Hybrid porous material supported in a cellulose acetate polymeric membrane for the direct immersion thin-film microextraction of parabens in water.

A simple and sensitive direct immersion thin-film microextraction (DI-TFME) method based on MIL-101(Cr) modified with carbon nanofibers supported in cellulose acetate (CA-MIL-101(Cr)@CNFs) polymeric membrane was developed for the extraction and preconcentration of parabens in environmental water samples. A high-performance liquid chromatography-diode array detector (HPLC-DAD) was used for the determination and quantification of methylparaben (MP) and propylparaben (PP). The factors affecting the DI-TFME performance were investigated using central composite design (CCD). The linearity of the DI-TFME/HPLC-DAD method obtained under optimal conditions was 0.04-0.04-500 µg/L with a correlation coefficient (R2) greater than 0.99, respectively. The limits of detection (LOD) and quantification (LOQ) for methylparaben were 11 ng/L and 37 ng/L; for propylparaben, they were 13 ng/L and 43 ng/L, respectively. The enrichment factors were 93.7 and 123 for methylparaben and propylparaben. The intraday (repeatability) and interday (reproducibility) precisions expressed as relative standard deviations (%RSD) were less than 5%. Furthermore, the DI-TFME/HPLC-DAD method was validated using real water samples spiked with known concentrations of the analytes. The recoveries ranged from 91.5 to 99.8%, and intraday and interday trueness values were less than ±15%. The DI-TFME/HPLC-DAD approach was effectively used for the preconcentration and quantification of parabens in river water and wastewater samples.

Removal of methylene blue using MnO2@rGO nanocomposite from textile wastewater: Isotherms, kinetics and thermodynamics studies.

In this study, the adsorptive removal of methylene blue dye, which is commonly used in textile industries, was investigated using the MnO2@reduced graphene oxide (rGO) adsorbent. The sonication-assisted synthesis from rGO nanosheets and MnO2 nanoparticles resulted to the MnO2@rGO nanocomposite with improved physicochemical properties. The characterization results showed the improved surface area, porous structure and adsorption sites from the nitrogen adsorption-desorption studies, improved morphology from the Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) and the improved crystal structure from X-ray powder diffraction (XRD). The improved physicochemical properties on the MnO2@rGO nanocomposite played a significant role in enhancing the dye removal in textile wastewater. The equilibrium experimental data was best described by the Langmuir isotherm model with a maximum adsorption capacity of 156 mg g-1, suggesting a monolayer adsorption. The kinetic data best fitted the pseudo-second order kinetic model, suggesting a chemisorption adsorption process. The thermodynamic data (ΔG°, ΔH° and ΔS°) confirmed the feasibility, randomness and spontaneous nature of the adsorption process. The mechanism of adsorption involved the hydrogen bonding, π-π interactions and electrostatic interactions. The removal of methylene blue using MnO2@rGO nanocomposite in spiked textile wastewater yielded a 98-99% removal. The method demonstrated competitiveness when compared with literature reported results, paving way for further investigations towards industrial scale applications.

Combination of zeolitic imidazolate framework-67 and magnetic porous porphyrin organic polymer for preconcentration of neonicotinoid insecticides in river water.

A nanostructured material composed of zeolitic imidazolate framework-67 and magnetic porous porphyrin organic polymer (ZIF-67@MPPOP) was successfully synthesized and applied for the enrichment of neonicotinoid insecticides in river water. The analytes were detected and quantified using high performance liquid chromatography coupled with diode array detector (HPLC-DAD) and liquid chromatography mass spectrometry (LC-MS). Influential experimental parameters were optimized using response surface methodology based on Box Behnken design. The adsorption capacities were 69.46, 80.53, 85.39 and 90.0 mg g-1 for thiamethoxam, imidacloprid, acetamiprid and clothianidin, respectively. At optimal experimental conditions, low limit of detection (LOD), limit of quantification (LOQ) and linearity were 0.0091-0.04 µg L-1, 0.04-0.13 µg L-1 and (0.04-600 µg L-1), respectively. The relative standard deviation used to evaluate the reproducibility and repeatability of the method was less than 5%. Finally, the method was employed for determination of four neonicotinoid insecticides in river water.

Adsorptive Removal of Cd, Cu, Ni and Mn from Environmental Samples Using Fe3O4-Zro2@APS Nanocomposite: Kinetic and Equilibrium Isotherm Studies.

In this study, Fe3O4-ZrO2 functionalized with 3-aminopropyltriethoxysilane (Fe3O4-ZrO2@APS) nanocomposite was investigated as a nanoadsorbent for the removal of Cd(II), Cu(II), Mn (II) and Ni(II) ions from aqueous solution and real samples in batch mode systems. The prepared magnetic nanomaterials were characterized using X-ray powder diffraction (XRD), scanning electron microscopy/energy dispersion x-ray (SEM/EDX) Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Factors (such as adsorbent dose and sample pH) affecting the adsorption behavior of the removal process were studied using the response surface methodology. Under optimized condition, equilibrium data obtained were fitted into the Langmuir and Freundlich isotherms and the data fitted well with Langmuir isotherms. Langmuir adsorption capacities (mg/g) were found to be 113, 111, 128, and 123 mg/g for Cd, Cu, Ni and Mn, respectively. In addition, the adsorption kinetics was analyzed using five kinetic models, pseudo-first order, pseudo-second order, intraparticle diffusion and Boyd models. The adsorbent was successfully applied for removal of Cd(II), Cu(II), Mn (II) and Ni(II) ions in wastewater samples.

Magnetic Mesoporous Carbon/ß-Cyclodextrin-Chitosan Nanocomposite for Extraction and Preconcentration of Multi-Class Emerging Contaminant Residues in Environmental Samples.

This study reports the development of magnetic solid-phase extraction combined with high-performance liquid chromatography for the determination of ten trace amounts of emerging contaminants (fluoroquinolone antibiotics, parabens, anticonvulsants and ß-blockers) in water systems. Magnetic mesoporous carbon/ß-cyclodextrin-chitosan (MMPC/Cyc-Chit) was used as an adsorbent in dispersive magnetic solid-phase extraction (DMSPE). The magnetic solid-phase extraction method was optimized using central composite design. Under the optimum conditions, the limits of detection (LODs) ranged from 0.1 to 0.7 ng L-1, 0.5 to 1.1 ng L-1 and 0.2 to 0.8 ng L-1 for anticonvulsants and ß-blockers, fluoroquinolone and parabens, respectively. Relatively good dynamic linear ranges were obtained for all the investigated analytes. The repeatability (n = 7) and reproducibility (n = 5) were less than 5%, while the enrichment factors ranged between 90 and 150. The feasibility of the method in real samples was assessed by analysis of river water, tap water and wastewater samples. The recoveries for the investigated analytes in the real samples ranged from 93.5 to 98.8%, with %RSDs under 4%.

Magnetic Fe3O4@Mg/Al-layered double hydroxide adsorbent for preconcentration of trace metals in water matrices.

A magnetic Fe3O4@MgAl-layered double hydroxide (MLDH) nanocomposite was successfully synthesized and applied as an effective adsorbent for preconcentration of trace As(III), Cd(II), Cr(III), Co(II), Ni(II), and Pb(II) ions from complex matrices. The quantification of the analytes was achieved using the inductively coupled plasma optical emission spectrometry (ICP-OES) technique. The nanocomposite was then characterized using BET, FTIR, SEM, and EDS. Due to its high adsorption surface area, compared to traditional metal oxide-based adsorbents, MLDH nanocomposite exhibited high extraction efficiency. Several experimental parameters controlling the preconcentration of the trace metals were optimized using response surface methodology based on central composite design. Under optimum conditions, the linearity ranged from 0.1 to 500 µg L-1 and the correlation of coefficients (R2) were higher than 0.999. The limits of detection (LODs) and quantification (LOQs) were 0.11-0.22 µg L-1 and 0.35-0.73 µg L-1, respectively. The intra-day (n = 10) and inter-day precisions (n = 5 working days) expressed in the form of percent relative standard deviations (%RSDs) were below 5%. The proposed method was successfully applied for the analysis of the As(III), Cd(II), Cr(III), Co(II), Ni(II), and Pb(II) ions in different environmental water samples.

Beta-Cyclodextrin-Decorated Magnetic Activated Carbon as a Sorbent for Extraction and Enrichment of Steroid Hormones (Estrone, ß-Estradiol, Hydrocortisone and Progesterone) for Liquid Chromatographic Analysis.

A ß-cyclodextrin-decorated magnetic activated carbon adsorbent was prepared and characterized using various analytical techniques (X-ray diffraction (XRD), scanning electron microscopy-electron diffraction spectroscopy (SEM-EDS) and transmission electron microscopy (TEM)), and the adsorbent was used in the development of a magnetic solid-phase microextraction (MSPE) method for the preconcentration of estrone, ß-estradiol, hydrocortisone and progesterone in wastewater and river water samples. This method was optimized using the central composite design in order to determine the experimental parameters affecting the extraction procedure. The quantification of hormones was achieved using high-performance liquid chromatography equipped with a photodiode array detector (HPLC-DAD). Under optimum conditions, the linearity ranged from 0.04 to 300 µg L-1 with a correlation of determinations of 0.9969-0.9991. The limits of detection and quantification were between 0.01-0.03 and 0.033-0.1 µg L-1, with intraday and interday precisions at 1.1-3.4 and 3.2-4.2. The equilibrium data were best described by the Langmuir isotherm model, and high adsorption capacities (217-294 mg g-1) were obtained. The developed procedure demonstrated high potential as an effective technique for use in wastewater samples without significant interferences, and the adsorbent could be reused up to eight times.

Magnetic Solid Phase Extraction Based on Nanostructured Magnetic Porous Porphyrin Organic Polymer for Simultaneous Extraction and Preconcentration of Neonicotinoid Insecticides From Surface Water.

In this study, a magnetic porphyrin-based porous organic polymer (MP-POP) nanocomposite was successfully synthesized according previous studies and applied as an adsorbent for simultaneous extraction and preconcentration of four neonicotinoid insecticides from surface river water. The MP-POP was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDS), N2-adsorption/desorption analysis, Fourier Transform infrared spectroscopy (FTIR). The neonicotinoid insecticides were quantified using high performance chromatography coupled with diode array detector (HPLC-DAD). The MP-POP shown to have a high surface area, highly porous structure and strong affinity toward the investigated analytes. The adsorption capacities were 99.0, 85.5, 90.0, and 79.4 mg g-1 for acetamiprid, clothiandin, thiacloprid and imidacloprid, respectively. The influential parameters affecting the magmatic µ-solid phase extraction (M-µ-SPE) procedure were investigated using fractional factorial design and surface response methodology (RSM). Under optimum conditions, the method exhibited relatively low limit of detection in the range of 1.3-3.2 ng L-1, limit of quantification in the range of 4.3-11 ng L-1 and wide linearity (up to 600 µg L-1). The intraday and interday precision, expressed as the relative standard deviation (RSD) were <5%. The percentage recoveries for the four target analytes ranged from 91 to 99.3% for the spiked river water samples. The method was applied for determination of neonicotinoids in river water samples and concentrations ranged from 0 to 190 ng L-1.

Ultrasound-assisted dispersive solid phase nanoextraction of selected personal care products in wastewater followed by their determination using high performance liquid chromatography-diode array detector.

This study reports a rapid and simple method based on ultrasound-assisted dispersive solid phase nanoextraction (UA-SPNE) method for the extraction and preconcentration of selected personal care products using MPC@Al2O3-SiO2 nano adsorbent. A high performance liquid chromatograph equipped with a diode array detector (HPLC-DAD) was used to detect the analytes of interest. Experimental parameters affecting the extraction and preconcentration efficiency of the UA-SPNE (such as mass of adsorbent, extraction time, sample pH and eluent volume,) were optimized using fractional factorial design and response surface methodology based on central composite design. Under optimized conditions, the linear range for benzophenone, N,N-diethyl-3-methylbenzamide and trichlorocarbanilide were in the interval of LOQ-1000 µg L-1 with correlation coefficients ranged from 0.9907 to 0.9977. The limits of detection and limits of quantification were 0.066-0.096 µg L-1 and 0.22-0.32 µg L-1, respectively. The accuracy of the UA-SPNE/HPLC-DAD method was evaluated using spike recovery test and the recoveries were in the range of 98-107%. The repeatability and reproducibility of the method 0.8-1.0 % and 2.4-4.4%, respectively.

Adsorptive removal of lead from acid mine drainage using cobalt-methylimidazolate framework as an adsorbent: kinetics, isotherm, and regeneration.

In this work, cobalt-methylimidazolate framework has been used as an adsorbent in the removal of Pb(II) from acid mine drainage in adsorption batch system. X-ray diffraction, Fourier-transform infrared spectroscopy, Brunauer-Emmet-Teller and transmission electron microscope were used for structural, morphological, and surface characteristics of cobalt-methylimidazolate framework. The concentration of heavy metal ions in water samples was measured by inductively coupled plasma optical emission spectrometry. Different experimental factors/variables (such as contact time, dosage, and pH) affecting the adsorption of Pb(II) from acid mine drainage were optimized by response surface methodology based on central composite design. Under optimized experimental parameters, the maximum adsorption capacity of Pb(II) was found to be 105 mg g-1. The nature of the adsorption process was investigated using Langmuir and Freundlich isotherm models. The obtained data best fitted Langmuir isotherm model suggesting a homogeneous adsorption process. Furthermore, the adsorption mechanism was investigated using five kinetic models, that is, pseudo-first order, pseudo-second order, intraparticle diffusion and Elovich model. The adsorption data fitted better to pseudo-second-order followed by intra-particle diffusion kinetic models suggesting that the adsorption mechanism is dominated by both chemical and physical adsorption processes. The adsorbent could be regenerated up to 8 cycles and it was successfully used in the removal of lead in real acid mine drainage samples.

In-Syringe Micro Solid-Phase Extraction Method for the Separation and Preconcentration of Parabens in Environmental Water Samples.

In this study, a simple, rapid and effective in-syringe micro-solid phase extraction (MSPE) method was developed for the separation and preconcetration of parabens (methyl, ethyl, propyl and butyl paraben) in environmental water samples. The parabens were determined and quantified using high performance liquid chromatography and a photo diode array detector (HPLC-PDA). Chitosan-coated activated carbon (CAC) was used as the sorbent in the in-syringe MSPE device. A response surface methodology based on central composite design was used for the optimization of factors (eluent solvent type, eluent volume, number of elution cycles, sample volume, sample pH) affecting the extraction efficiency of the preconcentration procedure. The adsorbent used displayed excellent absorption performance and the adsorption capacity ranged from 227⁻256 mg g−1. Under the optimal conditions the dynamic linear ranges for the parabens were between 0.04 and 380 µg L−1. The limits of detection and quantification ranged from 6⁻15 ng L−1 and 20⁻50 ng L−1, respectively. The intraday (repeatability) and interday (reproducibility) precisions expressed as relative standard deviations (%RSD) were below 5%. Furthermore, the in-syringe MSPE/HPLC procedure was validated using spiked wastewater and tap water samples and the recoveries ranged between from 96.7 to 107%. In conclusion, CAC based in-syringe MSPE method demonstrated great potential for preconcentration of parabens in complex environmental water.

Adsorptive removal of microcystin-LR from surface and wastewater using tyre-based powdered activated carbon: Kinetics and isotherms.

Microcystin LR (MC-LR) is a highly toxic compound and it is known for its adverse health effect on both humans and animals. Due to the ineffectiveness of conventional water treatments methods, for the past decades, researchers have been developing cost-effective ways of removing MC-LR from water bodies. This study reports the application of powdered activated carbon (PAC) obtained from the waste tyre for the removal of MC-LR. The choice of the adsorbent was chosen due to its attractive properties. The prepared tyre-based PAC was found to have the large surface area (1111 m2 g-1). The detection of MC-LR was achieved using high performance liquid chromatography (HPLC) coupled with a PDA detector. The experimental parameters (such as optimum pH, dosage and contact time) affecting the removal of MC-LR using tyre based-powdered activated carbon were optimized using response surface methodology (RSM). Maximum removal of MC-LR was achieved under the following optimum conditions; sample pH 4, carbon dosage concentration 10,000 mg L-1 and contact time of 34 min. Under optimum conditions, kinetic studies and adsorption isotherms reflected better fit for pseudo-second-order rate and Langmuir isotherm model, respectively. The optimized method was applied for the removal of MC-LR in wastewater sample. The effluent and influent sample contained initial concentrations ranging from 0.52 to 8.54 µg L-1 and the removal efficiency was 100%.

Microwave assisted solid phase extraction for separation preconcentration sulfamethoxazole in wastewater using tyre based activated carbon as solid phase material prior to spectrophotometric determination.

This work was chiefly encouraged by the continuous consumption of antibiotics which eventually pose harmful effects on animals and human beings when present in water systems. In this study, the activated carbon (AC) was used as a solid phase material for the removal of sulfamethoxazole (SMX) in wastewater samples. The microwave assisted solid phase extraction (MASPE) as a sample extraction method was employed to better extract SMX in water samples and finally the analysis of SMX was done by the UV-Vis spectrophotometer. The microwave assisted solid phase extraction method was optimized using a two-level fractional factorial design by evaluating parameters such as pH, mass of adsorbent (MA), extraction time (ET), eluent ratio (ER) and microwave power (MP). Under optimized conditions, the limit of detection (LOD) and limit of quantification (LOQ) were 0.5µgL-1 and 1.7µgL-1, respectively, and intraday and interday precision expressed in terms of relative standard deviation were >6%.The maximum adsorption capacity was 138mgg-1 for SMX and the adsorbent could be reused eight times. Lastly, the MASPE method was applied for the removal of SMX in wastewater samples collected from a domestic wastewater treatment plant (WWTP) and river water.