Search

Astilbin (AST), isoastilbin (ISO), and engeletin (ENG) are the main flavonoids in Rhizoma Smilacis Glabrae (RSG) and have many biological activities. In this study, the adsorption kinetics of AST, ISO, and ENG on HPD-300 resin was investigated and their adsorption processes conformed to a pseudo-second-order kinetics equation. The fitting curves of the intraparticle diffusion model showed three linear stages and did not pass through the origin, meaning the adsorption process of the three flavonoids was controlled by boundary layer diffusion and intraparticle diffusion. Their adsorption isotherms were also constructed and could be well-fitted by the Langmuir equation. A low temperature was favorable for their adsorption. The relative adsorption capacity of ENG was significantly higher than those of the other two compounds, indicating that the substitution pattern on ring B has an important impact on the adsorption of flavonoids with resin. The separation process was optimized by dynamic adsorption/desorption experiments. After separation, the purities of AST, ISO, and ENG increased from 5.55%, 1.22%, and 0.45% to 27.46%, 6.14%, and 2.27%, respectively, and all the recoveries exceeded 75%. After that, the three compounds were further separated by preparative HPLC and silica gel chromatography. In the final product, the purities of AST, ISO, and ENG could reach above 98%. [ABSTRACT FROM AUTHOR]

Crosslinked polyacrylonitrile (PAN) was synthesized with divinylbenzene as the crosslinker with an iron(III)-mediated atom transfer radical polymerization method with activators regenerated by electron transfer. The polymerization exhibited first-order kinetics with respect to the polymerization time. Hydroxylamine hydrochloride (NH2OH·HCl) was used to modify the cyano groups of the crosslinked PAN to obtain amidoxime (AO) groups. The AO-crosslinked PAN was used to remove Hg(II). The optimum pH, adsorption kinetics, and adsorption isotherms were investigated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Porous a crylonitrile (AN)/methyl acrylate (MA) copolymer beads were synthesized by suspended emulsion polymerization and amidoximated for the purpose of Ag+ adsorption. Optimum amidoximation temperature and time were determined by following the adsorption capacity for Ag+. The results showed that amidoximated AN/MA (AO AN/MA) with the amidoximation temperature 70°C and amidoximation time 20 hr had a relatively higher adsorption capacity for Ag+. The effect of pH on adsorption for Ag+ was studied; the highest adsorption capacity presented at pH 5.0. Adsorption kinetics and isotherms of AO AN/MA copolymer beads for Ag+ were also investigated. The kinetics data indicated that the adsorption process was governed by the film diffusion and followed both pseudo-first-order and pseudo-second-order rate model. The isotherms indicated that adsorption capacities increased with equilibrium concentration and temperature. The Langmuir model and Sips model could describe the isothermal process. Thermodynamic analysis revealed that the adsorption behaviors of Ag+ ions on AO AN/MA could be considered as endothermic and physical sorption process. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The article examines the adsorption properties of macroporous chelating resins incorporating heterocyclic functional groups via hydrophilic poly(ethylene oxide) spacer arms. Results found the resins' high affinity for Hg2+ and Ag+. The relationship of hydrophilic spacer arms introduced between the polymeric matrix and heterocyclic functional groups and the hydrophilicity capacity of the resins are noted. The increase in the adsorption capacities for metal ions is cited.

The article discusses a study of the adsorption for metal ions of Schiff base-type chitosan coated cotton fiber (SCCH). Yuhuan Halobios Co. of China has provided the chitosan with degree of deacetylation 90%. Results indicate the presence of competition adsorption between copper (Cu)2+ and hydrogen (H)+ for adsorption sites. Liquid film diffusion was used to control the adsorption for nickel (Ni)2+, lead (Pb)2+ and cadmium (Cd)2+.

Abstract: Differences between adsorption properties for Hg(II) and Au(III) on polystyrene-supported bis-8-oxyquinoline-terminated open-chain crown ether (PS-DB) were studied by scanning electron microscope (SEM), X-ray diffraction (XRD) and the density functional theory (DFT) method. The comparison studies included kinetics, equilibriums and thermodynamics of the adsorption process. Pseudo-first-order and pseudo-second-order kinetic models were applied to test the experimental data. The pseudo-second-order kinetic model provided a better correlation with the experimental data for Hg(II) in comparison with the pseudo-first-order model. While for Au(III), the conclusion was the reverse. Both the adsorption rate and adsorption amount at equilibrium for Hg(II) were greater than those for Au(III) ions, which was probably caused by the differences in form and volume between the two kinds of absorbed ions. Langmuir, Freundlich and Tempkin isotherm models were applied in the adsorption isotherm study. The results showed that the Langmuir and Tempkin isotherm models were more applicable in describing the processes. The thermodynamic parameters for the adsorption process such as free energy of adsorption (ΔG), enthalpy of adsorption (ΔH) and entropy of adsorption (ΔS) were calculated. The density functional theory (DFT) method was used to investigate the coordination geometries and the interactions between the metal ions with PS-DB. These results showed that the adsorption for Hg(II) was physisorption while that for Au(III) was chemisorption, which was also consistent with the data obtained from the Dubinin–Radushkevich (D–R) isotherm model and ΔH values. [Copyright &y& Elsevier]

Abstract: In order to explore the reuse properties of oxidized chelating resin containing sulfur after adsorption, two kinds of novel chelating resins, poly[4-vinylbenzyl-(2-hydroxyethyl)] sulfoxide (PVBSO) and poly[4-vinylbenzyl-(2-hydroxyethyl)] sulfone (PVBSO2), were synthesized using poly[4-vinylbenzyl-(2-hydroxyethyl)] sulfide (PVBS) as material. Their structures were confirmed by FTIR and XPS. The adsorption properties and mechanism for metal ions such as Au3+, Pt4+, Pd2+, Hg2+, Cu2+, Ni2+, Fe3+, Pb2+, Cd2+, and Zn2+ were investigated. Experimental results showed that PVBSO had good adsorption and selective properties for Au3+, Pd2+ and Cu2+ when the coexisting ion was Pt4+, Ni2+, Pb2+ or Cd2+. In the aqueous system containing Cu2+ and Pb2+ or Cu2+ and Cd2+, PVBSO2 only adsorbed Cu2+. The selective coefficients of PVBSO and PVBSO2 were α Au/Pt =4.8, α Au/Pd =11.8, α Pd/Pt =10.9, α Cu/Ni =2.5, α Cu/Cd =41.2, α Cu/Pb =∞, α Cu/Ni =3.0, α Cu/Cd =∞, α Cu/Pb =∞, respectively. [Copyright &y& Elsevier]

Vitexin-4″- O -glucoside and vitexin-2″- O -rhamnoside are the major flavonoids of hawthorn leaves. In this work, the adsorption and desorption characteristics of vitexin-4″- O -glucoside and vitexin-2″- O -rhamnoside on seven macroporous resins were evaluated. Among the tested resins, the HPD-400 resin showed the best adsorption and desorption capacities. Adsorption isotherms were constructed for the HPD-400 resin and well fitted to Langmuir and Freundlich models. Dynamic adsorption and desorption tests were performed on column packed with the HPD-400 resin to optimize the chromatographic parameters. After one run treatment with the HPD-400 resin, the contents of vitexin-4″- O -glucoside and vitexin-2″- O -rhamnoside in the product were increased 8.44-fold and 8.43-fold from 0.720% and 2.63% to 6.08% and 22.2% with recovery yields of 79.1% and 81.2%, respectively. These results show that the developed method is a promising basis for the large-scale purification of vitexin-4″- O -glucoside and vitexin-2″- O -rhamnoside from hawthorn leaves and other plant materials. [ABSTRACT FROM AUTHOR]

Abstract: Two types of silica gel supported amidoxime (SG-HE-AO and SG-HO-AO) adsorbents were prepared via the reactions of silica gel supported acrylonitrile functional group (SG-AN) with hydroxylamine under alkaline conditions. The SG-AN was obtained by so-called “heterogeneous” and “homogeneous” methods and named SG-HE-AN and SG-HO-AN, respectively. All the structures of adsorbents and intermediate were characterized by FT-IR, SEM, porous structure analysis and elemental analysis. The amidoxime group content of SG-HE-AO and SG-HO-AO were 1.28 and 0.77mmolg−1, respectively, indicating that the heterogeneous method is more effective than the homogeneous method to anchored functional groups onto the surface of silica gel in this study. In terms of Hg(II) adsorption, SG-HE-AO exhibited better capability than SG-HO-AO. The adsorption kinetics of the two adsorbents followed the pseudo second-order process in the temperature range of 5–35°C. Increased temperature was beneficial to adsorption. Langmuir and Freundlich isotherm models were both applied to experimental data analysis, and the former proved to be a better fit. Finally, in Hg(II)–Pb(II), Hg(II)–Ag(I), Hg(II)–Cu(II) and Hg(II)–Ni(II) binary systems, both SG-HE-AO and SG-HO-AO exhibited excellent adsorption selectivity for Hg(II). [Copyright &y& Elsevier]

Abstract: The adsorption kinetics and equilibrium of silica-gel functionalized with amino-terminated dendrimer-like polyamidoamine (PAMAM) polymers SiO2-G1.0, SiO2-G2.0 and SiO2-G3.0 for Cu2+ in ethanol fuel were investigated by using batch method. The results indicated that the all the adsorptions of the three adsorbents followed well the pseudo second-order model. The adsorption isotherms were fitted by Langmuir model, Freundlich model and Dubinin–Radushkevich (D–R) model. The results showed that Langmuir model was more suitable to describe the equilibrium data than the Freundlich model. From the D–R isotherm model, the mean free energy E calculated of the three adsorbents showed that the adsorptions were taken place by physical processes. Thermodynamic parameters, ΔG 0, ΔH 0 and ΔS 0 indicated the Cu2+ adsorption to be endothermic and spontaneous with decreased randomness at the solid-solution interface, resulting in their higher adsorption capacities at higher temperature. The effect of generation number of PAMAM polymers loaded on silica-gel, contact time, initial concentration and temperatures on the adsorption capabilities were studied in detail. Moreover, the adsorption mechanism of copper from ethanol fuel was also presumed. [Copyright &y& Elsevier]

Abstract: Using waste poly(p-phenylene terephthalamide) fibers (PPTA) as a starting material and novel Schiff base-containing adsorbent for metal ions, PPTA-Sal and its basification product PPTA-Sal(Na) were prepared via a series of chemical modification reactions. The structures of the modified fibers were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TG). Metal ions, such as Pb2+, Cu2+ and Ni2+, were chosen as representatives to determine the adsorption capacities of the modified fibers in aqueous solutions. The experimental results showed that the adsorption capacities for Pb2+ of PPTA-Sal and PPTA-Sal(Na) can reach 15.12 and 19.06mg/g respectively, which are much higher than the 10.56mg/g of the intermediate product amination PPTA (PPTA-NH2). The adsorption of Pb2+ on PPTA-Sal and PPTA-Sa(Na) followed well the pseudo second-order model. Langmuir and Freundlich models were employed to fit the isotherm adsorption of Pb2+ on PPTA-Sal and PPTA-Sal(Na), and the results revealed that both models were able to closely predict the experimental data. The Freundlich isotherm was slightly better than the Langmuir isotherm in describing the Pb2+ adsorption onto PPTA-Sal(Na), while the latter model was more suitable for fitting the data of Pb2+ adsorption onto PPTA-Sal. The adsorption capacities of PPTA-Sal and PPTA-Sal(Na) were compared using various adsorbents. [Copyright &y& Elsevier]

Abstract: A novel method of surface modification was developed via iron (III)-mediated atom transfer radical polymerization, with activators regenerated by electron transfer (ARGET ATRP) on the surfaces of polystyrene resin-supported N-chlorosulfonamide groups. The well-defined polyacrylonitrile (PAN) was grafted onto the surfaces of the polystyrene (PS). The graft reaction exhibited first-order kinetics with respect to the polymerization time in the low-monomer-conversion stage. The cyano group of PAN-g-PS was modified by NH2OH·HCl to yield amidoxime (AO) groups. The AO groups had been demonstrated to be an efficient Hg-specific sorbent, which can remove Hg2+ from solutions. No interference arose from common metal ions, such as Pd2+, Ag+, and Cu2+. Three adsorption–desorption cycles demonstrated that this resin is suitable for reuse without any considerable change in adsorption capacity. [Copyright &y& Elsevier]

Abstract: The adsorption behaviors of Hg(II) on adsorbents, chitosan functionalized by generation 1.0–3.0 of amino-terminated hyperbranched polyamidoamine polymers (denoted as CTS-1.0, CTS-2.0 and CTS-3.0, respectively), were studied. The optimum pH corresponding to the maximum adsorption capacities was found to be 5.0 for the three adsorbents. The experimental equilibrium data of Hg(II) on the three adsorbents were fitted to the Freundlich and the Langmuir models, and it is found that the Langmuir isotherm was the best fitting model to describe the equilibrium adsorption. The kinetics data indicated that the adsorption process of Hg(II) ions on CTS-1.0, CTS-2.0 and CTS-3.0 were governed by the film diffusion and followed pseudo-second-order rate model. Thermodynamic analysis and FTIR analysis revealed that the adsorption behaviors of Hg(II) ions on the three adsorbents could be considered as spontaneous, endothermic and chemical sorption process, resulting in their higher adsorption capacities at higher temperature. [Copyright &y& Elsevier]

Two types of chitosan-coated cotton fibers (SCCH and RCCH) were applied to remove and recover Hg(II) ions in aqueous solution. The adsorption kinetics and isotherms of the two fibers for Hg(II) were investigated at different temperatures. The results revealed that the adsorption kinetic processes of SCCH and RCCH fibers for Hg(II) followed the pseudo second-order model at lower temperatures and the pseudo first-order model at higher temperatures. Both the Langmuir and Freundlich models well described the adsorption isotherms of SCCH and RCCH fibers for Hg(II) in the temperature range studied. SCCH and RCCH fibers selectively adsorbed Hg(II) from binary ion systems in the presence of Pb(II), Cu(II), Ni(II), Cd(II), Zn(II), Co(II), Mn(II) and Ag(I). Increased temperature was beneficial to adsorption. The recovery of Hg(II) from aqueous solutions was also studied as a function of sample flow rate and volume, concentration and volume of eluent, elution rate, quantity of adsorbents added and concomitant ions. The results showed that the two fibers efficiently enriched and recovered Hg(II) in the presence of alkali and alkaline earth metals and some heavy metals under optimum conditions. The RCCH fiber exhibited better stability than the SCCH fiber following repeated use. [Copyright &y& Elsevier]

Four kinds of silica-gel (SG)-supported diethylenetriamine (DETA) chelating resins SG-DETA-1, SG-DETA-2, SG-DETA-3, and SG-DETA-4 were prepared by functionalization of silica-gel via so-called “heterogeneous-direct-amination” (hetero-DA), “homogeneous-direct-amination” (homo-DA), “heterogeneous end-group protection” (hetero-EGP), and “homogeneous end-group protection” (homo-EGP) routes, respectively. These functionalized reactions on silica-gel were confirmed through elemental analysis, infrared spectroscopy, X-ray diffractometry, porous analysis, and thermogravimetry. Element analysis revealed that the direct-amination routes and homogeneous condition were more beneficial than the corresponding end-group protection routes and heterogeneous condition to the syntheses of chelating resins with high N content. Several metal ions, such as Ag+, Cu2+, Ni2+, Hg2+, Zn2+ and Pb2+, were chosen as representatives to investigate the relationship between adsorption capacities and N content of ligands onto the surface of silica-gel. The experiments results showed that all resins, SG-DETA-1, SG-DETA-2, SG-DETA-3 and SG-DETA-4, had a better adsorption for Hg2+ and Cu2+ than others. One conclusion should be drawn from the above compared experiments, that is, higher N content of silica-gel resins does not ensure a higher utilization ratio of N. [Copyright &y& Elsevier]

Abstract: Four kinds of silica-gel supported diethylenetriamine adsorbents with different structures, were prepared by so-called “heterogeneous-direct-amination” (hetero-DA), “homogeneous-direct-amination” (homo-DA), “heterogeneous end-group protection” (hetero-EGP), and “homogeneous end-group protection” (homo-EGP) methods, respectively. The obtained products were named SG-HE-dD, SG-HO-dD, SG-HE-pD and SG-HO-pD, respectively (where SG means silica-gel; HE means heterogeneous, HO means homogeneous, d means direct, p means protected and D means diethylenetriamine). Their structures were characterized by FT-IR, elemental analysis, porous structure analysis and thermogravimetric analysis. The adsorption capabilities of such adsorbents towards Hg(II) were studied and evaluated by static method. SG-HE-pD and SG-HO-pD showed higher performance towards Hg(II) adsorption than corresponding counterparts SG-HE-dD and SG-HO-dD, even though the former two possessed lower contents of diethylenetriamine (DETA). The kinetics data indicated that the adsorption process was governed by the film diffusion and followed pseudo-first-order rate model for SG-HE-dD, SG-HO-dD and SG-HE-pD and pseudo-second-order model for SG-HO-pD. The Langmuir model was applied to fit the experimental equilibrium data for all adsorbents. The end-group protection method exhibited its advantage in preparation of effective adsorbent for metal ions uptake compared to the direct-amination method. [Copyright &y& Elsevier]

Abstract: Two novel chelating resins were prepared by anchoring ethylenediamine to crosslinked polystyrene via a spacer containing sulfide. Their structures were characterized by Fourier transform-infrared spectra (FTIR) and scanning electron microscopy (SEM). Porous structure parameters of the resins were measured by ASAP 2020 using BET and BJH methods. Their adsorption capacities for several heavy metal ions especially Hg2+ were investigated. The results showed that for the two resins, the more N contents did not mean the better adsorption capacity and the saturated adsorption capacity of poly(2-ethylenediamidomercaptomethylstyrene) (PSM-EDA) for Hg2+ could reach to 3.0mmol/g at room temperature. Isothermal adsorptions of the resins for Hg2+ could be described by Langmuir formula. The adsorption mechanism of the resins for Hg2+, Cu2+ and Ag+ was confirmed by X-ray photoelectron spectroscopy (XPS) and FTIR. [Copyright &y& Elsevier]

Abstract: Two novel chelating resins, polystyrene supported G1.0 diethanolamine-typed dendrimer (PS-DEA) and G2.0 diethanolamine-typed dendrimer (PS-(DEA)2), were prepared by anchoring low-generations diethanolamine-typed dendrimer into crosslinked polystyrene in this paper. Fourier transform-infrared spectra (FTIR), scanning electron microscopy (SEM) and elemental analysis were employed to character their structures. The results of adsorption for metal ions showed that the resins had good adsorption capacities for Cu2+, Ag+ and Hg2+, especially PS-DEA for Cu2+. The adsorption kinetics and adsorption isotherms of PS-DEA for Cu2+ and PS-(DEA)2 for Hg2+ were studied. The results showed that the adsorption kinetics of the two resins can be modeled by pseudo second-order rate equation wonderfully and Langmuir and Freundlich equations could well interpret the adsorption of PS-(DEA)2 for Hg2+ and PS-DEA for Cu2+, respectively. The adsorption mechanism of the resins for Cu2+ was confirmed by X-ray photoelectron spectroscopy (XPS). [Copyright &y& Elsevier]

Abstract: A novel chelating resin containing S, N and O atoms (PSME–EDA) was synthesized by using poly(2-hydroxyethylmercaptomethylstyrene) (PSME) and diethanolamine (EDA) as materials. Its structure was characterized by elemental analysis, Fourier transform-infrared spectra (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The adsorption of the resin for Hg2+ was investigated. The saturated adsorption capacity of PSME–EDA for Hg2+ could reach to about 1.1mmol/g at 25°C when the initial Hg2+ concentration was 0.02mol/l. Some factors affecting the adsorption such as temperature, reaction time and ion concentration were also studied. The results showed that adsorption was controlled by liquid film diffusion. The increasing of temperature was beneficial to adsorption. The Langmuir model was better than the Freundlich model to describe the isothermal process. The values of ΔG, ΔH, and ΔS calculated at 25°C were −7.99kJmol−1, 22.5kJmol−1 and 34.4Jmol−1 K−1, respectively. The adsorption mechanism of PSME–EDA resin for Hg(II) was confirmed by X-ray photoelectron spectroscopy (XPS). [Copyright &y& Elsevier]