Removal and destruction of endocrine disrupting contaminants by adsorption with molecularly imprinted polymers followed by simultaneous extraction and phototreatment

Molecularly imprinted polymers for environmental adsorption applications

Molecular imprinting polymers (MIPs) are synthetic materials with pores or cavities to specifically retain a molecule of interest or analyte. Their synthesis consists of the generation of three-dimensional polymers with specific shapes, arrangements, orientations, and bonds to selectively retain a particular molecule called target. After target removal from the binding sites, it leaves empty cavities to be re-occupied by the analyte or a highly related compound. MIPs have been used in areas that require high selectivity (e.g., chromatographic methods, sensors, and contaminant removal). However, the most widely used application is their use as a highly selective extraction material because of its low cost, easy preparation, reversible adsorption and desorption, and thermal, mechanical, and chemical stability. Emerging pollutants are traces of substances recently found in wastewater, river waters, and drinking water samples that represent a special concern for human and ecological health. The low concentration in which these pollutants is found in the environment, and the complexity of their chemical structures makes the current wastewater treatment not efficient for complete degradation. Moreover, these substances are not yet regulated or controlled for their discharge into the environment. According to the literature, MIPs, as a highly selective adsorbent material, are a promising approach for the quantification and monitoring of emerging pollutants in complex matrices. Therefore, the main objective of this work was to give an overview of the actual state-of-art of applications of MIPs in the recovery and concentration of emerging pollutants.

Accurate Removal of Toxic Organic Pollutants from Complex Water Matrices

Characteristic emerging pollutants at low concentration have raised much attention for causing a bottleneck in water remediation, especially in complex water matrices where high concentration of interferents coexist. In the future, tailored treatment methods are therefore of increasing significance for accurate removal of target pollutants in different water matrices. This critical review focuses on the overall strategies for accurately removing highly toxic emerging pollutants in the presence of typical interferents. The main difficulties hindering the improvement of selectivity in complex matrices are analyzed, implying that it is difficult to adopt a universal approach for multiple targets and water substrates. Selective methods based on assorted principles are proposed aiming to improve the anti-interference ability. Thus, typical approaches and fundamentals to achieve selectivity are subsequently summarized including their mechanism, superiority and inferior position, application scope, improvement method and the bottlenecks. The results show that different methods may be applicable to certain conditions and target pollutants. To better understand the mechanism of each selective method and further select the appropriate method, advanced methods for qualitative and quantitative characterization of selectivity are presented. The processes of adsorption, interaction, electron transfer, and bond breaking are discussed. Some comparable selective quantitative methods are helpful for promoting the development of related fields. The research framework of selectivity removal and its fundamentals are established. Presently, although continuous advances and remarkable achievements have been attained in the selective removal of characteristic organic pollutants, there are still various substantial challenges and opportunities. It is hopeful to inspire the researches on the new generation of water and wastewater treatment technology, which can selectively and preferentially treat characteristic pollutants, and establish a reliable research framework to lead the direction of environmental science.

Solvent- and Wavelength-Dependent Photolysis of Estrone

The direct photolysis of estrone in solvents ranging from water to cyclohexane is reported. The photodegradation is dominated by lumiestrone, an epimer of estrone resulting from the inversion of the methyl group at carbon 13, regardless of solvent and photolysis wavelength in the range 254-320 nm. Solvent addition products are also observed in lesser amounts. The photodegradation rate in water is an order of magnitude slower than in nonaqueous solvents. Short wavelength excitation enhances photodegradation. Together, these results suggest complicated photophysics underlie the photochemistry with implications for the remediation of environmental estrogens.

Accurate Removal of Trace 17β-Estradiol and Estrogenic Activity in Blended Systems under a Photoelectrocatalytic Circulating Flow

Trace 17β-estradiol (E2) is persistent against advanced treatment when blended with higher concentrations of low-toxicity organics, thus wasting energy. A circulating-flow selective photoelectrocatalysis (CF-SPEC) system is established with a selective E2-TiO₂-NR photoanode, accurately reducing 1 μg L^-1 E2 to less than 0.1 ng L^-1 along with eliminating estrogenic activity even when blended with natural organic matter (NOM) at a thousand times higher concentration. Such high efficiency is derived from the augmented selectivity and activity of E2-TiO₂-NRs toward E2 during CF-SPEC. Under a flow, the difference in adsorption capacity between NOM and E2 is further amplified 5.6-fold. Furthermore, the higher initial ^•OH concentration and faster mass transfer jointly endow CF-SPEC with a stronger oxidation capacity. As a result, the removal of E2 increases by 58.7%, and the elimination of estrogenic activity increases 5.8-fold. In addition, deeper mineralization and less homo- and heterocoupling under CF-SPEC are observed, leading to more thorough estrogenic activity removal. Although additional energy is needed to maintain the flow, there is a 55% decrease in energy consumption due to the accurate removal capacity. This work suggests a combination of flow degradation and surface engineering that can be expanded for the selective removal of toxic trace pollutants in blended systems.

Synthesis, characterization, and evaluation of a selective molecularly imprinted polymer for quantification of the textile dye acid violet 19 in real water samples

A molecularly imprinted polymer (MIP) was developed for the determination of acid violet 19 (AV19) dye. The MIP was synthesized by polymerization using 1-vinyl imidazole (functional monomer) and 2,2'-azobis(2-methylpropionitrile) as the radical initiator. The functional monomer was previously selected by computational simulations. The MIP adsorption data could be fitted using the Langmuir model obtained a Q_m value of 6.93 mg g^-1 and 2.84 mg g^-1 for the corresponding non-imprinted polymer (NIP) and the process followed pseudo-second-order kinetics (k₂ 0.2416 mg g^-1 min^-1 MIP). The BET specific surface areas were 229.6 m² g^-1 and 28.6 m² g^-1, to MIP and NIP, respectively. Analyses showed that the material provided excellent selectivity towards acid violet 19 (AV19) when compared to other analytes including Acid Violet 17 (AV17), Tartrazine (TZ), Acid Red 14 (AR14), Patent blue-VF (PBV), Sunset yellow FCF (SY) and Acid Red 1 (AR1). The calculated K_d value for the MIP was 0.116 L g^-1 and the imprinting factor was 2.89. This alternative and effective material for the enrichment, extraction, and determination of acid violet 19 presents in complex real samples was applied using two different rivers water and industrial effluent, with excellent recoveries values ranging between 85% up to 99%.

Competitive effects of humic acid and wastewater on adsorption of Methylene Blue dye by activated carbon and non-imprinted polymers

Natural organic matter (NOM), present in natural waters and wastewater, decreases adsorption of micropollutants, increasing treatment costs. This research investigated mechanisms of competition for non-imprinted polymers (NIPs) and activated carbon with humic acid and wastewater. Three different types of activated carbons (Norit PAC 200, Darco KB-M, and Darco S-51) were used for comparison with the NIP. The lower surface area and micropore to mesopore ratio of the NIP led to decreased adsorption capacity in comparison to the activated carbons. In addition, experiments were conducted for single-solute adsorption of Methylene Blue (MB) dye, simultaneous adsorption with humic acid and wastewater, and pre-loading with humic acid and wastewater followed by adsorption of MB dye using NIP and Norit PAC 200. Both the NIP and PAC 200 showed significant decreases of 27% for NIP (p=0.087) and 29% for PAC 200 (p=0.096) during simultaneous exposure to humic acid and MB dye. There was no corresponding decrease for NIP or PAC 200 pre-loaded with humic acid and then exposed to MB. In fact, for PAC 200, the adsorption capacity of the activated carbon increased when it was pre-loaded with humic acid by 39% (p=0.0005). For wastewater, the NIP showed no significant increase or decrease in adsorption capacity during either simultaneous exposure or pre-loading. The adsorption capacity of PAC 200 increased by 40% (p=0.001) for simultaneous exposure to wastewater and MB. Pre-loading with wastewater had no effect on MB adsorption by PAC 200.

Removal of endocrine disrupting compounds from wastewater using polymer particles

This study evaluated the use of particles of molecularly imprinted and non-imprinted polymers (MIP and NIP) as a wastewater treatment method for endocrine disrupting compounds (EDCs). MIP and NIP remove EDCs through adsorption and therefore do not result in the formation of partially degraded products. The results show that both MIP and NIP particles are effective for removal of EDCs, and NIP have the advantage of not being as compound-specific as the MIP and hence can remove a diverse range of compounds including 17-β-estradiol (E2), atrazine, bisphenol A, and diethylstilbestrol. Removal of E2 from wastewater was also tested to determine the effectiveness of NIP in the presence of interfering substances and natural organic matter. Removal of E2 from wastewater samples was high and increased with increasing NIP. NIP represent an effective way of removing a wide variety of EDCs from wastewater.

Molecular imprinting science and technology: a survey of the literature for the years 2004-2011

Herein, we present a survey of the literature covering the development of molecular imprinting science and technology over the years 2004-2011. In total, 3779 references to the original papers, reviews, edited volumes and monographs from this period are included, along with recently identified uncited materials from prior to 2004, which were omitted in the first instalment of this series covering the years 1930-2003. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by sections describing fundamental aspects of molecular imprinting including the development of novel polymer formats. Thereafter, literature describing efforts to apply these polymeric materials to a range of application areas is presented. Current trends and areas of rapid development are discussed.

Occurrence of 17α-ethynylestradiol (EE2) in the environment and effect on exposed biota: a review

17α-ethynylestradiol (EE2) is a synthetic hormone, which is a derivative of the natural hormone, estradiol (E2). EE2 is an orally bio-active estrogen, and is one of the most commonly used medications for humans as well as livestock and aquaculture activity. EE2 has become a widespread problem in the environment due to its high resistance to the process of degradation and its tendency to (i) absorb organic matter, (ii) accumulate in sediment and (iii) concentrate in biota. Numerous studies have reported the ability of EE2 to alter sex determination, delay sexual maturity, and decrease the secondary sexual characteristics of exposed organisms even at a low concentration (ng/L) by mimicking its natural analogue, 17β-estradiol (E2). Thus, the aim of this review is to provide an overview of the science regarding EE2, the concentration levels in the environment (water, sediment and biota) and summarize the effects of this compound on exposed biota at various concentrations, stage life, sex, and species. The challenges in respect of EE2 include the extension of the limited database on the EE2 pollution profile in the environment, its fate and transport mechanism, as well as the exposure level of EE2 for better prediction and definition revision of EE2 toxicity end points, notably for the purpose of environmental risk assessment.

Endocrine disruptors compounds, pharmaceuticals and personal care products in urban wastewater: implications for agricultural reuse and their removal by adsorption process

In the last years, a lot of emerging contaminants, such as, endocrine disruptors compounds (EDCs), pharmaceuticals, and personal care products (PPCPs) have been detected in wastewater. Because of their toxicity and possible adverse effects on the environment and humans, their release from urban wastewater treatment plants (UWWTPs) effluents should be minimized, particularly when a wastewater reuse for crops irrigation is expected. Many processes have been investigated for advanced treatment of UWWTP effluents as well as for emerging contaminant degradation; among these, adsorption process was successfully used to remove EDCs and PPCPs from wastewater. This article shortly reviews EDCs and PPCPs removal from UWWTP effluents by adsorption process using conventional and non-conventional adsorbents. The fate of EDCs and PPCPs in UWWTPs and the implications for agricultural wastewater reuse has been addressed too. In spite of the adsorption process looking to be a valuable alternative to other advanced technologies for the removal of emerging contaminants from wastewater, some gaps still remain to evaluate the actual feasibility at full scale. However, according to a few studies available in scientific literature on the use of both powdered activated carbon and granular activated carbon at full scale, adsorption process by activated carbon is a promising, potentially effective, and economically feasible solution for producing safe wastewater for agricultural reuse.

Performance evaluation and application of surface-molecular-imprinted polymer-modified TiO2 nanotubes for the removal of estrogenic chemicals from secondary effluents

The removal of estrogenic chemicals during wastewater reclamation has been a great concern. Current advanced treatment processes are inefficient for the removal of estrogenic chemicals from secondary effluents of municipal wastewater treatment plants (WWTPs) due to the coexistence of other pollutants with less environmental significance which are also removed simultaneously. The search for highly selective and low-cost removal methods is warranted. Therefore, surface-molecular-imprinted polymer-modified TiO(2) nanotube (S-MIP-TiO(2) NT) photocatalysts were fabricated, characterized, and tested for the removal of estrogenic pollutants from wastewater in this study for the first time. Scanning electron microscopy and Fourier-transform infrared spectroscopy studies showed that the TiO(2) NTs (with an average diameter of 60 nm) were successfully imprinted with functional groups (i.e., carboxyl). The adsorption selectivity and photocatalytic activity of the S-MIP-TiO(2) NTs towards template compound (17β-estradiol, E2) were improved, compared with neat TiO(2) NTs. Interestingly, S-MIP-TiO(2) NTs exhibited higher adsorption intensity and photocatalytic selectivity at low concentrations (from 10 ng/L to 100 μg/L, as normal estrogenic chemical concentrations in secondary effluents) of E2 than that at high concentrations (from 10 to 1,000 mg/L). It was also found that some representative estrogenic chemicals and estrogenic activity could be selectively and rapidly removed from secondary effluents of municipal wastewater treatment plants using S-MIP-TiO(2) NTs as photocatalysts. In addition, S-MIP-TiO(2) NT photocatalysts exhibited excellent regeneration characteristics. Photocatalytic treatment using S-MIP-TiO(2) NTs could be a promising approach for the effective removal of estrogenic chemicals from secondary effluents of municipal WWTPs.

Application of molecularly imprinted and non-imprinted polymers for removal of emerging contaminants in water and wastewater treatment: a review

Over the past decade, several studies have reported trace levels of endocrine disrupting compounds, pharmaceuticals, and personal care products in surface waters, drinking water, and wastewater effluents. There has also been an increased concern about the ecological and human health impact of these contaminants, and their removal from water and wastewater has become a priority. Traditional treatment processes are limited in their ability to remove emerging contaminants from water, and there is a need for new technologies that are effective and feasible. This paper presents a review on recent research results on molecularly imprinted (MIP) and non-imprinted (NIP) polymers and evaluates their potential as a treatment method for the removal of emerging contaminants from water and wastewater. It also discusses the relative benefits and limitations of using MIP or NIP for water and wastewater treatment. MIP, and in particular NIP, offer promising applications for wastewater treatment, but their toxicity and possible health effects should be carefully studied before they are considered for drinking water treatment. More research is also required to determine how best to incorporate MIP and NIP in treatment plants.

Processes for the elimination of estrogenic steroid hormones from water: a review

Natural estrogens such as estrone (E1), 17β-estradiol (E2), estriol (E3), and the synthetic one, 17α-ethinylestradiol (EE2), are excreted by humans and animals and enter into environment through discharge of domestic sewage effluents and disposal of animal waste. The occurrence of these substances in aquatic ecosystems may affect the endocrine system of humans and wildlife so it has emerged as a major concern for water quality. Extensive research has being carried out during the last decades on the efficiency of the degradation and/or removal of these hormones in sewage treatment plants (STPs). Conventional and advanced treatments have been investigated by different authors for the elimination of estrogens from water. This paper aims to review the different processes and treatments that have been applied for the elimination of E1, E2, E3 and EE2 from water. With this purpose, physical, biological and advanced oxidation processes (AOP) have been addressed.

Solvent effects on the steady state photophysics of estrone and 17β-estradiol

Absorption and emission yields for estrone and 17β-estradiol were measured in a variety of room temperature solvents. Molar extinction coefficients were found to not vary as a function of solvent, while fluorescence yields were found to be significantly affected by the polarity and hydrogen-bond accepting ability of the solvent, with the yield for 17β-estradiol being highest in nonpolar, hydrogen-bond donating solvents, and lowest in the nonpolar, hydrogen-bond accepting solvent ethyl acetate. Estrone's emission yield was found to be a factor of ten smaller than 17β-estradiol's. Strong solvent and excitation wavelength dependences were found for the relative amounts of emission between estrone's two emission bands, with increased relative emission occurring in nonpolar aprotic solvents, and under higher excitation energies. These results are interpreted with the aid of vertical excitation energies from time-dependent density functional calculations using both explicit and implicit solvation models.

Selective removal of diclofenac from contaminated water using molecularly imprinted polymer microspheres

A molecularly imprinted polymer (MIP) was synthesized by precipitation polymerization using diclofenac (DFC) as a template. Binding characteristics of the MIP were evaluated using equilibrium binding experiments. Compared to the non-imprinted polymer (NIP), the MIP showed an outstanding affinity towards DFC in an aqueous solution with a binding site capacity (Q(max)) of 324.8 mg/g and a dissociation constant (K(d)) of 3.99 mg/L. The feasibility of removing DFC from natural water by the MIP was demonstrated by using river water spiked with DFC. Effects of pH and humic acid on the selectivity and adsorption capacity of MIP were evaluated in detail. MIP had better selectivity and higher adsorption efficiency for DFC as compared to that of powdered activated carbon (PAC). In addition, MIP reusability was demonstrated for at least 12 repeated cycles without significant loss in performance, which is a definite advantage over single-use activated carbon.

Construction of uniformly sized pseudo template imprinted polymers coupled with HPLC-UV for the selective extraction and determination of trace estrogens in chicken tissue samples

To assess the potential risks associated with the environmental exposure of steroid estrogens, a novel highly efficient and selective estrogen enrichment procedure based on the use of molecularly imprinted polymer has been developed and evaluated. Herein, analogue of estrogens, namely 17-ethyl estradiol (EE(2)) was used as the pseudo template, to avoid the leakage of a trace amount of the target analytes. The resulting pseudo molecularly imprinted polymers (PMIPs) showed large sorption capacity, high recognition ability and fast binding kinetics for estrogens. Moreover, using these imprinted particles as dispersive solid-phase extraction (DSPE) materials, the amounts of three estrogens (E(1), E(2) and E(3)) which were detected by HPLC-UV from the chicken tissue samples were 0.28, 0.31 and 0.17 μg g(-1), and the recoveries were 72.5-78.7%, 90.3-95.2% and 80.5-83.6% in spiked chicken tissue samples with RSD <7%, respectively. All these results reveal that EE(2)-PMIPs as DSPE materials coupled with HPLC-UV could be applied to the highly selective separation and sensitive determination of trace estrogens in chicken tissue samples.

Surface molecular imprinting onto fluorescein-coated magnetic nanoparticles via reversible addition fragmentation chain transfer polymerization: a facile three-in-one system for recognition and separation of endocrine disrupting chemicals

In this study, we present a general protocol for the making of surface-imprinted magnetic fluorescence beads via reversible addition-fragmentation chain transfer polymerization. The resulting composites were characterized by X-ray diffraction analysis, transmission electron microscopy, scanning electron microscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, and energy dispersive spectroscopy. The as-synthesized beads exhibited homogeneous polymer films (thickness of about 5.7 nm), spherical shape, high fluorescence intensity and magnetic property (Magnetization (Ms)=3.67 emu g(-1)). The hybrids bind the original template 17β-estradiol with an appreciable selectivity over structurally related compounds. In addition, the resulting hybrids performed without obvious deterioration after five repeated cycles. This study therefore demonstrates the potential of molecularly imprinted polymers for the recognition and separation of endocrine disrupting chemicals.

Performance evaluation and application of molecularly imprinted polymer for separation of carbamazepine in aqueous solution

A molecularly imprinted polymer (MIP) for selective adsorption of carbamazepine (CBZ) in aqueous solution was synthesized by precipitation polymerization using CBZ as a template molecule and methacrylic acid (MAA) as a functional monomer. The performance of the CBZ-MIP was evaluated in terms of selectivity, adsorption capacity, binding characteristics, loading volume, and elution volume. The CBZ-MIP exhibited a high affinity for CBZ over the competitive compound (Diclofenac) and was more suitable to remove low concentrations of CBZ in large-volume water samples. A binding performance experiment indicated that the adsorption of CBZ-MIP was characterized by both specific and non-specific binding interactions. Moreover, the regenerability of the MIP was affirmed in ten sequential cycles of adsorption/desorption without a significant loss in recovery. Finally, the CBZ-MIP was applied to enrich CBZ in environmental water samples, and the CBZ concentrations were subsequently determined using HPLC-UV. The results were in good agreement with corresponding LC-MS/MS data.

A novel separation and enrichment method of 17β-estradiol using aptamer-anchored microbeads

The estrogenic compound 17β-estradiol (E2) is widely studied for its potential endocrine disruption effects. Due to the low level of E2 present in the environment, it is highly desirable to develop a sensitive and efficient separation and enrichment method for E2 analysis. In this paper, we proposed a novel E2 preconcentration method using anti-E2 aptamer-anchored isothiocyanate-modified beads (NCS beads). The glass beads are chemically modified with primary amino group, and then treated with phenylene diisothiocyanate (PDITC) to generate an isothiocyanate group, which is reactive towards the amine group. The amino-modified anti-E2 aptamer can be easily covalently immobilized onto the as-prepared NCS beads. The experimental results demonstrated that the aptamer affinity microbeads could selectively retain and separate E2 compound. The effects of the operation parameters on retention of E2, including washing condition, eluting condition, the number of beads, and the incubation time were investigated. Moreover, high-performance liquid chromatography with preconcentration of E2 on the aptamer affinity microbeads was applied to detect the E2 in the spiked water samples and obtained a good recovery.