Microwave-assisted Technique Research Articles

Green synthesis and optimization of zinc oxide quantum dots using the Box–Behnken design, with anticancer activity against the MCF-7 cell line

A green strategy and cost-effective approach was adapted to prepare Zinc oxide quantum dots (ZnO QDs) for biomedical applications. The prepared ZnO QDs may hold great promise as sensing scanners for diagnostics and therapy, as demonstrated in our current study. Zinc sulfate, Azadirachta indica, Aloe vera gel and Catharanthus roseus leaves extract were used to synthesize a novel natural Zinc oxide bionanocomposite (ZnO BC) and used as a precursor to prepare ZnO QDs by microwave-assisted technique. The ZnO BC was characterized by SEM–EDX, FT-IR, XRD, Zeta potential, and particle size analysis. The optical properties of QDs were investigated using UV and PL spectrophotometers. Experimental factors like the concentrations of ZnO Nps, C. roseus, and Aloe vera were evaluated using Box–Behnken design (BBD). MTT and hemolysis assay was performed using ZnO BC and ZnO QDs. Maximum absorbance was observed at optimized values of 0.5% ZnO Nps, 1 g A. vera gel, and 0.5 ml C. roseus leaf extract of ZnO QDs against BBD. There was a decreased viability rate, ranging from 60 to 15% for 0.5 mg/ml ZnO BC and 45 to 5% for 5 mg/ml ZnO QDs which revealed a tenfold decrease in cell viability with less concentration scale for 5 mg/ml of ZnO QDs when compared with that of 0.5 mg/ml ZnO BC. Also, the hemolysis test shows that the hemolysis ratio was below 0.5%, indicating non-hemolysis of ZnO QDs. Cellular morphology by results was supported by phase-contrast microscopy images. Good biocompatibility and high anticancer activity were noticed for ZnO QDs when compared to ZnO BC and provide versatile applications in the field of nano-biomedicine.Graphical abstract

Understanding the Working Mechanism of the Novel HKUST-1@BPS Composite Materials as Stationary Phases for Liquid Chromatography.

Composite materials have been used based on coordination polymers or microporous metal-organic frameworks (MOFs) combined with mesoporous matrices for adsorption-related techniques, which enable outflanking some adverse phenomena manifested during pristine components operation and enhance the performance and selectivity of the resulting materials. In this work, for the first time, the novel HKUST-1@BPS composites synthesized by the microwave-assisted (MW) technique starting from microporous HKUST-1 (Cu3(btc)2) MOF and biporous silica matrix (BPS) with bimodal mesopore size distribution were comparatively studied as materials for liquid-phase adsorption techniques utilizing the high-performance liquid chromatography (HPLC) method and benzene as a model adsorbate. It was established that the studied HKUST-1@BPS composites can function as stationary phases for HPLC, unlike the pristine HKUST-1 and bare BPS materials, due to the synergetic effect of both components based on the preliminary enhanced adsorbate mass transfer throughout the silica mesopores and, subsequently, its penetrating into HKUST-1 micropores. The suggested mechanism involves the initial deactivation of open metal Cu2+ sites in the HKUST-1 framework structure by isopropanol molecules upon adding this polar component into the mobile phase in the region of the isopropanol concentration of 0.0 to 0.2 vol.%. Thereafter, at the medium range of varying the isopropanol concentration in the eluent of 0.2 to 0.3 vol.%, there is an expansion of the previously inaccessible adsorption centers in the HKUST-1@BPS composites. Subsequently, while further increasing the isopropanol volume fraction in the eluent in the region of 0.3 to 5.0 vol.%, the observed behavior of the studied chromatographic systems is similar to the quasi-normal-phase HPLC pattern. According to the obtained thermodynamic data, benzene adsorption into HKUST-1 micropores from solutions with a vol.% of isopropanol in the range of 0.4 to 5.0 follows the unique entropy-driven mechanism previously described for the MIL-53(Al) framework. It was found that HKUST-1 loading in the composites and their preparation conditions have pronounced effects on their physicochemical properties and adsorption performance, including the adsorption mechanism.

Structural, optical and electrical properties of Cu2ZnSnS4 thin film deposited by electron beam evaporation method

In this research work, the Cu2ZnSnS4 (CZTS) powder was synthesized using microwave-assisted technique. Sandwich device of Al/ CZTS /Al thin film was deposited by electron beam gun evaporation method (EBG). The optical and structural properties of CZTS have been investigated using UV–visible optical absorption, scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The XRD pattern confirmed the formation of kesterite structure for CZTS. SEM micrograph revealed the crystalline and porous surface characteristic of CZTS thin film. The CZTS particles have band gap energy 1.6 eV that was determined by UV–visible. In order to specify the dominant conduction mechanism, AC conductivity of CZTS thin film was measured at different temperatures and frequencies (290 K<T < 410 K and 102 Hz <f< 105 Hz). At the temperature range from 290 K to 410 K for 104 Hz <f< 105 Hz, hopping is the dominant conduction. The exponent s values (from 0.67 to 0.86) confirm the hopping mechanism in accordance with Jonscher law, also.

Microwave irradiation assisted intensive and quick delignification of lignocellulosic biomass, and confirmation by spectral, morphological and crystallinity characterization

The purpose of this work was to use a microwave-assisted technique to improve and accelerate lignin removal from rice straw biomass. Using a Box-Behnken experimental design, the effect of four critical process parameters, viz. microwave power (480–800 W), irradiation time (4–12 min), bleaching solution concentration (0.4–3.0 %), and bleaching time (1–5 h) on the delignification (%) was investigated, and the process was optimised using response surface methodology. The experimental data best fitted a quadratic model with an R2 of 0.9964. The optimized value of process parameters (in aforementioned sequence) was found to be 671 W, 8.66 min, 2.67 %, and 1 h respectively, for the best delignification of 93.51 percent.The absence of lignin peaks (1516 and 1739 cm−1) was corroborated by deconstructed morphological structure and higher crystallinity in the optimised delignified sample (53.7 %).

Stability mechanisms for microwave-produced solid lipid nanoparticles

Tween® 20 stabilised stearic acid solid lipid nanoparticles (SLNs) were prepared using a one-pot microwave-assisted microemulsion technique. Two model water-insoluble drugs, the carboxylic acid-based indomethacin, and the imidazole-based miconazole nitrate, were then used to load the SLNs, and their subsequent physical properties (particle size and zeta potential) were measured and used to predict dispersion stability.Drug-free SLNs had a particle size of 239 nm and a zeta potential of − 29 mV. Indomethacin-loaded SLNs had a particle size of 266 nm and zeta potential of − 30 mV. Miconazole-loaded SLNs had a particle size of 266 nm and zeta potential of + 15 mV. These values were found to be relatively stable (under mildly acidic conditions) and recommend the suitability of the SLNs as a drug carrier.In all cases, the particle size and zeta potential were shown to be pH-dependent. For particle size, a minimum value was obtained at approximately pH 5, which corresponds to the pKa of the lipid used (stearic acid) indicating stearic acid adsorption onto the surface is likely to be at least partly responsible for dispersion stability. We conclude that dispersion stability arises from a combination of electrostatic stability (from adsorbed stearic acid) and limited steric stability from non-ionic (Tween® 20) surface-associated micelles.Dispersions were found to be unstable under alkaline conditions despite the increasingly negative zeta potential of all dispersions. This was observed as an increasingly larger particle size at pH > 7 combined with the observation that particle sizes at pH > 7 were also unstable and continued to increase with time. Visual observations showed dispersions physically broke within a few days at pH values > 7.The encapsulation efficiency (EE) and loading capacity (LC) of drug-loaded SLNs were shown to be close to their theoretical maximum (100%) at low pH, but decreased to < 20%, in the case of indomethacin-loaded SLNs, at a pH >> 7. Interestingly, the EE and LC of miconazole-loaded SLNs when first formed were relatively unaffected by pH. pH control, therefore, is very important to particle stability, and the pH should be kept neutral to mildly acidic.

Performance of green and conventional techniques for the optimal extraction of bioactive compounds in bee pollen

SummaryThe exploitation of phenolic compounds in different fields has motivated researchers to explore eco‐friendly and efficient extraction techniques. This study aimed to comparatively reveal that green extraction techniques (microwave‐ and ultrasound‐assisted) are alternative to conventional extraction (maceration and magnetic stirring) with positive impact on the phenolic content, antioxidant activity, and bioactive profile of bee pollen extracts. The highest total phenolic and flavonoid content was reached using the microwave‐assisted technique (MAE) with equivalent values of 28 and 8 mg g−1, with magnetic stirring and maceration showing a lower value. The composition profile of the extracts revealed the presence of twenty‐six bioactive compounds, including thirteen phenolics and thirteen phenylamides. Although the extraction technique had little impact on the chemical diversity, the amount of bioactive compounds raised significantly with the use of the green extraction techniques, with gains between 40% and 60% for phenolics and up to 200% for phenylamides. The radical scavenging activity and the reducing power of the extracts confirmed that bee pollens are potent antioxidant source, with the most bioactive extracts corresponding to green extraction techniques. Consequently, all findings recommend the use of MAE as the technique most effective for the extraction of bioactive compounds from naturally encapsulated structures such as bee pollen.

Modifying HKUST-1 Crystals for Selective Ethane Adsorption Using Ionic Liquids as Synthesis Media

Novel adsorbents for methane and ethane based on HKUST-1 metal-organic framework were synthesized by microwave (MW) assisted technique using ionic liquids (ILs) as synthesis media. It was found that the MW synthesis time remarkably impacts both the product yield and the physico-chemical characteristics of the produced HKUST-1 material. The crystalline phase purity, crystallite size/dispersion and textural properties of the synthesized HKUST-1 matrices determine their performance in methane and ethane adsorption. Therefore, the HKUST-1 material produced in MW fields for 3 min only shows the highest phase purity and the largest surface area (BET) and porosity, along with a rather small crystallite size (below ~300 nm), demonstrating high methane and ethane adsorption capacity in the pressure range 1–30 atm.

Spectroscopic Probing Of Mn-Doped ZnO Nanowires Synthesized via a Microwave-Assisted Route

Dilute magnetic semiconductors such as transition-metal-doped ZnO are potential candidates for spintronic applications. Transition metals such as Mn, Fe, and Cu when doped in ZnO enable spin magnetic properties to conventional semiconductors. Although several techniques such as wet chemical and vapor deposition methods are employed to achieve homogeneous doping in ZnO, these methods have limits pertaining to solubility levels of dopant ion, morphology, competition between intrinsic and extrinsic defects and localization of the defect species. This manuscript is an addition to the vast knowledge of methods and protocols that present the synthesis of transition-metal-doped ZnO. In this report, manganese-doped ZnO is synthesized via a microwave-assisted hydrolysis technique. The defect structure of Mn-doped ZnO wires is investigated via electron paramagnetic resonance and photoluminescence techniques. The analysis indicates that Mn2+ substitutes the Zn ion and dominates the intrinsic defect species in ZnO.

Herbal transdermal patches made from optimized polyvinyl alcohol blended film: Herbal extraction process, film properties, and in vitro study

Herbal transdermal patches were prepared by incorporating Lysiphyllum strychnifolium stem extract into optimized polyvinyl alcohol (PVA) blended film as a matrix layer for controlled drug release. A microwave-assisted technique was used for extracting L. strychnifolium stems. The optimum extraction conditions predicted by the Design-Expert® program were 80% of ethanol solvent, 800 W power, 20 s extraction time, and one extraction cycle. The prediction was accurate with a low percentage error. The total phenolics and total flavonoids of the herbal extract were 515.48 ± 43.08 and 59.78 ± 2.11 mg CE/g extract, respectively. Antioxidant activity of the herbal extract was 1.85 ± 0.12 and 0.533 ± 0.056 μg/ml from DPPH and FRAP assay, respectively. Nitric oxide scavenging assay of the herbal extract gave an IC50 of 114.42 ± 22.39 μg/mL. The blank optimized PVA blended film and herbal transdermal patches had desirable properties and compatible, homogeneous, smooth, and compact blended ingredients. The herbal transdermal patches could control the release and skin permeation behavior of astilbin from the matrix layer. The kinetics of the release and permeation behavior of astilbin were fitted to the Korsmeyer–Peppas and zero-order model, respectively. Thus, the transdermal patches containing L. strychnifolium extract are suitable for use in herbal medicine applications.

Exploration of microwaves for biorefining of phenolic antioxidants from Citrus reticulata peels: Spectrophotometric and spectroscopic analyses

Citrus industries discard an enormous waste as a by-product during juice processing, which is attracting researchers due to its functional/nutraceutical properties. To utilize the functional potential of kinnow peels, bioactives have been extracted using several green extraction techniques. In the present research, the microwave-assisted technique has been used to extract bioactive phytochemicals (phenolic and total antioxidants) from kinnow peels. Process variables, such as microwave power, solvent concentration, liquid to solid ratio (LSR), and time, were studied to maximize the extract yield of phenolic and antioxidant compounds from kinnow peels. Maximum phenolic content (2.48 mg GAE/g peels) with antioxidant activity of 63.20% and 6.38 mmol Fe2+/100 g peels for DPPH and FRAP assays, respectively, was observed at 300 W, 80% ethanol, and LSR of 50 ml/g after 6 min extraction time. The presence of phenolic and antioxidant compounds was confirmed by FT-IR and GC-EI MS techniques. Novelty impact statement Microwave-assisted extraction has emerged as an efficient non-contact heating extraction technique. But there is inadequate data on the valorization of kinnow processing by-products using microwave-assisted extraction. The present research has been conducted to investigate the effect of process parameters of microwave-assisted technique on the extraction of phenolic and antioxidant compounds from kinnow peels. This study could encourage the scale-up process for the value addition of agro-industrial waste by efficient extraction of bioactive compounds from citrus processing by-products.

Microwave-assisted extraction of sea buckthorn pomace and seed extracts as a proactive antioxidant to stabilize edible oils

Sea buckthorn, an ancient medicinal plant, is gaining attention because of its prodigious antioxidant activities. Microwave-assisted (MAE) and Soxhlet extraction techniques were attempted to obtain the extractives from sea buckthorn pomace and seed using low (n-hexane) and medium (ethanol) polar solvents aiming at higher extraction yield. The study's main purpose was to evaluate the efficacy of antioxidant activities (free radical scavenging activity) via electro paramagnetic resonance and oxidative stability through rancimat analysis for sea buckthorn seed and pomace extracts. The maximum extraction of 78.4 wt% and 59.9 wt% for pomace and seed, respectively, were obtained using a microwave reactor at temperature 80 °C and power 150 W with ethanol as solvent. A relative comparison of the MAE and conventional Soxhlet extraction yield revealed that MAE is effective in extracting more antioxidant compounds with higher yields. Further, ethanol extracted seed oil showed the highest (98%) 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical slaking at 5% (w/v) concentration. The oxidative stability of sea buckthorn pomace and seed extracts was found to be on par with butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) synthetic antioxidants when the extracts (3000 ppm) were blended and tested with canola oil.

Fluorescence turn-off sensing of TNT by polyethylenimine capped carbon quantum dots

In recent years, the determination of 2,4,6-trinitrotoluene (TNT) explosive residues in various matrices has attracted great interest from the perspective of national security and public health. Here, a fluorescent polyethylenimine capped carbon quantum dots (PEI-C-dots) probe was synthesized by a microwave-assisted technique using polyethylenimine and citric acid precursors and used to detect TNT. The sensing mechanism of TNT is based on fluorescence quenching as a result of the donor–acceptor interaction between Meisenheimer anion form of TNT and PEI on the PEI-C-dots surface. The fluorescence quantum yield of the synthesized PEI-C-dots was 54% and the detection limit for TNT was 93 μg/L. It was observed that neither the nitramine group (HMX and RDX) explosives with similar structures nor common soil ions and camouflage agents interfered with the determination of TNT. The interference effect of picric acid was eliminated by removing it with a basic anion exchanger before the determination. This nanosensor allows rapid, simple, selective, and sensitive determination of TNT residues in complex matrices and has the potential to be converted into a kit format.

Dielectric and mechanical properties of CaCu3Ti3.925(Nb0.5Al0.5)0.075O12 & Al reinforced epoxy-composites (0–3) for embedded capacitor applications

CaCu3Ti3.925(Nb0.5Al0.5)0.075O12 [CCTNAO] ceramics were synthesized by microwave assisted solid state reaction technique. CCTNAO ceramics possessed room temperature (RT) dielectric constant (εr) ∼ 24,173 with tanδ ∼0.149 at 1 kHz frequency. Commercially available epoxy-resin, hardener, Al-powder along with CCTNAO powder were used to prepare epoxy based 0–3 composites. Maximum εr ∼33.37 with tanδ ∼0.107 at RT were obtained for 40 vol% CCTNAO loading in epoxy. For x = 0.2 in (1-x)[0.8 Epoxy-0.2 CCTNAO]-x Al Epoxy composites, highest εr ∼77.6 with tanδ ∼ 0.15 at 1 kHz frequency were observed. Increase in εr with the increase of Al filler content in composites is attributed to interfacial polarization and cluster formations. Different theoretical models were discussed to explain the dielectric properties of synthesized composites. Experimentally measured values of εeff were in close agreement with EMT model (n = 0.13) and Yamada Model (η = 7). An empirical proposed power law εeff = εm(1+x)n, with n ∼ 10 had a considerable agreement with the experimental results. Vickers hardness test study was carried out to ascertain the mechanical properties of the synthesized composites.

Optimization and Evaluation of Ketoconazole Loaded Nanostructured Lipid Carriers Employing Microwave-Assisted Technique

The present research work is designed to formulate, optimize and evaluate the ketoconazole loaded nanostructured lipid carriers for the topical delivery. Ketoconazole loaded nanostructured lipid carriers were prepared by one pot single-step microwave assisted technique using Compritol® 888 ATO, Labrafac PG and soya lecithin employing 2-factors 3-level experimental design. The p-size of the optimized batch of microwave assisted ketoconazole loaded nanostructured lipid carriers was found to be 60.15 nm. The in vitro drug release in 24 h study showed the biphasic release pattern, initial burst release for 5 h followed by slower release upto 24 h. Furthermore, ex vivo skin permeation study revealed that 3670.99 μg/cm2 and 4644.78 μg/cm2 of drug permeated from ketoconazole loaded nanostructured lipid carriers hydrogel and marketed formulation with the flux rate of 305.91 μg/cm2/h and 387.06 μg/cm2/h, respectively at the end of 24 h. Confocal laser scanning microscope images demonstrated appreciable cell uptake of 5(6)-Carboxyfluorescein loaded nanostructured lipid carriers hydrogel compared to 5(6)-Carboxyfluorescein-loaded plain hydrogel. Optimized batch of nanostructured lipid carrier formulation produced by microwave assisted technique produced particles in nm range with narrow polydispersity index and high entrapment efficiency. X-ray study confirmed that the crystalline nature of ketoconazole changed to amorphous form in the process of nanostructured lipid carrier formulation and thermal behavior analyzed by differential scanning calorimetry confirmed inclusion of drug into lipid matrix in its amorphous form. After performing the optimization and evaluations of nanostructured lipid carriers it can be concluded that nanostructured lipid carriers bear the potential to be explored further for the topical and other pharmaceutical applications.

Local structural study of α-MoO3 micro-strips using synchrotron X-ray diffraction and X-ray Absorption Spectroscopy at Mo K-edge

The orthorhombic MoO3 micro-strips sample was synthesized using microwave assisted chemical co-precipitation technique. Synchrotron X-ray Diffraction (SXRD) pattern and Rietveld Refinement was used to estimate structural parameter, crystallite size of sample. It reveals that the synthesized sample MoO3 crystallized as an orthorhombic phase. X-ray Absorption Spectroscopy (XAS) measurement, which comprises both X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) techniques, have been carried out on Mo K-edge to probe the local structure of samples. Local structure is also confirmed from the SXRD and Raman spectra of sample. XAS measurement reveals that the first bond length of Mo-O and Mo-Mo is 1.69 and 3.42 Å in orthorhombic MoO3 respectively. Transmission electron microscopy and SAED patterns showed stripe-like structure and single-crystal formation of MoO3 respectively.

Facile synthesis of ZnNC derived from a ZIF-8 metal-organic framework by the microwave-assisted solvothermal technique as an anode material for lithium-ion batteries

A zeolitic imidazolate framework-8 (ZIF-8) electrode is a good candidate as an anode material.

Lower-temperature processing of potassium niobate films by microwave-assisted hydrothermal deposition technique

Lower-temperature processing of potassium niobate films by microwave-assisted hydrothermal deposition technique

MICROWAVE-ASSISTED SYNTHESIS OF Cr-DOPED Gd2O3 NANOSTRUCTURES AND INVESTIGATION ON MORPHOLOGY, OPTICAL, AND PHOTOLUMINESCENCE PROPERTIES

In the present study, pure and chromium (Cr)-doped gadolinium oxide (Gd2O3) nanostructures (NSs) (2%, 5%, and 8%) were successfully synthesized by a microwave-assisted solution process technique. The X-ray diffraction and scanning electron microscopy results revealed that single-phase crystals appeared in up to 8% of the Cr-doped NSs and a secondary phase of GdCr2O4 formed beyond an 8% increase in Cr concentration. The spherical-shaped morphology observed for Cr:Gd2O3 NSs had average particle sizes varying between 80 and 150 nm. The ultraviolet-visible spectroscopic results exhibited absorption maxima between 345.1 and 411. 1 nm and the Eg value decreased from 3.46 to 2.85 eV as the Cr concentration increased. The X-ray photoelectron spectroscopy results suggested that the Cr+3 ions were well incorporated into the Gd2O3 NSs, with a high-energy Gd 3d3/2 peak appearing at 1222 eV. The room temperature photoluminescence spectra exhibited a blue emission peak, which was found to increase with an increase in the Cr content. In addition, a broad emission peak appeared at 463.4-495.5 nm, which is characteristic for Cr insertion in Gd2O3 NSs; an increase in Cr+3 ions beyond 8% supressed the blue emission peak. The results strongly suggest that the Cr:Gd2O3 NSs form a new class of luminescent materials.

Microwave assisted drying and extraction technique; kinetic modelling, energy consumption and influence on antioxidant compounds of fenugreek leaves

Fenugreek leaves contains bioactive compounds, which are helpful in maintaining human health. These compounds are adversely affected in conventional drying methods. Therefore, this study was carried out to retain maximum amount of these components through microwave-assisted drying and extraction technique. The technique was optimized for simultaneous drying and extraction process for fenugreek leaves. The drying rate and drying time were influenced by the level of microwave power; time was reduced from 21 to 5 minutes, when microwave power was changed from 30 to 100 W. Unlikely, the drying rate increased from 1.79 to 4.56 ± 0.05 g/(100 g.min) with the change in power (30 to 100 W). Moreover, moisture ratio analysis determined that two term model was the best to demonstrate the fitness with experimental values. The energy consumption was lowest for 100W compared to other powers. Furthermore, comparison between microwave-based extraction and methanol-extraction indicated that the antioxidant activity was better preserved compared to conventional ones even at higher microwave power levels.

Influence of the nitrogen pots from graphitic carbon nitride with the presence of wrinkled silica-titania for photodegradation enhancement of 2-chlorophenol

An interlayer structure hybrid wrinkled silica titania (WST) loaded on graphitic carbon nitride (g-C3N4) was successfully constructed using facile microwave-assisted solid-state technique. The as-prepared materials were characterized using N2 adsorption-desorption, XRD, FESEM, UV–Vis DRS, FTIR, and TEM analysis. The photocatalytic degradation of 2-chlorophenol (2-CP) towards visible light illumination (150 mW/cm2) is following the sequence: 10 wt% WST@CN (91%) > 5 wt% WST@CN (65%) > g-C3N4 (63%) > 15 wt% WST@CN (58%) ˃ WST (50%). The supreme photocatalytic performance of 10 wt% WST@CN was owing to the WST morphology that more concealed between stacked layer of g-C3N4, as a consequence of the stronger interaction between “nitrogen pots” of the g-C3N4 and Si/Ti species of the 10 wt% WST, and thus, enhanced the efficiency of charge separation. These criteria provide better charge carrier mobility for enhanced visible light driven photocatalytic performance. The kinetic studies revealed that the photocatalytic degradation of 2-CP using 10 wt% WST@CN obeyed a model of pseudo-first order, with the surface reaction being the rate determining step. Subsequently, the scavenger study confirmed that hydroxyl radicals that absorbed on the catalyst surface play a major role over 10 wt% WST@CN as emerged from the mechanism of Z-scheme. It is notable that the interfacial of WST@CN composite could appear as an excellent catalyst for its useful application for endocrine disruptive wastewater treatment.