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1.
This paper discusses the adsorption capacity of silica gel sludge for phenol removal from aqueous solution. Kinetic experiments showed that phenol adsorption was completed after 2 h. Adsorption isotherms were measured for phenol from aqueous solution onto silica gel sludge under various pHs and temperatures. Results showed that the adsorption capacities for phenol was increased as pH decreased from 6.5 to 2. Temperature also was found to affect the adsorption isotherm. As temperature increases from 30 to 50°C, the adsorption capacity increases. The adsorption equilibrium of phenol on silica gel sludge was described by the linear Freundlich and Langmuir models. Furthermore, results showed that the isotherm parameters fit both linearized Langmuir and Freundlich adsorption isotherms. The Freundlich and Langmuir parameters at optimum pH was found as K
f=2.89, 1/n=0.23 and K
d=22.0, q
m=7.98, respectively. Whereas, for those at optimum temperature it was observed as K
f=2.87, 1/n=0.16 and K
d=20.93, q
m=7.91, respectively. 相似文献
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西辽河流域沙土的氨氮解吸行为研究 总被引:1,自引:0,他引:1
采用小型回填式土柱淋溶实验方法研究了西辽河流域沙土的氨氮解吸行为。结果表明,西辽河流域沙土的氨氮解吸行为符合Langmuir和Freundlich解吸等温式;沙土氨氮解吸比率Dr在0.44~0.99之间,平均为0.75,解吸迟滞性指数TⅡ在0.05~0.65之间,平均为0.29,沙土对氨氮的解吸迟滞性较强,解吸可逆性较弱。被吸附的氨氮解吸淋失的环境风险较小;沙土氨氮解吸比率Dr与土壤有机质含量、粘粒含量和粗粘粒含量呈极显著负相关,影响程度顺序为:有机质含量>粗粘粒含量>粘粒含量;解吸分配系数k和解吸迟滞性指数与土壤有机质含量分别呈极显著和显著正相关,与粘粒含量和粗粘粒含量没有相关性;草地、农田和林地结构由于土壤有机质和团聚体含量较高,氨氮解吸迟滞性较强,氨氮流失的环境风险较小,沙荒地结构氨氮流失的环境风险较大。 相似文献
3.
A new and simple equation has been presented here for calculation of adsorption and desorption rate constants of Langmuir-Freundlich kinetic equation. The derivation of new equation is on the basis of extension and correction to the geometric method which has been presented by Kuan et al. [Kuan, W.-H., Lo, S.-L., Chang, C.M., Wang, M.K., 2000. A geometric approach to determine adsorption and desorption kinetic constants. Chemosphere 41, 1741-1747] for the kinetics of adsorption/desorption in aqueous solutions. The correction is to consider that the concentration of solute is not constant and changes as adsorption proceeds. The extension is that we applied Langmuir-Freundlich kinetic model instead of Langmuir kinetic model to consider the heterogeneity and therefore it is more applicable to the real systems. For solving Langmuir-Freundlich kinetic model, some geometric methods and also Taylor expansion were used and finally a simple and novel equation was derived (Eq. (20)) for calculation of adsorption rate constant. This new method was named "extended geometric method". The input data of the obtained equation can be simply derived from initial data of adsorption kinetics. Finally the adsorption of methyl orange onto granular activated carbon was carried out at dynamic and equilibrium conditions and the capabilities of extended geometric method were examined by the experimental data. 相似文献
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F. Boudrahem F. Aissani-Benissad H. Aït-Amar 《Journal of environmental management》2009,90(10):3031-3039
Lignocellulosic materials are good precursors for the production of activated carbon. In this work, coffee residue has been used as raw material in the preparation of powder activated carbon by the method of chemical activation with zinc chloride for the sorption of Pb(II) from dilute aqueous solutions.The influence of impregnation ratio (ZnCl2/coffee residue) on the physical and chemical properties of the prepared carbons was studied in order to optimize this parameter. The optimum experimental condition for preparing predominantly microporous activated carbons with high pore surface area (890 m2/g) and micropore volume (0.772 cm3/g) is an impregnation ratio of 100%. The developed activated carbon shows substantial capability to sorb lead(II) ions from aqueous solutions and for relative impregnation ratios of 75 and 100%, the maximum uptake is practically the same. Thus, 75% represents the optimal impregnation ratio.Batch experiments were conducted to study the effects of the main parameters such as contact time, initial concentration of Pb(II), solution pH, ionic strength and temperature. The maximum uptake of lead(II) at 25 °C was about 63 mg/g of adsorbent at pH 5.8, initial Pb(II) concentration of 10 mg/L, agitation speed of 200 rpm and ionic strength of 0.005 M. The kinetic data were fitted to the models of pseudo-first order and pseudo-second order, and follow closely the pseudo-second order model. Equilibrium sorption isotherms of Pb(II) were analyzed by the Langmuir, Freundlich and Temkin isotherm models. The Freundlich model gives a better fit than the others.Results from this study suggest that activated carbon produced from coffee residue is an effective adsorbent for the removal of lead from aqueous solutions and that ZnCl2 is a suitable activating agent for the preparation of high-porosity carbons. 相似文献
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Violeta Neagu Carmen Paduraru Ion Bunia Lavinia Tofan 《Journal of environmental management》2009,91(1):270-276
Two acrylic adsorbents with different morphological structures and bearing amidoethylenamine and thiol groups were obtained and used for platinum sorption from chloride solution by the batch method. Physico-chemical parameters that influence adsorption such as initial Pt(IV) concentration, stirring time, pH, and adsorbent amount were investigated. The thermodynamic parameters of Pt(IV) sorption on the synthesized adsorbent were also evaluated based on Langmuir and Freundlich isotherms. Thermodynamic parameters estimated from Langmuir constants indicated that the adsorption is spontaneous, exothermic and there is a disordered state at the molecular level. The models used to analyze the sorption rate led to the conclusion that the most important step in the sorption of Pt(IV) could be both particle diffusion and chemical reaction of [PtCl6]− with amine functional groups. Thus, both the ion exchange and complex formation mechanisms can occur via nitrogen atoms in the recovery of Pt(IV) on the studied adsorbent. 相似文献
8.
Biosorption of nickel(II) from aqueous solution by Aspergillus niger: Response surface methodology and isotherm study 总被引:1,自引:0,他引:1
In the present study, the effects of biosorbent Aspergillus niger dosage, initial solution pH and initial Ni(II) concentration on the uptake of Ni(II) by NaOH pretreated biomass of A. niger from aqueous solution were investigated. Batch experiments were carried out in order to model and optimize the biosorption process. The influence of three parameters on the uptake of Ni(II) was described using a response surface methodology (RSM) as well as Langmuir and Freundlich isotherm models. Optimum Ni(II) uptake of 4.82 mg Ni(II) g−1 biomass (70.30%) was achieved at pH 6.25, biomass dosage of 2.98 g L−1 and initial Ni(II) concentration of 30.00 mg L−1 Ni(II). Langmuir and Freundlich were able to describe the biosorption isotherm fairly well. However, prediction of Ni(II) biosorption using Langmuir and Freundlich isotherms was relatively poor in comparison with RSM approaches. The biosorption mechanism was also investigated by using Fourier transfer infrared (FT-IR) analysis of untreated, NaOH pretreated, and Ni(II) loaded A. niger biomass. 相似文献
9.
Fotoula E. Droulia Vaya Kati Constantinos N. Giannopolitis 《Journal of environmental science and health. Part. B》2013,48(5):404-410
Sorption of 3,4-dichloroaniline (3,4-DCA) on four typical Greek agricultural soils, with distinct texture, organic matter content and cation exchange capacities, was compared by using sorption isotherms and the parameters calculated from the fitted Freundlich equations. The sorption process of 3,4-DCA to the soil was completed within 48–72 h. The 3,4-DCA sorption on all soils was well described by the Freundlich equation and all sorption isotherms were of the L-type. The sandy clay loam soil with the highest organic matter content and a slightly acidic pH was the most sorptive, whereas the two other soil types, a high organic matter and neutral pH clay and a low organic matter and acidic loam, had an intermediate sorption capacity. A typical calcareous soil with low organic matter had the lowest sorption capacity which was only slightly higher than that of river sand. The 3,4-DCA sorption correlated best to soil organic matter content and not to clay content or cation exchange capacity, indicating the primary role of organic matter. The distribution coefficient (K d) decreased with increasing initial 3,4-DCA concentration and the reduction was most pronounced with the highly sorptive sandy clay loam soil, suggesting that the available sorption sites of the soils are not unlimited. Liming of the two acidic soils (the sandy clay loam and the loam) raised their pH (from 6.2 and 5.3, respectively) to 7.8 and reduced their sorption capacity by about 50 %, indicating that soil pH may be the second in importance factor (after organic matter) determining 3,4-DCA sorption. 相似文献
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《Journal of environmental science and health. Part. B》2012,47(11):906-914
AbstractWe investigated the adsorption of glyphosate onto five subtropical soils of Paraná and São Paulo states, Brazil, a region of intense agricultural activities, aiming at the determination of kinetic and isotherm adsorption parameters which enable the evaluation of the potential leaching of the herbicide. The adsorption was fast, being described by the pseudo-second order and intraparticle diffusion models, thus suggesting that mixed mechanisms are involved. The Oxisol containing the highest concentrations of metal oxides (209.5?g kg?1 Fe2O3 and 160.2?g kg?1 Al2O3) was the sample with the highest rate constant, indicating the adsorption sites are readily available. All the soils are rich in aluminum and iron oxides, explaining the Freundlich coefficients (KF) between 642 and 1360?mg1-1/n kg?1 L1/n, which are higher than most of the coefficients described for other soils around the world. The maximum desorption (15% of the adsorbed amount) was observed for the Oxisol. For the other soils, desorption ranged from 2 to 7%. These results suggest that the leaching of free glyphosate to nearby surface and groundwaters is unlikely unless excessive doses are used. The adsorption parameters are useful for managing the right doses applied to the crops, thus avoiding contamination of adjacent areas. 相似文献