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 31 毫秒
1.
In this study, adsorption of Cu(II) onto the five locally abundantly low-cost biosorbents (Laminaria japonica, P. yezoensis Ueda, rice bran, wheat bran and walnut hull) was investigated depending on initial solution pH, contact time, adsorbent concentration and reaction temperature. Cu(II) removal was pH-dependent for various biosorbents investigated. For P. yezoensis Ueda, rice bran, wheat bran and walnut hull, the batch equilibrium data were correlated to Langmuir and Freundlich isotherms and the data fitted better to the Langmuir isotherm equation and yielded Langmuir monolayer capacity of 5.04, 10.41, 6.85 and 3.52 mg/g at the temperature of 20°C, respectively. In the case of Laminaria japonica, the equilibrium data obeyed the Hill-der Boer equation for the whole initial concentration ranges of 0–200 mg/L examined, but only to Langmuir and Freundlich equations for the initial concentration less than 120 mg/L at various temperatures. The apparent thermodynamic parameters were calculated for each of the five biosorbents (ΔH = 9.25–40.04 kJ/mol; ΔG = –17.60 to –24.16 kJ/mol and ΔS = 85.81–228 J/mol K). The numerical values obtained showed that Cu(II) adsorption is a spontaneous, entropy-driven and endothermic process. The batch kinetic data were correlated to the pseudo-first order and pseudo-second order models and the data fitted better to the pseudo-second order equation (the pseudo-second order rate constants, k2,e = 0.1059–0.9453 g/(mg min); the correlation coefficients, r = 0.9816–0.9993).  相似文献   

2.
《分离科学与技术》2012,47(3):681-711
Abstract

A timber industry waste was transformed to activated carbon by a one-step chemical activation process using H3PO4 (H). The used activated carbon (SDH) was characterized by N2 adsorption, FTIR, density, pH, point of zero charge pHpzc, moisture and ash content. Methylene blue (MB) and the iodine number were calculated by adsorption from the solution. The applicability of the different activated carbon produced was carried out to treatment of aqueous waste contaminated with iodine-labeled prolactin (I-PRL) Treatment processes were performed under the varying conditions; contact time, temperature, carbon type, carbon dosage, and different particle size of the activated carbon (SDH). The results indicated that 5 hours are sufficient to reach a plateau, and the amount of I-PRL adsorbed on SDH activated carbons increase with the solution temperature with thermodynamic parameter of ΔG° = ?7.962 (kJ/mol), ΔH° = 28.869 (kJ/mol) and ΔS° = 109.94 (J/mol K). The optimum adsorption results were reached using carbon dose of 0.1 gm with particle size of <0.25 mm, and a batch factor (V/M) of 7.14 mlg?1. First- and second-order equations, intraparticle diffusion equation, and the Elovich equation have been used to test experimental data. The experimental data was found to fit the second-order model and a chemisorptions mechanism. 0.7 M NaOH can be used for regeneration of spent SDH activated carbon with the efficiency of 99.6% and the regenerated carbon can be reused for five cycles effectively.  相似文献   

3.
This study aimed at preparing and optimizing an activated carbon (OAC) obtained from dry okra wastes by chemical activation with zinc chloride. Also, Rhodamine B removal performance from aqueous solution was analyzed by using this optimized activated carbon. The characterization of the resultant activated carbon, with a high surface area of 1044?m2/g, was carried out using thermogravimetric analysis, Brunauer–Emmett–Teller model, t-plot, N2 adsorption/desorption isotherms, density functional theory, elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and the point of zero charge. Furthermore, the effects of operating conditions (contact time, initial concentration, adsorbent dosage, temperature, and pH) on Rhodamine B adsorption onto OAC were investigated. Langmuir model was determined to be the best adsorption process, and the maximum adsorption capacity was calculated to be 321.50?mg/g at 25°C. Also, the intraparticle diffusion and boundary layer diffusion were involved in RhB adsorption onto OAC. Moreover, OAC adsorption curves of Rhodamine B followed pseudo second-order model. At 25°C, Gibbs free energy, enthalpy, and entropy obtained from thermodynamic studies were determined to be ?27.87?kJ/mol, 13.03?kJ/mol, and 0.15?kJ/mol K, respectively. These thermodynamic values revealed that Rhodamine B adsorption onto OAC was feasible, endothermic, physical, and spontaneous.  相似文献   

4.
Chao-Yin Kuo 《Desalination》2009,249(2):781-785
This study compares aqueous copper (II) adsorbed onto as-grown and modified carbon nanotubes (CNTs), using H2SO4 and H2SO4/KMnO4 processes. H2SO4 and H2SO4/KMnO4 modifications reduced pHiep and Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed that some functional groups were formed on modified CNTs. The adsorption capacity of copper (II) onto modified CNTs was greater than that of as-grown CNTs, especially at pH 6. The results demonstrate that the modified processes increased the adsorption capacity because the functional groups were generated on the modified surfaces of the CNTs. Additionally, the adsorption capacity of copper (II) onto as-grown and modified CNTs both increased with temperature, and the results indicated that the Langmuir isotherm fitted the experimental data well. Simulation results indicated that the ΔH0 values of as-grown, H2SO4-modified CNTs and H2SO4/KMnO4-modified CNTs were 4.83, 14.37 and 29.92 kJ/mol, respectively. Based on ΔH0, the adsorption of Cu2+ onto H2SO4/KMnO4-modified CNTs is suggested to proceed simultaneously by physisorption and chemisorption but that onto as-grown and H2SO4-modified CNTs may proceed only by physisorption.  相似文献   

5.
《分离科学与技术》2012,47(7):1067-1075
Granular activated carbon (GAC) was used as adsorbent in batch experiments for the removal of COD from Purified Terephthalic Acid (PTA) wastewater. The results showed that COD adsorption onto GAC follows pseudo-second-order rate kinetics and that both boundary-layer diffusion and intraparticle diffusion are likely involved in the rate-limiting mechanisms. The adsorption of PTA wastewater components (COD) onto GAC was found to be exothermic. ΔH° value is ?18.34 kJ/ mol indicating the complexity of the adsorption which is neither completely physical nor chemical in nature. The energetically heterogenic nature of the GAC surface was depicted by the variation in ΔHst,a with the surface loading.  相似文献   

6.
This study describes the equilibrium, kinetics, and thermodynamics of the palladium(II) (Pd(II)) adsorption onto poly(m‐aminobenzoic acid) (p‐mABA) chelating polymer. The p‐mABA was synthesized by the oxidation reaction of m‐aminobenzoic acid monomer with ammonium peroxydisulfate (APS). The synthesized p‐mABA chelating polymer was characterized by FTIR spectroscopy, gel permeation chromatography (GPC), thermal analysis, potentiometric titration, and scanning electron microscopy (SEM) analysis methods. The effects of the acidity, temperature, and initial Pd(II) concentration on the adsorption were examined by using batch adsorption technique. The optimum acidity for the Pd(II) adsorption was determined as pH 2. In the equilibrium studies, it was found that the Pd(II) adsorption capacity of the polymer was to be 24.21 mg/g and the adsorption data fitted better to the Langmuir isotherm than the Freundlich isotherm. The kinetics of the adsorption fitted to pseudo‐second‐order kinetic model. In the thermodynamic evaluation of the adsorption, the Δ values were calculated as ?16.98 and ?22.26 kJ/mol at 25–55°C temperatures. The enthalpy (ΔH°), entropy (ΔS°), and the activation energy (Ea) were found as 35.40 kJ/mol, 176.05 J/mol K, and 61.71 kJ/mol, respectively. The adsorption of Pd(II) ions onto p‐mABA was a spontaneous, endothermic, and chemical adsorption process which is governed by both ionic interaction and chelating mechanisms. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42533.  相似文献   

7.
A type of chelating resin crosslinking polystyrene‐supported 2,5‐dimercapto‐1,3,4‐thiodiazole (also called bismuththiol I, BMT), containing sulfur and nitrogen atoms, was prepared. The structure of PS‐BMT was confirmed by FTIR, elemental analysis, and X‐ray photoelectron spectroscopy (XPS). Adsorption of Pd(II), Pt(IV), and Au(III) was investigated. The capacity of PS‐BMT to adsorb Pd(II) and Pt(IV) was 0.190 and 0.033 mmol/g, respectively. The adsorption dynamics of Pd(II) showed that adsorption was controlled by liquid film diffusion and that the apparent activation energy, Ea, was 32.67 kJ/mol. The Langmuir model was better than the Freundlich model in describing the isothermal process of Pd(II), and the ΔG, ΔH, and ΔS values calculated were ?0.33 kJ/mol, 26.29 kJ/mol, and 87.95 J mol?1 K?1, respectively. The mechanisms of adsorption of Pd(II), Pt(IV), and Au(III) were confirmed by XPS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 631–637, 2006  相似文献   

8.
Abstract

The powdered biomass of paddle cactus (Tacinga palmadora), a rustic plant of great occurrence in the driest regions of Brazil, was evaluated as a low-cost adsorbent to treat textile effluents containing crystal violet (CV) dye. The powdered paddle cactus (PPC) was mainly composed by lignin and holocellulose, as well as, a variety of functional groups. Best results for CV adsorption were found using an adsorbent dosage of 0.5?g L?1 at solution pH equivalent to 10.0. Fast adsorption kinetics was verified, being the equilibrium reached within 100?min, and the curves were well modeled by the pseudo-first-order model. The isotherms were well-represented by the Langmuir model. The maximum adsorption capacity was 228.74?mg g?1 at 328?K. The estimated thermodynamics parameters were ΔG0T?=?328K of –9.08?kJ mol?1, ΔH0 of 12.44?kJ mol?1, and ΔS0 of 0.065?kJ mol?1 K?1. In addition, PPC was able to treat a simulated textile effluent containing organic and inorganic compounds, reaching 93% of color removal efficiency. These findings show that powdered paddle cactus can be applied as potential low-cost adsorbent to treat textile effluents containing CV.  相似文献   

9.
《分离科学与技术》2012,47(12):1848-1859
Organic solvents such as ethanol, find a wide range of applications in fuel, pharmaceutical industries, food industries, and paint formulations, among others. The removal of Ag(I), Co(II), and Mn(II) ions in ethanol by cation exchange resin, Dowex 50W-x8, was investigated. The adsorption characteristics of metal ions onto Dowex 50W-x8 resin were described by Langmuir isotherms. The maximum sorption exchange capacities at 298 K were obtained as 47.4 mg g?1, 52.6 mg g?1, and 58.5 mg g?1 for Ag(I), Co(II), and Mn(II), respectively. The data was also fitted to Temkin and Dubinin-Radushkevich adsorption isotherm models to evaluate other adsorption properties. The ion exchange of silver, cobalt, and manganese on cation exchange resin followed pseudo-second-order kinetics, and the intraparticle diffusion was rate-determining step. The thermodynamic parameters indicated that the sorption of metal ions onto Dowex 50W-x8 resin was spontaneous (negative ΔG°) and endothermic in nature (positive ΔH°) implying that the adsorption capacity increased with increasing temperature. The resin can be regenerated by eluting metal ions with 3.0 mol L?1 HNO3 followed by washing it with 10 mL of Millipore water and 10 mL of 2.0 M NaOH, respectively. The proposed method was applied for metal ion removal in real ethanol samples.  相似文献   

10.
In this research, five different vegetable oils were oxidized at four different temperatures (373, 383, 393, and 403 K) under Rancimat test conditions. An increasing rate of oxidation could be observed as temperature increased. The natural logarithms of the kinetic rate constant (k value) varied linearly with respect to temperature, with the temperature coefficients (TCoeff) ranging from 6.95×10–2 to 7.40× 10–2 K–1 for the vegetable oils. On the basis of the Arrhenius equation and the activated complex theory, frequency factors (A), activation energies (Ea), Q10 numbers, activation enthalpies (ΔH++), and activation entropies (ΔS++) for oxidative stability of the vegetable oils were calculated. The A, Ea, Q10, ΔH++, and ΔS++ values for the vegetable oils ranged from 6.38×103 to 28.03×103 h–1, from 86.86 to 92.42 kJ/mol, from 2.08 to 2.18, from 83.64 to 89.20 kJ/mol, and from –116.66 to –104.35 J/mol K, respectively.  相似文献   

11.
A novel fast and efficient adsorbent based on lamellar compound namely CeO2/Mg–Fe layered double hydroxide composite has been designed for fluoride removal from water. In order to improve fluoride removal efficiency, non-thermal plasma (NTP) was used to modify the surface state of composites. The prepared composites were characterized by powder X-ray diffraction, thermogravimetric analysis and surface area analyzer. Adsorption equilibrium and kinetics of fluoride on NTP modified composites were investigated. Experimental results indicated that the adsorption capacity was enhanced with NTP surface modification. The maximum adsorption capacity has been found to be 38.7–60.4 mg/g. The kinetic data of adsorption were found to best fit the pseudo-second-order model, while the equilibrium data were found to be well described by Langmuir model. In order to understand the mechanism of adsorption, thermodynamic parameters such as ΔGθ, ΔSθ and Ea were calculated. After NTP treatment, the ΔSθ increased from − 34.7 J/mol·K to − 0.770 J/mol·K, the Ea decreased from 78.8 kJ/mol to 58.9 kJ/mol and the ΔGθ (25 °C) decreased from − 2.62 kJ/mol to − 3.14 kJ/mol. These values indicate that the fluoride adsorption on NTP modified composites was improved.  相似文献   

12.
This study investigates optimization of various competitive adsorption parameters for removal of Cd(II), Ni(II) and Pb(II) from aqueous solutions by commercial activated carbon (AC) using the Taguchi method. Adsorption parameters such as initial metal concentration of each metal ion (C0,i ), initial pH (pH0), adsorbent dosage (m) and contact time (t) in batch technique were studied to observe their effects on the total adsorption capacity of metals onto activated carbon (q tot ). The adsorbent dosage has been found to be the most significant parameter. Interactions between C0,Cd ×C0,Ni , C0,Cd ×C0,Pb and C0,Ni ×C0,Pb have been considered for simultaneous metal ions adsorption. The optimum condition for adsorption of metal ions were obtained with C0,i =100 mg L?1, pH0=7, m=2 g L?1 and t=80 min. Finally, experimental results showed that a multi-staged adsorptive treatment would be necessary to reach the minimal discharge standards of metal ions in the effluent.  相似文献   

13.
The two‐dimensional coordination polymer cadmium phosphate with the morphology of rectangle layers was prepared by solid‐state template reaction at room temperature, and was characterized by XRD, FTIR, and TEM techniques. The as‐synthesized sample is a layered cadmium phosphate material, in which the structure is poly (CdPO4?) anion framework with ammonium ions and water species residing in the space between the layers, and cadmium ions are coordinated by the phosphate oxygen atoms. This article also presents the adsorption of Pb(II) ions from aqueous solution on the as‐synthesized coordination polymer cadmium phosphate, and the results showed that this inorganic polymer adsorbent had good adsorption capacity. It could reach to the saturation adsorption capacity within an hour, and its excellent adsorption capacity for Pb(II) was 5.50 mmol/g when the initial solution concentration was 1.68 × 103 μg/mL at T = 278K. Moreover, the adsorption kinetics and adsorption isotherms were studied, it revealed that the adsorption kinetics can be modeled by pseudo second‐order rate equation wonderfully. The apparent activation energy (Ea), ΔG, ΔH, and ΔS were 3.16 kJ mol?1, ?13.97 kJ mol?1, ?11.84 kJ mol?1, and 7.66 J mol?1 K?1, respectively. And it was found that Langmuir equation could well interpret the adsorption of the as‐synthesized coordination polymer cadmium phosphate for Pb(II) ions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

14.
Fig sawdust was used as a precursor for the production of activated carbon by chemical activation with H3PO4. The developed Fig sawdust activated carbon (FSAC) was used as a biosorbent for the removal of Pb(II) from aqueous solution. Highest adsorption of Pb(II) (95.8%) was found at pH 4. Equilibrium data fitted very well with the Langmuir isotherm model. Maximum adsorption capacity was determined 80.645 mg g−1 at pH 4. Kinetic studies demonstrated that the adsorption followed a pseudo second order kinetics model. The negative value of ΔG° confirmed the feasibility and spontaneity of FSAC for Pb(II) adsorption.  相似文献   

15.
《分离科学与技术》2012,47(10):1463-1470
The present study deals with the removal of phosphates from aqueous solution using activated carbon developed from coir pith. Batch adsorption experiments were performed to delineate the effect of initial pH, contact time, adsorbent dose and temperature on the removal of phosphates by coir-pith activated carbon (CAC) (activated by H2SO4). The removal was found to be maximum in the pH range of 6–10. The kinetics of adsorption showed that the phosphate adsorption onto CAC was a gradual process with a quasi-equilibrium being attained in 3 h. The adsorption equilibrium data followed the Temkin isotherm. Thermodynamic parameters such as ΔG o , ΔH o , and ΔS o were evaluated by applying the Arrhenius and van't Hoff equations, and it was found that the adsorption of phosphate on CAC was spontaneous and endothermic.  相似文献   

16.
The emf of the cell: Pt|Na(Hg)|NaBr(m), w wt.% 2-propanol—water mixture|AgBr, Ag has been measured with w = 10, 30 and 50 at temperatures of 293.15, 303.15 and 313.15 K in the molality range of NaBr from 0.04 to 0.18 mol kg?1. From these data the standard emf of the cell has been obtained and by utilizing data from the literature for the E0 of Ag/AgBr electrode the standard potential of sodium amalgam electrode has been determined. Mean activity coefficients of NaBr and thermodynamic functions ΔG0t, ΔH0t and ΔS0t for transfer of NaBr from water to 2-propanol—water mixtures have also been calculated. Thermodynamic quantities of transfer have been compared to those for the HBr electrolyte.  相似文献   

17.
《Carbon》1986,24(2):217-223
Chemisorption of oxygen on Saran char was followed dynamically with a volumetric adsorption apparatus at O2 pressures of 6.5 × 103 Pa to 3.4 × 104 Pa and temperatures of 338 K to 408 K. Concurrent O2 physical adsorption was observed to follow the low pressure limit of Langmuir's adsorption isotherm, V = KP; K was found to fit an Arrhenius form with a heat of adsorption of −11.7 kJ/mol and a preexponential factor of 7.11 × 10−7 ml(STP)/Pa. Chemisorption data, corrected for physisorption and blank errors, can be linearized on ln(amount adsorbed) vs In(time) axes. Collision theory and the Freundlich isotherm are used to develop a kinetic model which is consistent with this logarithmic relationship and which is able to reduce all data at the same carbon burn-off to a single straight line on appropriate logarithmic axes. The applicability of this model implies that the Saran char surface is characterized by a continuous distribution of heterogeneous adsorption sites.  相似文献   

18.
BACKGROUND: Pb(II) is common in both waste‐waters and gas emissions. In developing countries, public health problems have been reported concerning Pb(II) pollution, so that stringent measures are required to deal with it. MAJOR RESULTS: The adsorption and desorption behaviour of Pb(II) has been investigated on a natural Chinese kaolin. Several factors, including initial concentration, pH, equilibration time, dosage and temperature correlated positively with Pb(II) adsorption. The Pb(II) adsorption capacity of natural kaolin was 165.117 mg g?1. A kinetic study shows that Pb(II) adsorption on purified kaolin equilibrates within 35 min. The enthalpy changes of Pb(II) adsorption on purified kaolin were 63.683, 20.488 and 21.371 kJ mol?1 with entropy changes 262.250, 112.210 and 105.120 J mol?1 K?1 for solutions containing 50, 100 and 200 mg L?1 Pb(II) respectively, indicating an endothermic and spontaneous adsorption process. The desorption of Pb(II) from kaolin was difficult with more than 85% Pb(II) removal. Based on X‐ray diffraction (XRD) analysis, the Pb(II) adsorption on natural and purified kaolin was attributed mainly to the magnesite component and complexation with the mineral surface. CONCLUSIONS: Natural kaolin exhibits a satisfactory performance for adsorption of Pb(II) from aqueous solution. The optimum conditions for adsorption were: ionic strength = 0.01 mol L?1; pH ≥ 7.2; dosage = 10 g L?1; temperature = 25 °C; duration ≥ 16 h (Ci = 80 mg L?1); and the optimum conditions for desorption were ionic strength = 0.1 mol L?1 and pH ≤ 5.0. Copyright © 2009 Society of Chemical Industry  相似文献   

19.
Ahmet Sar? 《Desalination》2009,249(1):260-316
The adsorption characteristics of Pb(II) and Cd(II) onto colemanite ore waste (CW) from aqueous solution were investigated as a function of pH, adsorbent dosage, contact time, and temperature. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models were applied to describe the adsorption isotherms. Langmuir model fitted the equilibrium data better than the Freundlich isotherm. The adsorption capacity of CW was found to be 33.6 mg/g and 29.7 mg/g for Pb(II) and Cd(II) ions, respectively. Analyte ions were desorbed from CW using both 1 M HCl and 1 M HNO3. The recovery for both metal ions was found to be higher than 95%. The mean adsorption energies evaluated using the D-R model indicated that the adsorption of Pb(II) and Cd(II) onto CW were taken place by chemisorption. The thermodynamic parameters (ΔGo, ΔHo and ΔSo) showed that the adsorption of both metal ions was feasible, spontaneous and exothermic at 20-50 °C. Adsorption mechanisms were also investigated using the pseudo-first-order and pseudo-second-order kinetic models. The kinetic results showed that the adsorption of Pb(II) and Cd(II) onto CW followed well pseudo-second order kinetics.  相似文献   

20.
《分离科学与技术》2012,47(14):2104-2112
The sorption behavior of lead ions on coconut coir has been investigated to decontaminate lead ions from aqueous solutions. Various physico-chemical parameters were optimized to simulate the best conditions in which this material can be used as an adsorbent. Maximum adsorption was observed at 0.0001 to 0.001 mol L?1 of acid solutions (HNO3, HCl and HClO4) using 0.4 g of adsorbent for 4.83 × 10?5 mol L?1 lead concentration in ten minutes equilibration time. The adsorption of lead was decreased with the increase in the concentrations of all the acids used. The kinetic data indicated an intraparticle diffusion process with sorption being pseudo-second order. The determined rate constant k2 was 8.8912 g mg?1 min?1. The adsorption data obeyed the Freundlich isotherm over the lead concentration range of 2.41 × 10?4 to 1.45 × 10?3 mol L?1. The characteristic Freundlich constants i.e., 1/n = 0.44 ± 0.02 and K = 0.184 ± 0.0096 m mol g?1 have been computed for the sorption system. The sorption mean free energy from the Dubinin-Radushkevich isotherm is 10.48 ± 0.72 kJ mol?1 indicating the ion-exchange mechanism of chemisorption. The uptake of lead increases with the rise in temperature (293–333 K). Thermodynamic quantities i.e., ΔG, ΔS, and ΔH have also been calculated for the system. The sorption process was found to be endothermic. The proposed procedure was successfully applied for the removal of lead from battery wastewater samples.  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