Exploring the performance of magnetic methacrylic acid-functionalized β-cyclodextrin adsorbent toward selected phenolic compounds

In this study, the removal of bisphenol A (BPA), 2,4-dinitrophenol (2,4-DNP), and 2,4-dichlorophenol (2,4-DCP) using a new magnetic adsorbent methacrylic acid-functionalized β-cyclodextrin (Fe3O4@MAA-βCD) was evaluated. The materials were characterized by Fourier transform infrared spectroscopy, scanning electron microscope, transmission electron microscopy, and X-ray diffraction. The batch adsorption experiments optimized and evaluated various operational parameters such as pH, contact time, sorbent dosage, initial concentration, and temperature. The result shows that DNP possessed the most excellent affinity toward Fe3O4@MAA-βCD adsorbents compared to BPA and DCP. Also, BPA showed the lowest removal and was used as a model analyte for further study. The adsorption kinetic data revealed that the uptake of these compounds follows the pseudo-second order. Freundlich and Halsey isotherms best-fitted the adsorption equilibrium data. The desorption process was exothermic and spontaneous, and a lower temperature favored the adsorption. Furthermore, hydrogen bonding, inclusion complexion, and π–π interactions contributed to the selected phenolic compound’s adsorption.

Removal of bisphenol A from aqueous media using a highly selective adsorbent of hybridization cyclodextrin with magnetic molecularly imprinted polymer

In this study, a unique magnetic molecularly imprinted polymer (MMIP) adsorbent towards bisphenol A (BPA) as a template molecule was developed by bulk polymerization using β-cyclodextrin (β-CD) as a co-monomer with methacrylic acid (MAA) to form MMIP MAA-βCD as a new adsorbent. β-CD was hybridized with MAA to obtain water-compactible imprinting sites for the effective removal of BPA from aqueous samples. Benzoyl peroxide and trimethylolpropane trimethacrylate were used as the initiator and cross-linker, respectively. The adsorbents were characterized by Fourier transform infrared spectroscopy, scanning electronic microscopy, transmission electron microscopy, vibrating sample magnetometer, Brunauer-Emmett-Teller and X-ray diffraction. 1H nuclear magnetic resonance spectroscopy was used to characterize the MAA-βCD and BPA-MAA-βCD complex. Several parameters influencing the adsorption efficiency of BPA such as adsorbent dosage, pH of sample solution, contact time, initial concentrations and temperature as well as selectivity and reusability study have been evaluated. MMIP MAA-βCD showed significantly higher removal efficiency and selective binding capacity towards BPA compared to MMIP MAA owing to its unique morphology with the presence of β-CD. The kinetics data can be well described by the pseudo second-order kinetic and Freundlich isotherm and Halsey models best fitted the isotherm data. The thermodynamic studies indicated that the adsorption reaction was a spontaneous and exothermic process. Therefore, MMIP based on the hybrid monomer of MAA-βCD shows good potential of a new monomer in molecularly imprinted polymer preparation and can be used as an effective adsorbent for the removal of BPA from aqueous solutions.

Development of a new efficient and economical magnetic sorbent silicone surfactant-based activated carbon for the removal of chloro- and nitro-group phenolic compounds from contaminated water samples

In this study, activated carbon (AC) coated with a green silicone surfactant (SS) was further incorporated with magnetite particles (Fe₃O₄) via a co-precipitation method to enhance the separation of the newly designed magnetic AC–SS (Fe₃O₄@AC–SS) in a magnetic field. The properties of this magnetic adsorbent were characterized via Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The adsorption characteristics of the Fe₃O₄@AC–SS adsorbent were examined using 2,4-nitrophenol and 2,4-dichlorophenol as adsorbates. Experiments were performed to investigate the adsorption kinetics, isotherms, thermodynamics as well as the effects of adsorption dosage and solution pH on the removal of both analytes. The kinetic data were well-fitted by the pseudo-second order model and the Freundlich model best described the adsorption isotherm for both analytes. The maximum adsorption capabilities for 2,4-dinitrophenol and 2,4-dichlorophenol reached 43 and 98 mg g⁻¹, respectively. The analysis was further validated using real industrial effluent, and a removal efficiency of 62.2–98.1% and relative standard deviation value less than 7.2% were attained for both analytes. Thus, the multifunctional adsorbent has potential to function as an adsorbent for the fast, convenient, economical and highly efficient removal of pollutants from wastewater, which is significant for the purification of natural water and industrial effluent.

In this study, activated carbon (AC) coated with a green silicone surfactant (SS) was further incorporated with magnetite particles (Fe₃O₄) to enhance the separation of the newly designed magnetic AC–SS (Fe₃O₄@AC–SS) in a magnetic field.

β-Cyclodextrin conjugated bifunctional isocyanate linker polymer for enhanced removal of 2,4-dinitrophenol from environmental waters

In this work, we reported the synthesis, characterization and adsorption study of two β-cyclodextrin (βCD) cross-linked polymers using aromatic linker 2,4-toluene diisocyanate (2,4-TDI) and aliphatic linker 1,6-hexamethylene diisocyanate (1,6-HDI) to form insoluble βCD-TDI and βCD-HDI. The adsorption of 2,4-dinitrophenol (DNP) on both polymers as an adsorbent was studied in batch adsorption experiments. Both polymers were well characterized using various tools that include Fourier transform infrared spectroscopy, thermogravimetric analysis, Brunauer-Emmett-Teller analysis and scanning electron microscopy, and the results obtained were compared with the native βCD. The adsorption isotherm of 2,4-DNP onto polymers was studied. It showed that the Freundlich isotherm is a better fit for βCD-TDI, while the Langmuir isotherm is a better fit for βCD-HMDI. The pseudo-second-order kinetic model represented the adsorption process for both of the polymers. The thermodynamic study showed that βCD-TDI polymer was more favourable towards 2,4-DNP when compared with βCD-HDI polymer. Under optimized conditions, both βCD polymers were successfully applied on various environmental water samples for the removal of 2,4-DNP. βCD-TDI polymer showed enhanced sorption capacity and higher removal efficiency (greater than 80%) than βCD-HDI (greater than 70%) towards 2,4-DNP. The mechanism involved was discussed, and the effects of cross-linkers on βCD open up new perspectives for the removal of toxic contaminants from a body of water.

Formulation of chelating agent with surfactant in cloud point extraction of methylphenol in water

Cloud point extraction (CPE) is a separation and preconcentration of non-ionic surfactant from one liquid phase to another. In this study, Sylgard 309 and three different types of additives for CPE, namely CPE-Sylgard, CPE-Sylgard-BMIMBr and CPE-Sylgard-GLDA, are investigated to extract methylphenol from water samples. The methylphenols are well separated by reversed-phase high-performance liquid chromatography (HPLC) with isocratic elution of acetonitrile : water; 60 : 40 (v/v) and detection at 260 nm. The optimized parameters for the effect of salt, surfactant, temperature, time of extraction, pH, interference study and the performance of different additives on methylphenol extraction are investigated. CPE-Sylgard-GLDA is chosen because it gives us a high peak and good peak area compared with CPE-Sylgard and CPE-Sylgard-BMIMBr. The recovery extractions of CPE-Sylgard-GLDA are obtained in the range of 80-99% as the percentage of relative standard deviation (RSD) is less than 10. The LOD and LOQ are 0.05 ppm and 0.18 ppm, respectively. The method developed for CPE-Sylgard-GLDA coupled with HPLC is feasible for the determination of methylphenol because it is simple, effective, cheap, and produces a high percentage of recovery.

Correction to 'Determination of carcinogenic herbicides in milk samples using green non-ionic silicone surfactant of cloud point extraction and spectrophotometry'

[This corrects the article DOI: 10.1098/rsos.171500.].

Determination of carcinogenic herbicides in milk samples using green non-ionic silicone surfactant of cloud point extraction and spectrophotometry

A new cloud point methodology was successfully used for the extraction of carcinogenic pesticides in milk samples as a prior step to their determination by spectrophotometry. In this work, non-ionic silicone surfactant, also known as 3-(3-hydroxypropyl-heptatrimethylxyloxane), was chosen as a green extraction solvent because of its structure and properties. The effect of different parameters, such as the type of surfactant, concentration and volume of surfactant, pH, salt, temperature, incubation time and water content on the cloud point extraction of carcinogenic pesticides such as atrazine and propazine, was studied in detail and a set of optimum conditions was established. A good correlation coefficient (R² ) in the range of 0.991-0.997 for all calibration curves was obtained. The limit of detection was 1.06 µg l^-1 (atrazine) and 1.22 µg l^-1 (propazine), and the limit of quantitation was 3.54 µg l^-1 (atrazine) and 4.07 µg l^-1 (propazine). Satisfactory recoveries in the range of 81-108% were determined in milk samples at 5 and 1000 µg l^-1, respectively, with low relative standard deviation, n = 3 of 0.301-7.45% in milk matrices. The proposed method is very convenient, rapid, cost-effective and environmentally friendly for food analysis.

Performance evaluation of non-ionic silicone surfactants OFX 0309 and DC 193C as a new approach in cloud point extraction – spectrophotometry for determination of atrazine in water samples

Cloud point extraction (CPE) – spectrophotometric method had been adopted for the separation of atrazine using the non-ionic silicone surfactant, polysiloxane polyether, as a new approach of atrazine extractor in CPE. There were two types of polysiloxane polyether (DC 193C and OFX 0309) studied to investigate the effectiveness of these surfactants toward atrazine in CPE method. Various effects of operating parameters such as the concentration of surfactant and atrazine, addition of salt and change of temperature and pH on the extraction of atrazine have been studied in detail to find the optimum conditions. The limit of detections (LODs) and quantifications (LOQs) were in the range of 0.09–0.59 μg L⁻¹ and 0.31–1.95 μg L⁻¹ in water samples, respectively. The method recoveries at two spiked levels were 84–105% (CPE-OFX 0309) and 59–69% (CPE-DC 193C) with good correlation of determination (R²) ranging from 0.9927–0.9993 for both methods. The Langmuir isotherm has been used for solubilisation study of surfactant and atrazine. The thermodynamic parameters have been determined such as Gibbs free energy (ΔG°) which increases with temperature, value of enthalpy (ΔH°) and value of entropy (ΔS°) which increase with the surfactant hydrophobicity.

The principle of cloud point extraction (CPE) adopted for the separation of atrazine.

Optimization of a greener method for removal phenol species by cloud point extraction and spectrophotometry

A greener method based on cloud point extraction was developed for removing phenol species including 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and 4-nitrophenol (4-NP) in water samples by using the UV-Vis spectrophotometric method. The non-ionic surfactant DC193C was chosen as an extraction solvent due to its low water content in a surfactant rich phase and it is well-known as an environmentally-friendly solvent. The parameters affecting the extraction efficiency such as pH, temperature and incubation time, concentration of surfactant and salt, amount of surfactant and water content were evaluated and optimized. The proposed method was successfully applied for removing phenol species in real water samples.