Solid Phase Extraction Of Cr Research Articles

Cr(III) Ion-Imprinted Hydrogel Membrane for Chromium Speciation Analysis in Water Samples.

Novel Cr(III)-imprinted poly(vinyl alcohol)/sodium alginate/AuNPs hydrogel membranes (Cr(III)-IIMs) were obtained and characterized and further applied as a sorbent for chromium speciation in waters. Cr(III)-IIMs were prepared via solution blending method using blends of poly(vinyl alcohol) and sodium alginate as film-forming materials, poly(ethylene glycol) as a porogen agent, sodium alginate stabilized gold nanoparticles (SA-AuNPs) as a crosslinking and mechanically stabilizing component, and Cr(III) ions as a template species. The physicochemical characteristics of pre-synthesized AuNPs and obtained hydrogel membranes Cr(III)-IIM were studied by UV-vis and FTIR spectroscopy, TEM and SEM observations, N2 adsorption-desorption measurements, and XRD analysis. The mechanism of the adsorption process toward Cr(III) was best described by pseudo-first-order kinetic and Langmuir models. Experiments performed showed that quantitative retention of Cr(III) is attained in 20 h at pH 6 and temperature 40 °C. Under the same conditions, the adsorption of Cr(VI) is below 5%. A simple and sensitive analytical procedure was developed for the speciation of Cr in an aquatic environment using dispersive solid phase extraction of Cr(III) by Cr(III)-IIM prior to selective Cr(VI) measurement by ETAAS in the supernatants. The detection limits and reproducibility achieved for the Cr speciation analysis fulfill the requirements for their monitoring in waters under the demand of the Water Framework Directive.

The investigation of triadic silica-supported polyhexamethylene guanidine@nano-hydroxyapatite nanocomposites for Cr (VI) detection

Triadic silica-supported polyhexamethylene guanidine@nano-hydroxyapatite (HAP) composites were prepared and employed in a micro-column system for solid phase extraction of Cr (VI) with its determination by flame atomic absorption spectrometry (FAAS). It is found that the triadic silica-supported nano-HAP composites can efficiently adsorb Cr (VI) at pH 4.0–6.0, but absorb almost no Cr (III). The detection has a good linear range of 0.3–300 μg L−1, a detection limit of 0.09 μg L−1 (3σ, n = 11) and a precision of 1.3% (20 μg L−1, n = 11) on Cr (VI). The adsorption mechanisms are mainly electrostatic attraction and the channel effect. This method was successfully applied to the determination of chromium contents in cereal and water samples with recoveries of 99.5–109.8%.

Solid-phase extraction of Cr(VI) with magnetic melamine–formaldehyde resins, followed by its colorimetric sensing using gold nanoparticles modified with p-amino hippuric acid

A new method for magnetic solid-phase separation of trace-levels of Cr(VI) by using magnetic nanoparticles modified melamine–formaldehyde resin (Fe3O4@MFR) was described. Also, the selective and sensitive chemical optical probe was developed based on citrate-polyvinyl alcohol capped gold nanoparticle and modified with the reagent p-amino hippuric acid (PAH). Consequently, the optical probe was employed for the sensing of Cr(VI) ion in aqueous media. The sensing scheme is based on the complexation between PAH and reduced Cr(III). The linear calibration curve for Cr(VI) was calculated with preconcentration and was found in the range of 2.6–156 µg L−1 and the limits of detection for Cr(VI) were 10.4 µg L−1 and 2.0 µg L−1 with the naked eye and UV–vis spectroscopic detection, respectively. More importantly, both magnetic solid-phase extraction and colorimetric optical probe are selective for detection of the target analyte. The recoveries are between 96 and 99% when exercising 15 mg of the Fe3O4@MFR. The coupled approach was employed for the pre-concentration and quantification of Cr(VI) in two real water samples (tap water and mineral water) employing the standard addition protocol.

Derived N-doped carbon through core-shell structured metal-organic frameworks as a novel sorbent for dispersive solid phase extraction of Cr(III) and Pb(II) from water samples followed by quantitation through flame atomic absorption spectrometry

Highly porous carbon material is one of the most widely used sorbents in removing Cr and Pb from polluted water. Moreover, heavy metal ions of Pb(II) and Cr(III) have become the global health and environmental concerns. A novel nanoporous Zn/Co/C derived from ZIF-8/ZIF-67 core-shell was reported in the present study. The prepared sorbent was used for dispersive solid phase extraction of Cr(III) and Pb(II) ions. The extracted ions were then eluted by the aid of the acidic solution (HNO3) and analyzed via flame atomic absorption spectroscopy (FAAS). The prepared carbon materials were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), N2 adsorption-desorption and Fourier transform infrared spectroscopy (FT-IR). The characterization results indicated that the prepared porous carbon surface had functional groups such as -COOH, -OH, COC, etc. which can act as active sites during the adsorption process. The capacity of the sorbent ranged from 520 to 375 mg g−1. Under the optimum condition, the calculated limits of detections were 0.21 and 0.40 μg L−1 for Cr(III) and Pb(II) ions, respectively. The relative standard deviations (RSDs) were lower than 5.0%. The surface area and pore volume of the prepared sorbent were 128 m2 g−1 and 0.25 cm3, respectively. In addition, the effects of foreign ions on the extraction capability of the sorbent were also investigated. The results indicated that the vast majority of transition, alkaline, and earth alkaline metals do not interfere with environmentally relevant concentrations. The presented method was validated through analyzing standard reference material. Different types of real samples were analyzed in order to investigate the capability of the method for facile preconcentration of Cr and Pb ions.

A Cr(VI)-imprinted-poly(4-VP-co-EGDMA) sorbent prepared using precipitation polymerization and its application for selective adsorptive removal and solid phase extraction of Cr(VI) ions from electroplating industrial wastewater

A Cr(VI)-imprinted-poly(4-VP-co-EGDMA) (IIP) was proposed to be used in the process of selective extraction of low concentration of Cr(VI) ion from aqueous solution. The polymer was synthesized by using Cr(VI) ion as a template, 4-vinylphiridine (4-VP) as complexion agent and monomer, ethylene glycol dimethyl acrylate (EGDMA) as cross-linker, benzoyl peroxide (BPO) as initiator and ethanol/acetone as a porogen. Non ion-imprinted-poly(4-VP-co-EGDMA) (NIP) as a control polymer was prepared too. The synthesis was conducted by using precipitation polymerization method. The prepared of IIP unleached, IIP leached and NIP were characterized by XRD, FTIR, SEM-EDX and BET-BJH instrument. Based on the characterization data, it can be found that all of this imprinting material have a micro and mesopore structures. The effect of sorbent dosage, pH, contact time and temperature on Cr(VI) adsorption from aqueous solution were investigated. The result shows that the adsorption of Cr(VI) ion was highest at pH 2 with 30 min contact time at 313 K with an initial concentration of Cr(VI) 14 mg/L. The selective studies shows that the IIP material was a very selective to adsorp Cr(VI) even in water was found interfering ion such as Ni(II) and Cr(III) respectively. Kinetic and isotherm modeling were also studied by using 5 models in each. The result of modeling kinetic shows that Cr(VI) adsorption fit with the Pseudo-second-order model while modeling isotherm followed the Freundlich model. The application of this material to adsorb Cr(VI) from electroplating industrial waste which reaches 96% and the reusability testing also shows that this adsorbent has good stability even though it was used 10 times repeatedly.

Carbon-coated Fe3O4 nanoparticles with surface amido groups for magnetic solid phase extraction of Cr(III), Co(II), Cd(II), Zn(II) and Pb(II) prior to their quantitation by ICP-MS

A magnetic nanosorbent was prepared from Fe3O4 nanoparticles and polyacrylamide using a solvothermal process. Two functions are achieved simultaneously in this process: The first consists in the formation of a carbon layer around the Fe3O4 nanoparticles, and the second one in the functionalization with an amido group. This combination allows the protection of Fe3O4 nanoparticles from dissolution in acid medium during heavy metal adsorption. The adsorbent was characterized by SEM, TEM, EDS, FTIR, TGA, and in terms of surface area. Results showed the Fe3O4 nanoparticles to be embedded in a sheet of carbon with folded surfaces which is functionalized with amido groups. The nanosorbent was applied to the enrichment of Cr(III), Co(II), Cd(II), Zn(II) and Pb(II) via magnetic solid phase extraction (mag-SPE). The effects of pH value, eluent type and sample volume were optimized. The validation of the procedure was verified by the analysis of a wheat gluten certified reference material (8418). The limits of detection for the above ions range from 1 to 110 ng L−1. The relative standard deviations are <10%. The procedure was successfully applied to the enrichment of Cr(III), Co(II), Cd(II), Zn(II) and Pb(II) from various water and food samples.

Solid phase extraction method for the separation and determination of chromium(III) in the presence of chromium(VI) using silica gel modified by N,N′-bis-(α-methylsalicylidene)-2,2-dimethyl-1,3-propanediimine

N,N′-bis-(α-methylsalicylidene)-2,2-dimethyl-1,3-propanediimine (SBTD) modified silica gel was prepared and used as sorbent for solid phase extraction of Cr(III) ions from aqueous solution. This sorbent showed a high sorption affinity for Cr(III) while recovery of Cr(VI) was very low. The analyte ion retained on the column was eluted with 1 mol L −1 HNO 3. The chromium ion in the eluent was determined by graphite furnace atomic absorption spectrometry. The effects of different parameters such as pH, eluent type and volume, Schiff's base concentration, sample and eluent flow rate, interfering ions and adsorbent amount were investigated.

Removal of Toxic/Heavy Metal Ions Using Ion-Imprinted Aminofunctionalized Silica Gel

The investigation reports the preparation and evaluation of Cr(III) and Fe(III)-imprinted amino-functionalized silica gel adsorbents (APTS-Cr(III)-Si and APTS-Fe(III)-Si) for selective solid-phase extraction of Cr(III) and Fe(III), respectively, from aqueous solutions. The adsorbent materials were prepared by a surface imprinting technique using 3-aminopropyltrimethoxysilane as the surface modifying ligand. The effects of solution pH, sorption time, temperature, and initial metal ion concentration upon adsorption characteristics were investigated. The adsorption isotherms for Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) were evaluated and the thermodynamics of the adsorption processes were correlated. By optimizing the parameters, the synthesized materials could be used successfully for selective removal of trivalent cations from a mixture of cations in dilute aqueous solution.