes, as well as the separation of AMX from aqueous solutions was investigated. The characteristics of the prepared membranes were studied by scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), contact angle (CA) measurement and performance tests. The obtained results approved the improved hydrophilicity of the PES membranes after adding Merpol surfactant to the casting solution. The findings also revealed a gradual increase in the average size of the membrane pores in sub-layer and thinner top layer, proportional to the increase of surfactant content in the solution. The results also confirmed the increase of PWF under the influence of surfactant increase. As a result, for the membrane containing 8 wt% Merpol additive, the lowest CA (52.08°), the highest PWF (76.31 L/m2 h), and maximum AMX excretion (97%) were achieved. Keywords Antibiotic · Hydrophilicity · Merpol · Nanofiltration · Polyethersulfone membrane Introduction Membrane separation technology has been widely applied in various industries because of its advantages, such as low energy consumption, no phase transition, and easy to scale up [1, 2]. This technology is a promising solution for removal of the emerging contaminants [3]. Nanofiltration (NF) membranes have a selectivity capability in the region between reverse osmosis (RO) and ultrafiltration (UF), which make it possible to separate monovalent * Maryam Omidvar Zahra Hejri Ahmad Moarefian 1 Chemical Engineering Department, Islamic Azad University, Quchan Branch, Quchan, Iran 2 Chemical Engineering Department, Faculty of Petroleum, Gas and Petrochemical Engineering, Persian Gulf University, Bushehr 7516913798, Iran and divalent salts, as well as organic solutes with molecular weights up to 1000 g/mol [4]. The use of this relatively new technology has grown steadily in recent years [5, 6]. This is mainly due to low energy consumption and the high efficiency of this separation technology, which has led to its widespread use in various industries, such as water softening, drinking-water purification, dye and antibiotic purification, salt removal, and waste treatment [7]. Nanofiltration is also increasingly used in new water treatment programs. In addition, to have highly biologically stable water, NF membranes offer a very good removal of the organic micropollutants. The reason is that the molecular weight cut-off (MWCO) values of NF membranes are often in the same range as that of endocrine-disrupting compounds (EDCs), pharmaceutically active compounds (PhACs) and personal care products (PPCPs) [8, 9]. Polymeric membranes, which occupy the vast majority of the market for water treatment, suffer significantly from fouling [10]. Fouling on the membrane surfaces has been regarded as the most serious problem on membrane filtration technologies [11]. 13 Vol.:(0123456789) International Journal of Industrial Chemistry Polyethersulfone (PES), due to its high chemical, thermal, and mechanical stability, has widely been used to synthesis membranes for a variety of applications [12]. The main limiting factor for using this chemical compound is its low hydrophilicity, which increases membrane fouling [13, 14]. One way to modify the performance of PES nanofiltration membranes is to increase their hydrophilicity. So far, the impact of the increased hydrophilicity of the membrane surfaces and pore walls on the reduction or suppression of membrane fouling has been confirmed by many scholars around the world in recent years [15]. Adding hydrophilic polymer additives, such as polymeric surfactants, to PES membranes is a widely accepted way to improve hydrophilicity of the membranes. Surfactants are surface-active agents, constituting the most important category of detergents [16]. For this purpose, various surfactants have yet been introduced, including but not limited to, Pluronic F127 [17], Tween 80 [18], Tween 20 [15], Tetronic 1307 [12], Triton X100, CTAB and SDS [19], Brij S100 [20] and Brij58 [21, 22]. Antibiotics have become emerging contaminants of aquatic ecosystems in recent years. These pollutants, even in small quantities, are dangerous due to their high persistence in aquatic ecosystems. Studies have revealed the inefficiencies of conventional wastewater treatment methods in eliminating this pollutant, as evidence of presenting antibiotic contaminants in natural environments have been reported from almost every corner of the world [23, 24]. The presence of such compounds in natural environments has raised concerns about their toxicity to humans and animals, as well as the emergence of bacteria and genes resistant to antibiotics [25, 26]. Nowadays, membrane filtration based on NF and RO membranes can be considered one of the most promising techniques known to remove antibiotic compounds [27]. There are numerous studies that have confirmed the effectiveness of this approach in eliminating antibiotic compounds, such as amoxicillin (AMX). As such, Zazouli et al. [28] used two commercial NF membranes, namely SR2 and SR3, to compare their performance in rejection of AMX. According to their findings, the SR3 NF membranes had a better performance than SR2 in the removal of AMX. They reported a removal rate of 95% for SR3 NF membranes and 64.9% for SR2 NF membranes. In another study by Shahtalebi et al. [29], the performance of commercial NF4040 membrane in AMX removal was estimated to be 97%. Their results showed that the AMX content of the feed stream is an influential factor in the rejection of AMX antibiotics so that the removal efficiency will be lower at higher concentrations. There is no previously published article regarding the effects of the addition of Merpol surfactant as hydrophilic additive on the fundamental characteristics of the PES 13 nanofiltration membranes to remove antibiotics, such as AMX. Thus, in this study, the effect of adding this surfactant into the PES casting solution on the morphology, hydrophilicity, and pure water flux (PWF) of the membranes as well as the rejection of AMX was investigated in detail. Chemicals and methods Chemicals In this study, PES was bought from BAS (...truncated)