Optimization using response surface methodology for fast removal of hazardous azo dye by γ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>@CuO nanohybrid synthesized by sol–gel combustion

An efficient adsorption system was developed for removal of hazardous Direct Blue 71 as a sample azo dye. The γ-Fe₂O₃@CuO adsorption system was synthesized based on a sol–gel combustion route and characterized by energy-dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) analysis, vibrating-sample magnetometry (VSM), and field-emission scanning electron microscopy (FESEM) techniques. The response surface methodology with Box–Behnken design was used to evaluate the effects of pH, shaking time, and adsorbent dose on dye adsorption. The results showed that solution pH was the parameter with greatest effect on dye adsorption. Adsorption equilibrium was reached quickly, within 8 min. Study of isotherms revealed adsorption capacity of 45.7 mg g^?1 according to the Freundlich model. Sorbent regeneration could be performed using methanol–NaOH (0.1 mol L^?1) solution.     

Polyhydroxyquinoline-carbon nanotube chelating resin for selective adsorption of lead ions: multivariate optimization,isothermic, and thermodynamic study

In this work a facile hydrothermal route has been employed to prepare a multiwall carbon nanotube wrapped in a chelating resin. 8-Hydroxyquinoline and p-formaldehyde were used as monomer and linker for polymer synthesis. The prepared composite was employed as an efficient adsorbent for lead adsorption and preconcentration from various matrices. Effective parameters on lead adsorption have been optimized by central composite design. Results showed that equilibrium adsorption was obtained at pH = 4, with a shacking time of 15 min and adsorbent dosage of 15 mg. Isotherm study showed that the sorbent has adsorbent capacity of 250 mg g^?1; moreover, the process followed a Langmuir isotherm model. Thermodynamic investigation confirmed that lead adsorption is spontaneous, as well as follows endothermic path.     

Preconcentration of cobalt ions by a melamine-modified cellulose@MWCNT nanohybrid

Melamine functionalized cellulose@carbon nanotubes were prepared by the following method: (a) Cellulose was dissolved in a mixture of urea and NaOH solutions and then mixed with multiwall carbon nanotubes; (b) the MWCT-modified cellulose was precipitated by addition of water; (c) the MWCNTs were activated with thionyl chloride, and finally reacted with melamine. The resulting sorbent was used in preconcentration of Co(II) ions prior to their determination by flame atomic absorption spectroscopy. The sorbent was characterized by FTIR and field emission scanning electron microscopy. The effects of the pH value of the medium, contact time, and elution conditions were optimized. The calibration plot is linear in the 3 to 200 μg·L￣¹ Co(II) concentration range, the limit of detection is 0.8 μg·L￣¹, and the relative standard deviation (at a concentration of 100 μg·L￣¹) is 3.5 %. The maximum sorption capacity is 167 mg·g￣¹. The method was applied to the preconcentration of cobalt ions from (spiked) food and water samples and gave recoveries between 96 and 102 %.

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Graphical abstract A composite of the type melamine - cellulose/MWCNT was used for fast preconcentration of cobalt ions.

     

Bifunctional aminosilane-functionalized Fe3O4 nanoparticles as efficient sorbent for preconcentration of cobalt ions from food and water samples

Research on Chemical Intermediates - Magnetic Fe3O4 nanoparticles were synthesized by a coprecipitation method, then their surface was covered and modified by...     

Oxidative dimerization of thiols to disulfide using recyclable magnetic nanoparticles

Research on Chemical Intermediates - Dimerization of thiol groups to disulfide is an important transformation in chemical processes. In this study, magnetic ion exchanged Montmorillonite-k10 was...     

A New Type of Euler Polynomials and Numbers

By defining two specific exponential generating functions, we introduce a kind of Euler polynomials and study its basic properties in detail. As an application of the introduced polynomials, we use them in computing some new series of Taylor type that contain the associated Euler numbers \(E_n(0)\) where \(E_n(x)\) is the Euler polynomial.     

Solid phase extraction of hexavalent chromium by Mannich base polymer wrapped flower-like layered double hydroxide

In the present work, synthesis of polymer wrapped flower-like MgAl layered double hydroxide was done through condensation of 1,4 phenylenediamine and resorcinol by p-formaldehyde. The nanocomposite was characterised with X-ray diffraction analysis, fourier transform infrared spectroscopy, thermogravimetric analysis and field emission scanning electron microscopy techniques and employed for effective adsorption of Cr(VI) from aqueous solution prior to flame atomic absorption spectrometer determination. Optimum level of effective parameters (pH, reaction time and adsorbent dosage) and their interaction was determined by response surface methodology. To investigate applicability of method for trace heavy metal adsorption, the method was employed for preconcentration of Cr(VI) in water samples. At the optimum conditions, pH = 4.5, shaking time of 15 min and adsorbent dosage of 20 mg, analytical performance of the method was evaluated and results showed that calibration curve is linear in the concentration range of 2–100 μg L^?1. Moreover, limit of detection was 0.22 µg L^?1 and relative standard deviation of six replicate experiments at initial concentration of 0.1 mg L^?1 was 3.3%. Isotherm study showed that Freundlich model can better describe adsorption behaviour as well as the sorbent showed the adsorption capacity of 62.5 mg g^?1. Moreover, thermodynamic study revealed that chromate adsorption was spontaneous and followed the endothermic path. Regeneration of sorbent was performed using 1.0 mol L^?1 of NaOH solution. The sorbent was employed for Cr(VI) determination from food additives and seawater samples.     

Facile synthesis of Fe3O4/MoS2 nanohybrid for solid phase extraction of Ag(I) and Pb(II): kinetic,isotherm and thermodynamic studies

Recently, MoS₂ with abundant electron density in its structure attracted more attention as an adsorbent for environmental remediation. However, hard manipulation of target solution owing to high dispersibility in aqueous media restricts its application as adsorbent. Preparation of Fe₃O₄/MoS₂ nanohybrid can solve this problem. Also, this nanohybrid improves adsorption capacities of target ions. In this work, Fe₃O₄ nanoparticles, MoS₂ nanosheets and hybrid of these two were synthesised and then characterised by X-ray diffraction, energy-dispersive X-ray spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, Fourier transforms infrared spectra, Brunauer–Emmett–Teller surface area and vibrating sample magnetometer. Subsequently, adsorption of Ag(I) and Pb(II) ions from aqueous solution by these three adsorbents was examined in detail and compared with each other while the adsorption conditions including the pH value, contact time, dosage of sorbent, elution conditions and interfering ions have been optimised. According to obtained results, prepared nanohybrid showed enhanced adsorption capacities for both ions relative to naked Fe₃O₄ and MoS₂. The limits of detection for Ag(I) and Pb(II) were calculated as 0.49 µg L^?1 and 2.7 µg L^?1, respectively, and the relative standard deviation percentages (n = 5) for Ag(I) and Pb(II) were 2.8%, and 3.0%, respectively. Furthermore, the preconcentration factors were 300 and 75 for Ag(I) and Pb(II) ions, respectively. Moreover, kinetic studies showed that pseudo-second-order model can better describe target analytes adsorption properties by every three adsorbents. Regeneration of the adsorbents was performed with HCl/thiourea mixture.     

Development of an efficient enrichment system for copper determination in water and food samples based on p-phenylenediamine anchored magnetic titanium dioxide nanowires

In the present work, titanium dioxide nanowires (TNWs) were synthesised via hydrothermal method. Insertion of ZnFe₂O₄ nanoparticles to the surface of TNWs was done by sol gel combustion synthesis of the nanoparticles in the presence of the nanowires. The surface of prepared magnetic TNWs was modified by p-phenylendiamine and then it was used in preconcentration of Cu²⁺ ion prior to their determination by flame atomic absorption spectroscopy. The sorbent was characterised by Fourier transform infrared spectra, EDX, FE-SEM and VSM techniques. We investigated and optimised various parameters influencing the preconcentration efficiency, such as the media pH, adsorbent quantity, contact time, sample volume and elution conditions. Under optimum conditions, the analytical performance of the method was evaluated. The calibration curve was found to be linear from 10.0 to 150 μg L^?1 (R² = 0.996). Calculated limit of detection was 0.43 μg L^?1 (n = 5). The estimated relative standard deviation was 2.50% (n = 5). Moreover, the maximum adsorption capacity of the sorbent was 51.5 mg g^?1 and preconcentration factor was 125. Capability of developed method was proved by applying it for preconcentration of Cu²⁺ ion from food and water samples.