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1.
The most appropriate method in designing the adsorption systems and assessing the performance of the adsorption systems is to have an idea on adsorption isotherms. Comparison analysis of linear least square method and nonlinear method for estimating the isotherm parameters was made using the experimental equilibrium data of Zn(II) and Cu(II) onto kaolinite. Equilibrium data were fitted to Freundlich, Langmuir, and Redlich–Peterson isotherm equations. In order to confirm the best-fit isotherms for the adsorption system, the data set using the chi-square (χ 2), combined with the values of the determined coefficient (r 2) was analyzed. Nonlinear method was found to be a more appropriate method for estimating the isotherm parameters. The best fitting isotherm was the Langmuir and Redlich–Peterson isotherm. The Redlich–Peterson is a special case of Langmuir when the Redlich–Peterson isotherm constant g was unity. The sorption capacity of kaolinite to uptake metal ions in the increasing order was given by Cu (4.2721 mg/g)?<?Zn (4.6710 mg/g).  相似文献   

2.
Biofilms wasted from biotrickling filters was dried and used as biosorbent for Cd(II) removal from aqueous solutions. The adsorption condition and effect, adsorption isotherms and kinetics of Cd(II) removal were investigated, and the effects of competitive metal ions on Cd(II) removal were also examined. Results showed that the dry waste biofilms reached the maximum adsorption capacity of 42 mg/g of Cd(II) at 25 °C for 120 min when the initial concentration of Cd(II) and their pH were 50 mg/L and 6.0, respectively. Under these conditions, the removal efficiency of Cd(II) reached to 89.3% when the biosorbent dosage was 2.0 g/L. The Langmuir isotherm model correlated with the isotherm data better than the Freundlich isotherm model, and the pseudo-second-order model fitted the kinetic data better than the pseudo-first-order model. These results indicated that the adsorption was monolayer accompanied with chemical adsorption. In the presence of other metal ions, divalent metal ions of Ca and Zn inhibited the performance of Cd(II) biosorption significantly, while Na(I), K(I) and Fe(III) which had a higher or lower valence than Ca(II) affected slightly when containing 50 mg/L Cd(II), 0.5 g/L adsorbent dosage and pH 6.0. The analyses of scanning electron microscopy and Fourier transform infrared spectroscopy illuminated that the biosorbent had porous structures and the amide group was the majorly responsible for Cd(II) removal. Dry biofilms were novel sorbents for effective removal Cd(II), and it could be reused and recycled if necessary.  相似文献   

3.
In this research, the equilibrium sorption of Zn(II) and Cu(II) by kaolinite was explained using the Freundlich, Langmuir and Redlich–Peterson isotherms, via both linear and non-linear regression analyses. In the case of non-linear regression method, the best-fitting model was evaluated using six different error functions, namely coefficient of determination (r 2), hybrid fractional error function (HYBRID), Marquardt’s percent standard deviation (MPSD), average relative error (ARE), sum of the errors squared (SSE) and sum of the absolute errors (EABS). The examination of error estimation methods showed that the Langmuir model provides the best fit for the experimental equilibrium data for both linear and non-linear regression analyses. The SSE function was found to be a better option to minimize the error distribution between the experimental equilibrium data and predicted two-parameter isotherms. In the case of three-parameter isotherm, HYBRID was found to be the best error function to minimize the error distribution structure between experimental equilibrium data and theoretical isotherms. Non-linear method was found to be more appropriate method for estimating the isotherm parameters.  相似文献   

4.
Amorphous tin(VI) hydrogen phosphate (ATHP) was synthesized using the liquid phase precipitation method and served as an adsorbent to remove Pb(II), Cu(II), and Zn(II) from aqueous solutions. The ATHP was characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption techniques. Adsorption properties were evaluated as a function of pH, reaction time, concentration of reactants, and salinity. Their equilibrium adsorption data were modeled using Freundlich, Langmuir, and Dubinin–Kaganer–Radushkevich isotherms, respectively. The results revealed that adsorption equilibrium reached within 180 min. ATHP indicated good adsorption even below the pHZPC, and best adsorption at pH 5 for Pb(II) and Cu(II) and at pH 5.5 for Zn(II) was observed. Equilibrium data fitted better to the Langmuir model for Pb(II) and Cu(II) and fitted better to the Freundlich model for Zn(II). The saturated adsorption capacities deduced from the Langmuir model were 2.425, 1.801, and 0.600 mmol/g for Cu(II), Pb(II), and Zn(II), respectively, indicating an adsorption affinity order of Cu > Pb > Zn. There is a negative correlation between the concentration of NaCl and adsorption capacity of ATHP, yet ATHP still exhibited excellent adsorption having an adsorption capacity of 19.35, 15.16, 6.425 mg/g when the concentration of NaCl was 0.6 mol/L. The free energy (E) was 12.33, 10.70, and 14.74 kJ/mol for Pb(II), Cu(II), and Zn(II), respectively. An adsorption mechanism based on ion exchange between heavy metal ions and H+ in the ATHP is proposed. Furthermore, the used ATHP was regenerated by HCl solution and the adsorbent was used repeatedly.  相似文献   

5.
The potential use of the immobilized microalgae (in Ca-alginate) of Chlamydomonas reinhardtii to remove Hg(II), Cd(II) and Pb(II) ions from aqueous solutions was evaluated using bare Ca-alginate bead as a control system. Ca-alginate beads containing immobilized microalgae were incubated for the uniform growth at 22 °C for 5 days. Effects of pH, temperature, initial concentration of metal ions and biosorbent dosages on the adsorption of Hg(II), Cd(II) and Pb(II) ions were studied. Adsorption of Hg(II), Cd(II) and Pb(II) ions on the immobilized microalgae showed highest values at around pH 5.0 to 6.0. The adsorption equilibrium was represented with Langmuir and Freundlich adsorption isotherms. The adsorption of these ions on the immobilized microalgae followed second-order kinetics and equilibrium was established in about 60 min. The temperature change in the range of 5–40 °C did not affect the adsorption capacities of the immobilized microalgae. The immobilized-algal systems can be regenerated using 2 M NaCl for Hg(II), Cd(II) and Pb(II) ions.  相似文献   

6.
The biosorption characteristics of Cd(II) and Cu(II) ions from aqueous solutions obtained using submerged aquatic plant (Myriophyllum spicatum) biomass were investigated in terms of equilibrium, kinetics, thermodynamics, and cation competition. Langmuir and Freundlich models were applied to describe the biosorption isotherm of metal ions by M. spicatum biomass and isotherm constants considering the most important parameter, pH. The variation of sorption isotherm constants showed pH dependence. The Langmuir and Freundlich models fitted the equilibrium data well. The maximum biosorption capacity (q m) of M. spicatum biomass was determined to be 29.07 mg/g for the Cd(II) ion at pH 5.0 and 12.12 mg/g for the Cu(II) ion at pH 6.0. Chi square analysis showed that the Freundlich model fitted the equilibrium data better than the Langmuir isotherm. Competition of Cd(II) and Cu(II) in a binary solution showed that the Langmuir monolayer capacity of Cd(II) decreased from 29.07 mg/g with only Cd(II) in solution to 12.02 mg/g in the presence of Cu(II). Kinetics results showed that the biosorption processes of both metal ions followed the pseudo-second-order kinetics well. The calculated thermodynamic parameters (?G 0, ?H 0, and ?S 0) showed that biosorption of Cd(II) and Cu(II) ions onto M. spicatum biomass was feasible, spontaneous, and endothermic in nature. Fourier transform infrared spectroscopy spectrum analysis revealed that Cd(II) and Cu(II) sorption was mainly ascribed to carboxyl, hydroxyl, amine, and C–N groups in M. spicatum.  相似文献   

7.
In this study, the adsorption behavior of Ni(II) in an aqueous solution system using natural adsorbent Peganum harmala-L was measured via batch mode. The prepared sorbent was characterized by scanning electron microscope, Fourier transform infrared spectroscopy, N2 adsorption–desorption and pHzpc. Adsorption experiments were carried out by varying several conditions such as contact time, metal ion concentration and pH to assess kinetic and equilibrium parameters. The equilibrium data were analyzed based on the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms. Kinetic data were analyzed using the pseudo-first-order, pseudo-second-order and intra-particular diffusion models. Experimental data showed that at contact time 60 min, metal ion concentration 50 mg/L and pH 6, a maximum amount of Ni(II) ions can be removed. The experimental data were best described by the Langmuir isotherm model as is evident from the high R 2 value of 0.988. The adsorption capacity (q m) obtained was 68.02 mg/g at an initial pH of 6 and a temperature of 25 °C. Kinetic studies of the adsorption showed that equilibrium was reached within 60 min of contact and the adsorption process followed the pseudo-first-order model. The obtained results show that P. harmala-L can be used as an effective and a natural low-cost adsorbent for the removal of Ni(II) from aqueous solutions.  相似文献   

8.
The ability of ochre to remove Pb(II) and Cu(II) from aqueous media has been studied by batch sorption studies varying the contact time, initial metal concentration, initial solution pH and temperature to understand the adsorption behaviour of these metals through adsorption kinetics and isotherms. The pH of the solution and the temperature controlled the adsorption of metal ions by ochre and rapid uptake occurred in the first 30 min of reaction. The kinetics of adsorption followed a pseudo-second-order rate equation (R 2 > 0.99) and the isotherms are well described by the Freundlich model. Adsorption of metals onto ochre is endothermic in nature. Between the two metals, Pb(II) showed more preference towards the exchangeable sites on ochre than Cu(II). This study indicates that ochre is a very effective adsorbent in removing Pb(II) and Cu(II) from the aqueous environment with an adsorptive capacity of 0.996 and 0.628 mg g?1 and removal efficiency of 99.68 and 62.80 %, respectively.  相似文献   

9.
The adsorption of cadmium (Cd) and zinc (Zn) with similar chemical properties is examined onto three soil samples: one is alkaline and the others are acidic. The distribution coefficient (K d) and the Freundlich constant (K F) for Zn are slightly higher than those for Cd, implying that the adsorption affinity of Zn is a little greater and less mobile. However, Cd and Zn usually show comparable results in the kinetic, isotherm, and envelope experiments. The adsorption of the heavy metals is relatively rapid and the reaction is almost completed within 15 min. The kinetics for both Cd and Zn are very well explained by the parabolic diffusion model. The maximum adsorption of the heavy metals is obtained at high pH, high temperature, and low ionic strength. The adsorption capacity on the alkaline soil is more significantly affected by the temperature as compared to the acidic soil. It is found that the adsorption affinity of the two heavy metals is mainly affected by the soil properties, such as pH, pHPZC, organic matter, and total carbon. It is also confirmed that the chemical properties of the heavy metals are important factors in their adsorption onto soil. The adsorption isotherms of Cd and Zn are well described in both Freundlich and Langmuir models at the usual pH (soil pH). Under acidic and alkaline pHs, however, only the Freundlich model describes the adsorption of both heavy metals satisfactorily.  相似文献   

10.
Adsorptive separation of Pb(II) and Cu(II) using modified waste Lyocell fiber adsorbent was investigated in this research. The waste Lyocell fiber was functionalized through carboxymethylation of the hydroxyl moieties using sodium chloroacetate as modifying agent and was crosslinked with epichlorohydrin to provide water stability. The maximum equilibrium batch uptake in single metal system was 353.45 mg/g for Pb(II) and 98.33 mg/g for Cu(II), according to the Langmuir isotherm model. The adsorption rates were very fast and reached equilibrium within 3 and 5?10 min for Cu(II) and Pb(II), respectively. In competitive binary metal system, the uptake of Cu(II) largely decreased to 38.40 mg/g, and Pb(II) selectivity was observed. Elemental and functional characterization suggested that the adsorption proceeded by ion exchange between the adsorbent and metal ions. In a flow-through column system, adsorption followed by desorption aided in effectively eluting ~260 mg of Pb(II) (out of ~300 mg total adsorbed) from the Pb(II)–Cu(II) binary solution. Finally, the adsorbent was very effective in four successive adsorption–desorption cycles with over 99 % uptake and 94 % desorption efficiencies. The present study may provide an alternative option for waste fiber recycling and could be useful in recovering heavy metal ions from aqueous sources to complement their depleting reserves.  相似文献   

11.
A novel polyurethane foam/organobentonite/iron oxide nanocomposite adsorbent was successfully prepared via in situ polymerization of toluene diisocyanate and polyol in presence of 5 wt% organobentonite/iron oxide. The obtained nanocomposite was characterized in detail, and the results revealed that the clay layers are exfoliated and/or intercalated in the polymer matrix forming a nanocomposite structure. The application of the prepared nanocomposite for adsorption of cadmium ions from aqueous solution was tested as a function of various experimental parameters using batch procedures. Adsorptive removal of Cd(II) onto the nanocomposite attained maximum at adsorbent content 1.5 g/L, pH 6, and the equilibrium was established within 60 min. Kinetic studies showed that the experimental data fit very well to pseudo-second-order model, and the adsorption process proceeds through three steps. It was found that external liquid film and intraparticle diffusion steps deeply affect the rate of Cd2+ ions adsorption onto the synthesized nanocomposite. Langmuir isotherm model fitted the adsorption data better than Freundlich with a maximum adsorption capacity (q m) for Cd(II) equal to 78 mg/g under the specified experimental conditions. The synthesized nanocomposite afforded effective extraction for Cd2+ ions from natural water samples and excellent reusability feature. This study declares the potential efficiency of a new clay/polymer nanocomposite as alternative for wastewater remediation.  相似文献   

12.
In the present study, the retention capacity of carbonaceous material obtained from the diesel engine exhaust mufflers for Cr(VI) removal has been investigated. The physicochemical properties such as density, pH of aqueous slurry, pH at point of zero charge, ash content, moisture content, volatile matter, surface area, scanning electron microscopy and electron dispersive spectroscopy of the carbonaceous material were determined. The capacity of adsorbent for removal of Cr(VI) from aqueous solution was observed under different experimental condition like contact time, initial concentration of metal ions, pH and temperatures on the adsorption capacity of the adsorbent. Maximum adsorption of Cr(VI) ions was found at low pH. The adsorption process was found to follow second-order kinetics. The rate constant was evaluated at different temperatures along with other thermodynamic parameters like activation energy, Gibbs free energy change, enthalpy change and entropy change. Both Langmuir and Freundlich isotherms were used to describe the adsorption equilibrium of carbonaceous material at different temperatures. Langmuir isotherm shows better fit than Freundlich isotherm at given conditions. The result shows that low-cost carbonaceous material from diesel engine exhaust mufflers can be efficiently used for wastewater treatment containing Cr(VI) ions.  相似文献   

13.
A hydrophilic kapok fiber was prepared by a chemical process of the Fenton reaction and used as an adsorbent to remove Pb(II) from aqueous solution. The effects of experimental parameters including pH, contact time, Pb(II) concentration, and coexisting heavy metals were estimated as well as evaluated. The optimum concentrations of FeSO4 and H2O2 for the Fenton reaction-modified kapok fiber (FRKF) were 0.5 mol L?1 and 1 mol L?1, respectively. The adsorption kinetic models and isotherm equations of Langmuir and Freundlich were conducted to identify the most optimum adsorption rate and adsorption capacity of Pb(II) on FRKF. The FRKF displayed an excellent adsorption rate for Pb(II) in single metal solution with the maximum adsorption capacity of 94.41?±?7.56 mg g?1 at pH 6.0. Moreover, the FRKE still maintained its adsorption advantage of Pb(II) in the mixed metal solution. The FRKF exhibited a considerable potential in removal of metal content in wastewater streams.  相似文献   

14.
In recent years, the need for safe and economical methods to eliminate heavy metals from contaminated waters has necessitated research on the production of low-cost alternatives to commercially available activated carbon. In the present work, in order to enhance the removal of heavy metals from contaminated water, Zizyphus vulgaris wastes were modified chemically to produce an adsorbent rich in carboxylic groups to enhance the removal of heavy metals from contaminated water. Adsorption of Zn(II) ions on the produced adsorbent was then optimized. The optimal ratio for esterification involved the treatment of Z. vulgaris wastes (1 g) with 0.0037 mmol malic acid in the presence of a very small amount of water for 2 h at 140 °C. The maximum values for adsorption capacity, q max, were 28.7 and 164.6 mg/g on native and modified Z. vulgaris wastes, respectively, at pH 5 and 30 °C with a contact time 2 h and an initial metal ion concentration of 400 mg/L. The equilibrium data were well fitted by the Langmuir and Freundlich adsorption models and demonstrated the significant capacity for Z. vulgaris wastes in the removal of Zn(II) ions from aqueous solutions.  相似文献   

15.
A novel two-dimensional carbon material using phytic acid-functionalized graphene oxide was successfully synthesized by a simple hydrothermal method. Properties of the material were characterized by SEM, FT-IR, FITR-Rama and BET. Some factors like contact time, pH, and temperature were studied to investigate the adsorption characteristics on Cu(II) ions of the material. Experiment results showed that the material can reach equilibrium adsorption in 20 min and get maximum adsorption capacity (316.586 mg g) under the condition of pH 4.0, 304 K. The adsorption of Cu(II) ions was an exothermic and spontaneous process, and could be better simulated by the pseudo-second-order kinetics and Freundlich isotherm model.  相似文献   

16.
In this study, the imprinted aniline–formaldehyde was used as an adsorbent for removal of Iridium and Palladium ions from aqueous solutions through batch equilibrium. The sorbent was characterized by fourier transform infrared spectroscopy. The influence of pH, equilibrium time, temperature and initial concentration of metal ions on adsorbed amount of both ions were investigated. The maximum adsorption capacity in initial concentration of 100 mg/L was found to be 12.5 mg/g at pH 7.0 and 14.3 mg/g at pH 8.0 for Iridium and Palladium, respectively. In addition, the best desorption of the metal ions from resin was obtained by 0.5 mol/L nitric acid as eluting agent. The profile of both ions uptake on this sorbent reflects good accessibility of the chelating sites in the imprinted aniline–formaldehyde. Langmuir, Freundlich, Temkin and Redlich–Peterson isotherm models were applied to analyze the experimental data. Moreover, Langmuir linear method was used to obtain the isotherm parameters. However, Langmuir type II achieved the highest coefficient which led to the best fit for the palladium and the best fit for Iridium obtained from linear Redlich–Peterson. However, the thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were also determined using the equilibrium constant values obtained at different temperatures. The results showed that the adsorption for Iridium and Palladium ions was spontaneous nature and endothermic. Moreover, the method was applied for the determination of both ions from tap water samples.  相似文献   

17.
In the present experimental study, solid waste was used as an adsorbent and the effectiveness of the adsorbent was increased by novel treatment methods. Red mud, acid-treated activated red mud and iron oxide-coated acid-treated activated red mud were used for the removal of lead (II). The structural and functional groups were identified to confirm the removal of lead (II) by powder X-ray diffraction and Fourier transform infrared spectroscopy analyses. The enhancement of surface area was confirmed by Brunauer–Emmett–Teller analysis. Batch adsorption experiment was also conducted, and various parameters such as the effect of adsorbent dosage, pH, contact time and initial ion concentration were analyzed and reported. Adsorption equilibrium data were investigated using Langmuir, Freundlich and Dubinin–Radushkevich isotherm models with three parameters, and the rate of reaction was examined through kinetic models. The results indicate that in particular a novel modified form of red mud, namely iron oxide-coated acid-treated activated red mud was well fitted in lead (II) removal compared with reported adsorbents. The Langmuir isotherm shows that the maximum adsorption of adsorbate per gram was greater than other adsorbents (27.02 mg/g). In Freundlich isotherm, the Freundlich constant n values lie between 1 and 10 indicate the favorable adsorption. The calculated n values for normal red mud, acid-treated activated red mud and iron oxide-coated acid-treated activated red mud were found to be 1.9, 2.1 and 2.0 respectively. The correlation coefficient value was higher and the rate of reaction follows the pseudo-second-order kinetic model.  相似文献   

18.
Biosorption is an effective method to remove heavy metals from wastewater. In this work, the biosorption of Cd(II) onto Hydrilla verticillata was examined in aqueous solution with parameters of initial pH, adsorbent dosage, contact time, initial Cd(II) concentration, temperature, and co-existing ion. Linear Langmuir and Freundlich models were applied to describe the equilibrium isotherms, and both of the two models were fitted well. The monolayer adsorption capacity of Cd(II) was found to be 50 mg/g at pH 6 and 20°C. Dubinin–Radushkevich isotherm model was also applied to the equilibrium data. The mean free energy of adsorption (11.18 kJ/mol) indicated that the adsorption of Cd(II) onto H. verticillata might be carried out via chemical ion-exchange mechanism. Thermodynamic parameters, including free energy (∆G 0), enthalpy (∆H 0), and entropy (∆S 0) of adsorption, were also calculated. These results showed that the biosorption of Cd(II) onto H. verticillata was a feasible, spontaneous, and exothermic process in nature. Desorption experiments indicated that 0.01 mol/L EDTA and HNO3 were efficient desorbents for the recovery of Cd(II) from biomass. IR spectrum analysis suggested that amido, hydroxyl, C=O and C–O could combine strongly with Cd(II). EDX spectrum analysis suggested that an ion exchange mechanism might be involved.  相似文献   

19.
This paper reports the potential of chemically treated wood chips to remove copper (II) ions from aqueous solution a function of pH, adsorbent dose, initial copper (II) concentration and contact time by batch technique. The wood chips were treated with (a) boiling, (b) formaldehyde and (c) concentrated sulphuric acid and characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive analysis X-ray. pH 5.0 was optimum with 86.1, 88.5 and 93.9 % copper (II) removal by boiled, formaldehyde-treated and concentrated sulphuric acid-treated wood chips, respectively, for dilute solutions at 20 g L?1 adsorbent dose. The experimental data were analysed using Freundlich, Langmuir, Dubinin–Radushkevich and Temkin isotherm models. It was found that Freundlich and Langmuir models fitted better the equilibrium adsorption data and the adsorption process followed pseudo-second-order reaction kinetics. The results showed that the copper (II) is considerably adsorbed on wood chips and it could be an economical option for the removal of copper from aqueous systems.  相似文献   

20.
Surface modification of two algal biomasses, Nizimuddinia zanardini and Stoechospermum marginatum, using 4-phenyl-3-thiosemicarbazide ligand was performed to investigate the consequences on the adsorption of heavy metals from aqueous solution. Stabilization of amino group of 4-phenyl-3-thiosemicarbazide on the surface of biomasses was confirmed using Fourier transform infrared spectroscopy. Chemical modification was found to exert significant positive effects on biosorption. Adsorption capacities for Pb(II), Cd(II) and Cr(VI) using modified N. zanardini were observed to be 19.3, 16.75 and 15.75 mg/g, respectively, compared to 17.48, 14.18 and 11.85 mg/g for raw N. zanardini biomass. Also, adsorption of Pb(II), Cd(II) and Cr(VI) by the modified S. Marginatum was found to be 17.54, 15.62 and 14.77 mg/g, respectively, in comparison with that of the raw biomass which were 16.86, 12.9 and 11.2 mg/g. The obtained results of the equilibrium adsorption were studied through different isotherm models of Langmuir, Freundlich and Temkin, where the Langmuir model was observed to agree well with the results. Prevalent kinetic models including pseudo-second order and intra-particle diffusion were applied, and the pseudo-second order was found to describe the adsorption kinetics data adequately. Intra-particle model was also utilized in order to show penetration of metal ions, where it was realized that the biosorption took place in two or three steps including film diffusion, molecular diffusion and chemical reaction.  相似文献   

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