首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 676 毫秒
1.
Summary Sorption of hexavalent chromium ions from aqueous solution by 4- vinyl pyridine (4-VP) grafted poly(ethylene terephthalate) (PET) fibers was studied. The Influences of adsorption time, pH of solution and Cr(VI) concentration on the adsorbed amount were investigated. 30 minutes of treatment time was found to be sufficient to reach equilibrium. pH 3.0 was found as the optimum pH value in the process. The maximum adsorption capacity of the material (ks) was found to be 263.16 mg g-1. It was found that the reactive fibers are stable and regenerable by acid or base without losing their activity.  相似文献   

2.
“Devil tree saw dust”; a novel biosorbent has been utilised successfully for the removal of hexavalent chromium from contaminated water. Batch adsorption procedure is utilised to test the ability of saw dust as an adsorbent for hexavalent chromium (reduction coupled adsorption). The contribution of various parameters on sorption, such as contact time, sorbate concentration, pH of the medium and temperature were estimated and maximum uptake of hexavalent chromium from contaminated water was 333.33 mg g?1 at pH 2.0 and temperature of 35°C. Hexavalent chromium uptake from contaminated water followed the pseudo‐first‐order rate expression. The standard free energy change (ΔG0), standard enthalpy change (ΔH0) and standard entropy change (ΔS0) have also been evaluated and it has been concluded that the sorption was feasible, spontaneous and endothermic in nature. The process follows well Langmuir isotherm. Fourier Transform Infra‐Red (FTIR) spectroscopy and scanning electron microscopy (SEM) of hexavalent chromium loaded and unloaded saw dust were performed, SEM clearly indicates chromium adsorption. FTIR spectroscopy revealed the involvement of carbonyl, hydroxyl and amide groups on the cell surfaces in chromium binding. Very good adsorption capacity and low cost or cost free of devil tree saw dust makes this biosorbent as one of the best adsorbents for removal of hexavalent chromium from contaminated water. © 2012 Canadian Society for Chemical Engineering  相似文献   

3.
Environmental pollution by heavy metals is currently a problem of great concern for human health. In this context, this study aims to contribute with the synthesis and characterization of chitosan functionalized with three different ionic liquids (n-butylammonium acetate, sec-butylammonium acetate, and tert-butylammonium acetate) followed by its application in hexavalent chromium effluent treatment. The adsorbents synthesized (ChN, ChS, and ChT) were characterized by SEM, EDS, FTIR, BET, RDD, PSD, and XRD techniques. Afterward, the influences of temperature, contact time, and pH on the Cr(VI) adsorption process were evaluated. The solution with pH 3 displayed the highest adsorption capacities (107.31, 104.60, and 107.97 mg.g-1 for ChN, ChS, and ChT, respectively). The kinetic data were better adjusted to the Weber-Morris kinetic model with an ideal time of 2 h. Furthermore, the influence of temperature was evaluated using the Freundlich and Langmuir isotherms, with maximum capacities of 142.05 (ChN), 131.58 (ChS), and 146.63 mg.g-1 (ChT). The adsorbent displayed enhanced adsorption properties in comparison with raw chitosan by an intensification of the electrostatic interaction between amino groups and hexavalent chromium. Finally, the reusability was investigated, and significant results were observed (84.33 ± 4.87%) in the adsorption process after 4 cycles.  相似文献   

4.
The pollution of heavy metal ions in water poses a serious threat to human being and ecosystems. Here, we report polyamidoxime (PAO) brush grafted graphene oxide (GO) as a highly efficient adsorbent for extraction of toxic metal cations from water. Surface-initiated atom transfer radical polymerization was used to grow polyacrylonitrile (PAN) brushes on GO, followed by conversion of the nitrile groups in PAN into amidoxime groups, which had high binding affinity toward heavy metal cations. The PAO brush grafted GO demonstrated significantly fast adsorption kinetics and large adsorption capacity. At optimal pH 5, the PAO brush grafted GO can achieve maximum adsorption capacities of 116.7 mg g−1 for Pb(II), 258.6 mg g−1 for Ag(I), 192.2 mg g−1 for Cu(II), and 167.9 mg g−1 for Fe(III), which were significantly larger than those of small molecule functionalized GO. Mechanism analysis suggested that the enhanced adsorption performance was due to the myriads of functional groups in PAO brushes that were easily accessible to metal ions because of the swelling of the polymer brushes in water. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48156.  相似文献   

5.
Environmental pollution with heavy metals, especially with hexavalent chromium, is a serious problem worldwide. Therefore, in this study, the synthesis, characterization, and application of a heavy metal bioadsorbent, CMCCHDIC, were carried out. Carboxymethylcellulose (CMC) was synthesized from corn stover and reacted with chitosan (CH) using N,N′-diisopropylcarbodiimide (DIC) as a coupling reagent to obtain CMCCHDIC. CMC and CMCCHDIC were characterized by granulometric distribution of microparticles, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and nuclear magnetic resonance. The ideal conditions for CMCCHDIC adsorption were determined, and 180 min of contact time, pH 2.5, and 293 K were observed to yield the best adsorption capacity. An increase in the adsorption capacity of CMCQDIC (qe = 115.78 ± 0.17 mg∙g−1) to 81.5% relative to that of pure CH (qe = 63.78 ± 0.48 mg∙g−1) was observed, and the reduction of solubility in acidic media comparing with CH, which favors the application of the bioadsorbent synthetized.  相似文献   

6.
The adsorption capabilities of multiwalled carbon nanotubes (MWCNTs) with and without the embedded carboxyl group for the removal of parts per million levels of hexavalent chromium were examined as a function of several parameters, namely contact time, pH of initial solution, initial concentration of Cr(VI), adsorbent dosage as well as temperature of solution. Adsorption isotherms have been utilized to explain the adsorption mechanism. Ion exchange, intra‐particle diffusion, and electrostatic interactions are found to be the fundamental mechanisms describing the adsorption of Cr(VI). The maximum adsorption capacities of Cr(VI) ion by raw MWCNTs and functionalized MWCNTs were found to be 84.75 and 78.13 mg · g?1, respectively, as calculated by the Langmuir adsorption isotherm model. This is with regard to the electron‐rich atoms inside the functional group which repels the negatively charged dichromate ions. Kinetic studies were performed, and the data was found in good agreement with the pseudo‐second‐order.  相似文献   

7.
Nanostructured chitosan/polyaniline (CH/PANI) hybrid was synthesized via in situ polymerization of aniline in the presence of chitosan. The CH/PANI hybrid was characterized by FTIR spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The CH/PANI hybrid had a nanofibrous structure with an average diameter of 70 nm. This hybrid was employed as an ecofriendly and efficient adsorbent with high adsorption capacity for the removal of Acid Green 25 (AG) and methylene blue (MB) from aqueous solutions. AG and MB were used as anionic and cationic model dyes, respectively. The CH/PANI adsorbent showed high dependence on the pH of the medium with an excellent adsorption performance and regeneration manner. The kinetics and adsorption isotherms were studied. The CH/PANI hybrid follows the pseudo second-order adsorption kinetics and Temkin isotherm model for the adsorption of both AG and MB dyes. This assumes that the enthalpy of dyes molecules decreases with the adsorption on heterogeneous surface with various kinds of adsorption sites and as well as the ability to form multilayers of the dye. Also, intraparticle diffusion was found to play an important role in the adsorption mechanism. The maximum adsorption capacity was found to be 240.4 mg g−1 of AG at pH 4 and 81.3 mg g−1 of MB at pH 11. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47056.  相似文献   

8.
Sorption of hexavalent chromium ions from aqueous solution by poly 4‐vinyl pyridine [Poly(4‐VP)] was studied. The batch method was applied for adsorption processes. The effects of initial ion concentration, time, pH and temperature on adsorption were investigated. A treatment time of 60 min was found to be sufficient to reach equilibrium. pH 3.0 was found as the optimum pH value for the process. The maximum adsorption performance was achieved at 86.7 mg g?1 using 500 mg L?1 Cr (VI) solutions. The process of adsorption of Cr (VI) was explained by Langmuir isotherm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2865–2870, 2006  相似文献   

9.
《分离科学与技术》2012,47(1):111-122
Abstract

A possibility of Cr(VI) removal by the adsorption method is discussed in the paper. An adsorbent were hydrogel chitosan beads are produced by the phase inversion method (by changing pH). The possibility of removing Cr(VI) ions by both pure chitosan hydrogel and its chelate compounds (chitosan cross‐linked with Cu(II) and Ag(I) ions) was investigated. The adsorption proceeded from the solutions of potassium dichromate and ammonium dichromate (NH4)2Cr2O7 and K2Cr2O7. The process rates and adsorption isotherms were determined and described by relevant equations. The process rate was described by the pseudo‐ and second‐order equations, and adsorption equilibria by the Langmuir equations. A slight advantageous change in adsorption properties of chitosan beads was revealed after cross‐linking (for chromium concentration up to 10 g/dm3). A maximum adsorption was 1.1 gCr/g chitosan. Results of the studies show that chitosan hydrogel proves useful in the removal of Cr(VI) ions, additionally, cross‐linking with Cu(II) and Ag(I) ions has an advantageous effect in the case of low‐concentrated solutions.  相似文献   

10.
Modified activated carbon are carbonaceous adsorbents which have tetrabutyl ammonium iodide (TBAI) and sodium diethyl dithiocarbamate (SDDC) immobilised at their surface. This study investigates the adsorption of toxic ions, copper, zinc, chromium and cyanide on these adsorbents that have undergone surface modification with tetrabutyl ammonium (TBA) and SDDC in wastewater applications. The modification technique enhance the removal capacity of carbon and therefore decreases cost-effective removal of Cu(II), Zn(II), Cr(VI) and CN from metal finishing (electroplating unit) wastewater. Two separate fixed bed modified activated carbon columns were used; TBA-carbon column for cyanide removal and SDDC-carbon column for multi-species metal ions (Cu, Zn, Cr) removal. Wastewater from electroplating unit containing 37 mg l−1 Cu, 27 mg l−1 Zn, 9.5 mg l−1 Cr and 40 mg l−1 CN was treated through the modified columns. A total CN removal was achieved when using the TBA-carbon column with a removal capacity of 29.2 mg g−1 carbon. The TBA-carbon adsorbent was found to have an effective removal capacity of approximately five times that of plain carbon. Using SDDC-carbon column, Cu, Zn and Cr metal ions were eliminated with a removal capacity of 38, 9.9 and 6.84 mg g−1, respectively. The SDDC-carbon column has an effective removal capacity for Cu (four times), Zn (four times) and Cr (two times) greater than plain carbon.  相似文献   

11.
Due to the low concentration of silver in water, most of the cellulose adsorbents exhibited low removal efficiency, which greatly limited their practical applications. Herein, a cellulose aerogel modified by thiosemicarbamide (CAT) was fabricated for reducing and adsorbing silver ions from low concentration wastewater. The characterization results concluded that CAT owned a three-dimensional spongy structure with many circular microspheres and a better specific surface area (19.37 m2 g−1), as well as the functional groups of ─C═N+─H and ─(C═S)─N. The static batch adsorption experiments demonstrated that CAT could reached the maximum removal percentage of 94.94% and adsorption capacity of 42.12 mg g−1 under the initial concentration of Ag(I) was 15 mg L−1 and the pH value was 7. Meanwhile, the adsorption of Ag(I) on CAT was second-order reaction, and the Langmuir model could better fit the adsorption process. In addition, CAT exhibited wide pH values (1–9) adaptability and excellent adsorption performance for silver through electrostatic interaction, chelation, and reduction. This study probably provides a new method as well as important experimental data and theoretical reference for the removal of silver ions and other metals.  相似文献   

12.
Epichlorohydrin cross-linked chitosan microspheres (CS) and chitosan–heparin polyelectrolyte complex microspheres (CSH) were used in the adsorption of copper (II) ions in aqueous solution. The chitosan microspheres were prepared by the phase inversion method. The use of a cross-linking agent improved the resistance to acidic medium. Polyelectrolyte complex microspheres were prepared by impregnating heparin in cross-linked chitosan microspheres. The microspheres were characterized by IR, TGA and DSC. A study on the effect of the pH on the adsorption of copper (II) ions showed that the optimum pH for both CS and CSH microspheres was 6.0. From a kinetic evaluation, it could be established that the adsorption equilibrium was achieved after 8 h for CS and 25 h for CSH microspheres. The adsorption isotherms were interpreted using Langmuir and Freundlich mathematical models. The results revealed that experimental data of CS was best adjusted by Langmuir model, with maximum capacity of surface saturation equal to 39.31 mg g−1. On the other hand, Langmuir and Freundlich models provided a good fit for adsorption by CSH and the adsorption capacity was 81.04 mg g−1. The interactions between copper (II) ions and both CS and CSH were confirmed by electron paramagnetic resonance spectroscopy, which revealed the formation of a square-planar complex with tetrahedral distortion on the surface of the adsorbents.  相似文献   

13.
BACKGROUND: Poly(HEMA‐co‐MMA) beads were prepared from 2‐hydroxyethyl‐methacrylate (HEMA) and methylmethacrylate (MMA) in the presence of FeCl3. Thermal co‐precipitation of Fe(III) ions containing beads with Fe(II) ions was carried out under alkaline conditions. The magnetic beads were grafted with poly(glycidylmethacrylate; p(GMA)), and the epoxy groups of the grafted p(GMA) brushes were converted into amino groups by reaction with ammonia. RESULTS: The magnetic beads were characterized by surface area measurement, electron spin resonance (ESR), Mössbauer spectroscopy and scanning electron microscopy (SEM). The maximum adsorption of Reactive Green‐19 (RG‐19) dye on the p(GMA) grafted and amine modified magnetic beads was around pH 3.0. The adsorption capacity of magnetic beads was 84.6 mg dye g?1. The effects of adsorbent dosage, ionic strength and temperature have also been reported. Batch kinetic sorption experiments showed that a pseudo‐second‐order rate kinetic model was applicable. CONCLUSION: The p(GMA) grafted and amine modified magnetic beads (adsorbent) were expected to have the advantage of mobility of the grafted chains in the removal of acidic dyes from aqueous solutions. The magnetic beads have potential as an adsorbent for removal of pollutants under various experimental conditions without significant reduction in their initial adsorption capacity. Copyright © 2011 Society of Chemical Industry  相似文献   

14.
A new chitosan molecular‐imprinted adsorbent was prepared from the mycelium of waste biomass. The results showed that an adsorbent using Penicillium chrysogenum mycelium as the core material was better than one derived from peanut coat. The adsorption capacity of the surface‐imprinted adsorbent for Ni2+ was enhanced by increasing the chitosan concentration in the imprinting process. Epichlorohydrin was better than glutaraldehyde as a cross‐linking agent; the optimal imprinted Ni2+ concentration for preparing the surface‐imprinted adsorbent was 2 mg (Ni2+) g?1 of mycelium. The adsorption capacity of the surface‐imprinted adsorbent was 42 mg g?1 (at 200 mg dm?3 initial metal ions concentration) and twice that of the mycelium adsorbent. The surface‐imprinted adsorbent can be reused for up to 15 cycles without loss of adsorption capacity. Copyright © 2005 Society of Chemical Industry  相似文献   

15.
A novel chitosan-based adsorbent (CCTM) was prepared by the reaction of epichlorohydrin O-crosslinked chitosan with maleic anhydride under microwave irradiation. The chemical structure of this polymer was characterized by infrared spectroscopy and X-ray diffraction analyses. The effects of various variables such as degree of substitution, adsorption time, initial metal ion concentration, solution pH, and temperature, on the adsorption of Pb2+ and Cu2+ by CCTM were investigated. The results demonstrate that the microwave irradiation can remarkably enhance the reaction. CCTM has higher adsorption capacity than chitosan. The maximum adsorption capacities for Pb2+ and Cu2+, with initial concentrations of 0.02 mol L−1 at pH 5, are 246.3 and 132.5 mg g−1, respectively. The adsorbent can be recycled. These results have important implications for the design of effective chitosan-based adsorbents in the removal of heavy metal ions from wastewaters. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

16.
This study aimed at immobilizing Reactive Blue 2 (RB 2) dye in chitosan microspheres through nucleophilic substitution reaction. The adsorbent chemical modification was confirmed by Raman spectroscopy and thermogravimetric analysis. This adsorption study was carried out with Cu(II) and Ni(II) ions and indicated a pH dependence, while the maximum adsorption occurred around pH 7.0 and 8.5, respectively. The pseudo second-order kinetic model resulted in the best fit with experimental data obtained from Cu(II) (R = 0.997) and Ni(II) (R = 0.995), also providing a rate constant, k2, of 4.85 × 10−4 and 3.81 × 10−4 g (mg min)−1, respectively, thus suggesting that adsorption rate of metal ions by chitosan-RB 2 depends on the concentration of ions on adsorbent surface, as well as on their concentration at equilibrium. The Langmuir and Freundlich isotherm models were employed in the analysis of the experimental data for the adsorption, in the form of linearized equations. Langmuir model resulted in the best fit for both metals and maximum adsorption was 57.0 mg g−1 (0.90 mmol g−1) for Cu(II) and 11.2 mg g−1 (0.19 mmol g−1) for Ni(II). The Cu(II) and Ni(II) ions were desorbed from chitosan-RB 2 with aqueous solutions of EDTA and H2SO4, respectively.  相似文献   

17.
The layered material of sodium ferric silicate (SFS) has good adsorption properties for cationic dyes, but its stacking properties limit its application. The organic–inorganic composite assembled by macromolecular polymer and inorganic material can improve this situation. Carboxymethyl chitosan (CC) was loaded onto SFS, and the compound was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscope (TEM), Brunauer–Emmett–Teller (BET), zero energy thermonuclear assembly (Zeta), and Fourier transform infrared spectroscopy (FT-IR). The results showed that CC was successfully supported in the layered structure of SFS, and the adsorption capacity of the composite for methylene blue (MB) was 729.67 mg g−1. The adsorption process was described by pseudo second-order kinetics, Langmuir isothermal equation, and intraparticle diffusion. The adsorption process was endothermic and spontaneous, and the monomolecular adsorption was dominant.  相似文献   

18.
Regenerated cellulose wood pulp was grafted with the vinyl monomer glycidyl methacrylate (GMA) using ceric ammonium nitrate as initiator and was further fuctionalised with imidazole to produce a novel adsorbent material, cellulose‐g‐GMA‐imidazole. All cellulose, grafted cellulose and functionalized cellulose grafts were physically and chemically characterized using a number of analytical techniques, including elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential thermal analysis, and scanning electron microscopy. The cellulose‐g‐GMA material was found to contain 1.75 mmol g?1 epoxy groups. These epoxy groups permitted introduction of metal binding functionality to produce the cellulose‐g‐GMA‐imidazole final product. Following characterization, a series of adsorption studies were carried out on the cellulose‐g‐GMA‐imidazole to assess its capacity in the removal of Cu2+ ions from solution. Cellulose‐g‐GMA‐imidazole sorbent showed an uptake of ~70 mg g?1 of copper from aqueous solution. The adsorption process is best described by the Langmuir model of adsorption, and the thermodynamics of the process suggest that the binding process is mildly exothermic. The kinetics of the adsorption process indicated that copper uptake occurred within 30 min and that pseudo‐second‐order kinetics best describe the overall process. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 2006  相似文献   

19.
This work developed an effective way to improve the methylene blue (MB) adsorption performance of cellulose-based hydrogel by modified with tannic acid (TA). HEC-co-p(AA-AM)/TA hydrogel was synthesized by grafting of acrylic acid (AA) and acrylamide (AM) onto hydroxyethyl cellulose (HEC), followed by modified with TA. Fourier transform infrared spectroscopy manifested that AA and AM were successfully grafted onto the hydrogel, and TA was immobilized in the hydrogel. Field emission scanning electron microscope demonstrated that the hydrogel after TA modification had a homogeneous pore structure. Brunauer-Emmett-Teller (BET) surface areas, total pore volume, and average pore diameters of the hydrogel are 11.821 m2 g−1, 0.0641 cm3 g−1, and 2.538 nm, respectively. The high swelling ratio (1179.2 g g−1 in deionized water) was in favor of the MB adsorption. The results of the adsorption experiments illustrated that HEC-co-p(AA/AM) hydrogel had excellent MB adsorption performance. As the pH increases, the electrostatic attraction is enhanced, and the adsorption capacity is improved. The adsorption process was more fit with pseudo-second-order kinetics, and the maximum adsorption capacity (3438.27 mg g−1) was determined by Langmuir model. Thermodynamic studies suggested that the adsorption process is spontaneous, exothermic, and entropy reduction. X-ray photoelectron spectroscopy analysis confirmed that MB molecules were reacted with the oxygen atoms in hydroxyl and carboxyl groups by ion-exchange. High reusability demonstrated that the hydrogel could be a potential candidate for removal cationic dye from industrial effluents.  相似文献   

20.
In this study, novel affinity chromatographic fibers was prepared from methacrylamide grafted poly(ethylene terephthalate), PET-g-pMAA, using benzoylperoxide as an initiator. A dye ligand (i.e., Procion Brown) as a ligand was then covalently immobilized on the different amount of pMAAm grafted PET fibers, (PET-g-pMAAm-PB). The fibers were characterized by surface area measurement, infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Adsorptive properties of the composite fibers were tested using a model protein (i.e., lysozyme). To achieve these purposes, the influence of pH, ionic strength, initial lysozyme concentration, and temperature on adsorption system has been investigated and evaluated. A maximum lysozyme adsorption PET-g-pMAAm-PB fiber was obtained as 43.9 mg g−1 at pH 7.5. The experimental equilibrium data obtained for lysozyme adsorption onto PET-g-pMAAm-PB fibers fitted well to the Langmuir isotherm model. The result of kinetic analyzed for lysozyme adsorption onto affinity fibers showed that the second-order rate equation was favorable. The purity of the eluted lysozyme, as determined by HPLC, was 84% with recovery 73% for PET-g-pMAAm-PB fiber. Experiments on regeneration and dynamic adsorption were also performed. It appears that PET-g-pMAAm-PB fibers can be applied for lysozyme separation without causing any denaturation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号