Surface molecularly imprinted amino-functionalized alginate microspheres for enantio-selective extraction of l-ascorbic acid.

A surface molecular imprinting technique was utilized in the fabrication of an enantio-selective adsorbent based on amino-functionalized alginate microspheres for chiral resolution of ascorbic acid. Alginate microspheres were first strengthened via epichlorohydrin (ECH) covalent cross-linking then functionalized with amino groups through graft copolymerization of polyacrylamide (PAm) followed by Hofmann degradation. Surface molecular imprinting was then performed under mild conditions by ionic interaction between the surface incorporated amine groups and the template l-ascorbic acid enantiomers followed by cross-linking with glyoxal. l-Ascorbic acid enantio-selective adsorbent (LA-Alg) was finally obtained by removing the template molecules out of the cross-linked network formed on the surface of the modified alginate particles. The synthetic steps were monitored using elemental analysis and FTIR spectra. Also, the surface morphologies of the native unmodified alginate along with both imprinted and non-imprinted adsorbent particles were examined by SEM. Moreover, the crystalline profile and thermal properties of both native and modified samples were investigated using XRD spectra and thermogravimetric analysis (TGA), respectively. The effect of pH on the extraction process was studied and indicated that the maximum adsorption was obtained at pH 4. Also, adsorption isotherms over LA-Alg adsorbent displayed the best fit with Langmuir model with maximum adsorption capacity 116 ±â€¯1 and 67 ±â€¯1 mg/g with respect to both l- and d-ascorbic acid, respectively. Moreover, the chiral resolution experiment using batch technique indicated 72% enantiomeric excess.

Preparation of ruthenium (III) ion-imprinted beads based on 2-pyridylthiourea modified chitosan.

Ru(III) ion-imprinted bio-adsorbent based on 2-pyridylthiourea modified chitosan (Ru-PTCS) had been manufactured, investigated and employed for selective extraction of Ru(III) ions from aqueous medium containing interfering metal ions that maybe coexist and compete with Ru(III) ions. Elemental analysis, FTIR and NMR techniques were performed to characterize the chemical structure of the synthesized polymeric materials. The optimum extraction conditions, selectivity and regeneration efficiency were evaluated via batch experiments. The maximum adsorption was obtained at pH 4, and the extraction kinetics followed the pseudo-second order model. Also, the equilibrium isotherms were in accordance with Langmuir model and the maximum adsorption capacity was 249 ±â€¯1 mg/g. The prepared Ru-PTCS exhibited a high affinity toward the targeted Ru(III) ions even in multi-ionic media containing other similar competitive metal ions. In addition, the polymeric selective bio-adsorbent maintained about 96% of its efficiency after 8 adsorption/desorption cycles.

Fabrication of Au(III) ion-imprinted polymer based on thiol-modified chitosan.

Au(III) ions were selectively extracted from aqueous media using Au(III) ion-imprinted bio-adsorbent based on modified chitosan (Au-CMB). First, 2-mercaptobenzaldehyde-chitosan Schiff base was prepared and interacted with Au(III) ions. The obtained polymeric Au(III) complex was then cross-linked by epichlorohydrin (ECH) before leaching the template Au(III) ions out of the cross-linked matrix. During the synthetic procedures, the obtained chitosan derivatives were characterized by Elemental analysis, FTIR and NMR spectra. Moreover, the crystalline structures along with surface morphology of the fabricated polymeric materials were investigated using X-ray diffraction (XRD) spectra and scanning electron microscope (SEM), respectively. The Au(III) ions uptake studies indicated that the adsorption process was greatly influenced by pH and followed the pseudo-second-order kinetic mechanism. Furthermore, the adsorption was endothermic and the isotherms showed the best fit with Langmuir model with qm 370±0.5 and 195±0.5mgg-1 in case of Au-CMB and NI-CMB, respectively.

Ion-imprinted modified chitosan resin for selective removal of Pd(II) ions.

In this work, a selective Pd(II) ions chelating resin based on 2-aminobenzaldehyde modified chitosan Schiff's base (Pd-CAZ) was synthesized through ion-imprinting technique. All the performed chemical and morphological changes during the modification and Pd(II) ion-imprinting process were investigated using instrumental techniques including FTIR, (1)H NMR, XRD and SEM. In addition, the mechanism of Pd(II) binding to the synthesized polymeric active sites was elucidated using both XPS and FTIR spectra, and the results indicated that Pd(II) ions coordinated in square planar geometry. Also, the selective extraction experiments with respect to Pd-CAZ and control non-imprinted NI-CAZ resins were performed to obtain the fundamental thermodynamic, kinetic and isotherm parameters. In all cases the adsorption was endothermic, spontaneous, fit well with pseudo-second order kinetic model and Langmuir adsorption isotherm model with maximum adsorption capacities of 275±0.4 and 114±0.2 mg/g for Pd-CAZ and NI-CAZ, respectively. Moreover, the regeneration and recovery experiments indicated that the resin maintain about 96% of its original activity after the fifth adsorption-desorption cycle, revealing the high economic value.

Synthesis and characterization of ion-imprinted resin for selective removal of UO2 (II) ions from aqueous medium.

In this work, uranyl ion-imprinted resin based on 2-(((4-hydroxyphenyl)amino)methyl)phenol was synthesized by condensation polymerization of its uranyl complex in presence of resorcinol and formaldehyde cross-linkers. Numerous instrumental techniques including elemental analysis, Fourier transform infrared spectroscopy, ultraviolet, (1) H along with (13) C nuclear magnetic resonance spectroscopy have been employed for complete characterization of the synthesized ligand and its uranyl complex. Additionally, the obtained ion-imprinted and non-imprinted resins were investigated using scanning electron microscope and Fourier transform infrared spectroscopy. The effects of various essential parameters such as pH, temperature and contact time on removal of uranyl ions have been examined, and the results indicated that the obtained resin exhibited the optimum activity at pH 5. Furthermore, the adsorption process was spontaneous at all studied temperatures and followed the second-order kinetics model. Also, Langmuir adsorption isotherm exhibited the best fit with the experimental results with maximum adsorption capacity 139.3 mg/g. Moreover, the selectivity studies revealed that the ion-imprinted resin exhibited an obvious affinity toward the uranyl ions in presence of other metal ions compared with the non-imprinted resin.

Preparation of L-tryptophan imprinted microspheres based on carboxylic acid functionalized polystyrene.

In this work, polymerizable (4-vinylbenzoyl)-L-tryptophan (VBLT) was synthesized and characterized utilizing, elemental analysis, mass spectra, FTIR, (1)H and (13)CNMR. VBLT was then copolymerized with styrene and divinylbenzene cross-linker using potassium persulfate free radical initiator. The template L-Trp molecules were then leached out from the cross-linked network leaving selective recognition cavities, which are able to selectively rebind with L-Trp than D-Trp. The obtained molecularly imprinted LT-CPS resin was examined using various instrumental techniques such as SEM and FTIR to be then employed in a series of adsorption experiments to evaluate the essential parameters for efficient selective extraction of L-Trp. The kinetics of adsorption displayed the best fit with pseudo-second-order kinetic model, suggesting chemical sorption as the rate determining step. Additionally, the most effective interpretation of the adsorption isotherm data was acquired by Langmuir isotherm, and the maximum adsorption capacities were 155±2 and 82±1 mg/g for L- and D-Trp, respectively. Moreover, chiral resolution of L, D-Trp racemic mixture was performed using column of LT-CPS.

Synthesis and characterization of uranyl ion-imprinted microspheres based on amidoximated modified alginate.

Surface ion-imprinting technique was utilized for the preparation of surface ion-imprinted chelating microspheres based on amidoximated modified alginate (U-AOX) in presence of uranyl ions as a template and glutaraldehyde cross-linker. Different instrumental techniques such as elemental analysis, scanning electron microscope (SEM), FTIR, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction spectra were employed for full investigation of the manufactured materials. The synthesized microspheres displayed a higher ability for selective extraction of UO2(2+) when compared to the non-imprinted microspheres (NI-AOX). In addition, the essential parameters such as pH, temperature, time and initial uranyl ion concentration were evaluated in order to optimize the conditions of the adsorption process. The results indicated that pH 5 was the best for the UO2(2+) removal, also, the adsorption was endothermic in nature, follows the second-order kinetics and the adsorption isotherm showed the best fit with Langmuir model with maximum adsorption capacity of 155 ± 1 and 64 ± 1 mg/g for both U-AOX and NI-AOX respectively. Desorption and regeneration had been carried out using 0.5M HNO3 solution and the results indicated that the microspheres maintained about 96% of its original efficiency after five consecutive adsorption-desorption cycles.

Synthesis and characterization of ion-imprinted resin based on carboxymethyl cellulose for selective removal of UO2²âº.

In this work, the surface ion-imprinting technique was employed for the preparation of surface ion-imprinted chelating microspheres resin based on modified salicylaldehyde-carboxymethyl cellulose (U-CMC-SAL) in presence of uranyl ions as a template and formaldehyde as a cross-linker. Various instrumental techniques such as elemental analysis, scanning electron microscope (SEM), FTIR and X-ray diffraction spectra were utilized for full characterization of the prepared polymeric samples. The prepared resin exhibited a higher capability for selective removal of UO2²âº when compared to the non-imprinted resin (N-CMC-SAL). Also, different important parameters such as pH, temperature, time and initial metal ion concentration were examined in order to evaluate the optimum condition for the adsorption process. The results indicated that pH 5 was the best for the UO2²âº uptake, in addition, the adsorption was exothermic in nature, follows the second-order kinetics and the adsorption isotherm showed the best fit with Langmuir isotherm model with maximum adsorption capacity of 180 ± 1 and 97 ± 1 mg/g for both U-CMC-SAL and N-CMC-SAL respectively. Desorption and regeneration were carried out using 0.5M HNO3 solution and the results confirmed that the resin keeps about 92% of its original efficiency after five consecutive adsorption-desorption operations.

Modification and characterization of PET fibers for fast removal of Hg(II), Cu(II) and Co(II) metal ions from aqueous solutions.

A new chelating fiber (PET-TSC) was prepared with PET for fast removal of Hg(2+), Cu(2+) and Co(2+) from water. Elemental analysis, SEM, BET surface area, (13)C NMR, FTIR and X-ray diffraction spectra were used to characterize PET-TSC. The higher uptake capacity of the studied metal ions was observed at higher pH values. Kinetic study indicated that the adsorption of Hg(2+), Cu(2+) and Co(2+) followed the pseudo-second-order equation, suggesting chemical sorption as the rate-limiting step of the adsorption process. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities were 120.02, 96.81 and 78.08 mg/g for Hg(2+), Cu(2+) and Co(2+) ions, respectively. 1M HCl or 0.1M EDTA could be used as effective eluant to desorb the Hg(2+), Cu(2+) and Co(2+) adsorbed by PET-TSC, and the adsorption capacity of PET-TSC for the three heavy metal ions could still be maintained at about 90% level at the 5th cycle. Accordingly, it is expected that PET-TSC could be used as a promising adsorbent for fast removal of heavy metal ions from water, and the present work also might provide a simple and effective method to reuse the waste PET fibers.

Adsorption of Cu(II), Cd(II) and Ni(II) ions by cross-linked magnetic chitosan-2-aminopyridine glyoxal Schiff's base.

The adsorption of Cu(II), Cd(II) and Ni(II) ions from aqueous solution by cross-linked magnetic chitosan-2-aminopyridine glyoxal Schiff's base resin (CSAP) was studied in a batch adsorption system. Cu(II), Cd(II) and Ni(II) removal is pH dependent and the optimum adsorption was observed at pH 5.0. The adsorption was fast with estimated initial rate of 2.7, 2.4 and 1.4 mg/(g min) for Cu(2+), Cd(2+) and Ni(2+) respectively. The adsorption data could be well interpreted by the Langmuir, Freundlich and Temkin model. The maximum adsorption capacities obtained from the Langmuir model were 124±1, 84±2 and 67±2 mg g(-1) for Cu(2+), Cd(2+) and Ni(2+) respectively. The adsorption process could be described by pseudo-second-order kinetic model. Thermodynamic parameters revealed the feasibility, spontaneity and exothermic nature of adsorption. The sorbents were successfully regenerated using EDTA and HCl solutions.

Preparation of cross-linked magnetic chitosan-phenylthiourea resin for adsorption of Hg(II), Cd(II) and Zn(II) ions from aqueous solutions.

In this study, cross-linked magnetic chitosan-phenylthiourea (CSTU) resin were prepared and characterized by means of FTIR, (1)H NMR, SEM high-angle X-ray diffraction (XRD), magnetic properties and thermogravimetric analysis (TGA). The prepared resin were used to investigate the adsorption properties of Hg(II), Cd(II) and Zn(II) metal ions in an aqueous solution. The extent of adsorption was investigated as a function of pH and the metal ion removal reached maximum at pH 5.0. Also, the kinetic and thermodynamic parameters of the adsorption process were estimated. These data indicated that the adsorption process is exothermic and followed the pseudo-second-order kinetics. Equilibrium studies showed that the data of Hg(II), Cd(II) and Zn(II) adsorption followed the Langmuir model. The maximum adsorption capacities for Hg(II), Cd(II) and Zn(II) were estimated to be 135 ± 3, 120 ± 1 and 52 ± 1 mg/g, which demonstrated the high adsorption efficiency of CSTU toward the studied metal ions.

Preparation and characterization of chitosan-grafted-poly(2-amino-4,5-pentamethylene-thiophene-3-carboxylic acid N'-acryloyl-hydrazide) chelating resin for removal of Cu(II), Co(II) and Ni(II) metal ions from aqueous solutions.

The graft copolymerization of ethylacrylate (EA) onto chitosan initiated by potassium persulphate and Mohr's salt combined redox initiator system in limited aqueous medium was carried out in heterogeneous media. Moreover, modification of the grafted chitosan was carried out by reaction of the ester group (-COOEt) with 2-amino-4,5-pentamethylene-thiophene-3-carboxylic acid hydrazide which eventually produce chitosan-grafted-poly(2-amino-4,5-pentamethylene-thiophene-3-carboxylic acid N'-acryloyl-hydrazide) (chitosan-g-ATAH) chelating resin. The application of the modified resin for metal ion uptake was studied using Cu(2+), Co(2+) and Ni(2+) ions. The modified chelating resins were characterized using FTIR spectroscopy, SEM and X-ray diffraction.

Preparation and characterization of chelating fibers based on natural wool for removal of Hg(II), Cu(II) and Co(II) metal ions from aqueous solutions.

The graft copolymerization of acrylonitrile (AN) onto natural wool fibers initiated by KMnO(4) and oxalic acid combined redox initiator system in limited aqueous medium was carried out in heterogeneous media. Moreover, modification of the grafted wool fibers was done by changing the nitrile group (-CN) into cyano-acetic acid α-amino-acrylic-hydrazide through the reaction with hydrazine hydrate followed by ethylcyanoacetate which eventually produce wool-grafted-poly(cyano-acetic acid α-amino-acrylic-hydrazide) (wool-g-PCAH) chelating fibers. The application of the modified fibers for metal ion uptake was studied using Hg(2+), Cu(2+) and Co(2+). The modified chelating fibers were characterized using FTIR spectroscopy, SEM and X-ray diffraction.