Adsorption of Naphthol Green B on unburned carbon: 2-and 3-parameter linear and non-linear equilibrium modelling

The study deals with adsorption of Naphthol Green B on two unburned carbons and the parent coal,from which the UCs have been created in a fluidised-bed power station.Particular attention has been paid to the adsorption equilibrium modelling:experimental data has been analysed using 2-parameter(Langmuir,Freundlich) and3-parameter(Redlich-Peterson) isotherms — both linear and non-linear regressions have been used for the estimation of the isotherm parameters.In the case of both UCs,the Langmuir isotherm model provides the worst fit,whereas 2-parameter Freundlich and 3-parameter Redlich-Peterson models are both good,from which 3-parameter Redlich-Peterson isotherm provides slightly better results(despite the penalty used for the higher number of parameters).In the case of both UCs,the linear regression of Freundlich and Redlich-Peterson models provides good results(comparable with non-linear regressions).Unlike both UCs,the best fit of the experimental data from the adsorption on the coal has been achieved by the Langmuir isotherm model.The results based on the Freundlich or Redlich-Peterson model were(in this case) somewhat worse.     

粉煤灰负载壳聚糖对磷吸附的热力学研究

以粉煤灰负载壳聚糖作为吸附剂,在静态吸附条件下,研究了其对磷的吸附行为,并对吸附过程的热力学进行了分析。结果表明,吸附平衡数据都能够较好地符合Langmuir和Freundlich吸附等温方程,但Langmuir方程能够更好地描述吸附等温线。在20～35℃范围内,磷在粉煤灰负载壳聚糖上的吸附是一个吸热过程,反应的吉布斯自由能变小,同时伴随着熵值的增加,吸附焓变为44.36 kJ/mol。     

氯苯酚在活性炭纤维上吸附平衡的研究

研究了水溶液中氯苯酚在活性炭纤维上的吸附平衡,实验探讨了反应温度、溶液pH值对活性炭纤维吸附平衡的影响。实验结果表明,平衡吸附量随着温度降低而升高;当pH值<7时,平衡吸附量几乎不随溶液的pH值而变化,而当pH值>7时,氯苯酚在活性炭纤维上的平衡吸附量随着pH值的增加而减小,pH值愈大,平衡吸附量减小的愈快。分别采用Langmuir模型和Freundlich模型描述吸附平衡等温线,在实验范围内Langmuir模型与实验数据吻合较好。     

Adsorption of humic acid onto chitin and chitosan

The adsorption of humic acid onto chitin and chitosan has been investigated. The uptake of humic acid from aqueous solution was determined from changes in concentration, as measured by ultraviolet-visible spectroscopy. The decrease in humic acid removal was observed with the increase in pH. A significant uptake of humic acid on both chitin and chitosan was observed. The uptake of humid acid on chitosan was greater than that on chitin. Adsorption isothermal data could be interpreted by the Langmuir and Freundlich equation. Langmuir and Freundlich constants have been determined. The experimental data of the adsorption equilibrium from humic acid solutions correlate well with the Langmuir isotherm equation, as compared to the Freundlich isotherm equation. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2305–2310, 1998     

Extraction and Adsorption Behavior of Co(II) on HTTA-Impregnated Polyurethane Foam

Abstract

The batch extraction of Co(II) from aqueous solutions with open cell polyethertype HTTA-loaded polyurethane (PU) foam has been studied using a radiotracer technique. The effect of pH, shaking time, and loading capacity has been investigated. The membrane properties of loaded PU foam sorbent offer unique advantage of adsorption. The fundamental studies of adsorption show that the classical Freundlich and Langmuir isotherms are followed in the entire concentration range of a 10^?5 to 10^?2 M solution of cobalt. The sorption mean free energy from the Dubinin-Radushkevich isotherm is found to be 13.8 kJ·mol^?1 and the loading capacity 4.44 mg·g^?1, suggesting that the ion-exchange or chemisorption mechanism operates. The kinetic parameters of adsorption also support a chemisorption mechanism and the first-order rate law. The rate constants and activation energies of sorption and desorption have been evaluated. The thermodynamic function of adsorption of ΔH, ΔS, ΔG, and equilibrium constant K _c have been calculated. The process of adsorption is established to be endothermic and chemisorption, stabilized through thermodynamic functions.     

农业废弃物香芋柄对含Mn2+废水的吸附

以废弃香芋柄作为新型生物吸附剂,通过静态吸附实验,研究了pH、温度、吸附时间、Mn2+初始浓度等因素对香芋柄吸附Mn2+的影响,分析了吸附过程的热力学、动力学和等温吸附规律. 结果表明,溶液初始pH=4,香芋柄用量6 g/L,30℃下吸附60 min,溶液中Mn2+吸附去除率达90.79%以上,吸附容量高达18.16 mg/g. 应用Langmuir和Freundlich模型描述香芋柄对Mn2+的吸附过程,结果显示Freundlich吸附等温线拟合效果更好. 吸附动力学实验数据符合准二级动力学模型. 计算得到热力学参数DG<0, DH>0, DS>0,表明该吸附过程是自发和吸热的过程.     

Adsorption of lactic acid onto three ionic liquid‐modified porous polymers

Three ionic liquid (IL)‐modified porous polymers were synthesized and used for the adsorption of lactic acid. The experimental adsorption kinetics and equilibrium data from the IL‐modified polymers were obtained. The kinetic study revealed a low temperature to be advantageous to the adsorption process. The dependence of the level of lactic acid adsorption on the amount of polymer, initial lactic acid concentration, and pH was examined at equilibrium. The maximum efficiency was obtained using the maximum adsorbent dose. A comparison of lactic acid adsorption at different pH revealed anion exchange to be the main interaction between the lactic acid and polymers, not molecular adsorption. The amounts adsorbed were fitted to the Langmuir, Freundlich, and Temkin equations. The equilibrium data for modified polymers (imidazole modified polymer, methylimidazole modified polymer, and ethylimidazole modified polymer) were best represented by the Langmuir and Freundlich isotherm with R² values of 0.99. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Adsorption of Nickel from aqueous solution by the use of low-cost adsorbents

The removal of Ni(II) from aqueous solution by different adsorbents was investigated. Calcined phosphate, red mud, and clarified sludge (a steel industry waste material) were used for the adsorption studies. The influence of pH, contact time, initial metal concentration, adsorbent nature and concentration on the selectivity and sensitivity of the removal process was investigated. The adsorption process was found to follow a first-order rate mechanism and rate constant was evaluated at 30 °C. Langmuir and Freundlich adsorption isotherms fit well in the experimental data and their constants were evaluated. The thermodynamic equilibrium constant and the Gibbs free energy were calculated for each system. The adsorption capacity (q _max ) calculated from Langmuir isotherm and the values of Gibbs free energy obtained showed that calcined phosphate has a higher capacity and affinity for the removal of Ni(II) compared to the other adsorbents used in the study.     

改性玉米芯吸附溶液中U(Ⅵ)的动力学和热力学

引言随着全球核能事业的不断发展,核燃料主要是铀的需求不断加大,在铀矿采冶过程中产生带有天然放射性核素如铀、钍、镭等放射性废水的量也在逐年增加,废水中的铀既有放射性,又有高的化学毒性,在环境中对人体健康和生态平衡造成严重威胁,世界各国高度重视铀矿采冶过程中产生的放射性废水处理技术的发展和应用。吸附法是一种很有潜力的方法,能克服传统方法的诸多不足,而经     

Electrochemical removal of boron from water: Adsorption and thermodynamic studies

The present work provides an electrochemical removal of boron from water and its kinetics, thermodynamics, isotherm using mild steel and stainless steel as anode and cathode respectively. The various operating parameters on the removal efficiency of boron were investigated, such as initial boron ion concentration, initial pH, current density and temperature. The results showed that the optimum removal efficiency of 93.2% was achieved at a current density of 0.2 A dm^?2 at pH of 7.0. First‐, second‐order rate equations, Elovich and Intraparticle models were applied to study adsorption kinetics. Adsorption isotherms of boron on Fe(OH)₃ were determined and correlated with isotherm equations such as Langmuir, Freundlich and D‐R models. Thermodynamic parameters, such as standard Gibb's free energy (ΔG°), standard enthalpy (ΔH°) and standard entropy (ΔS°), were also evaluated by Van't Hoff equation. The adsorption process follows second‐order kinetics. The adsorption of boron preferably fits with Langmuir adsorption isotherm suggesting monolayer coverage of adsorbed molecules. The adsorption of boron onto Fe(OH)₃ was found to be spontaneous and endothermic. © 2011 Canadian Society for Chemical Engineering     

Liquid Phase Adsorption of Phenol and Chloroform by Activated Charcoal

The adsorption equilibria of phenol and chloroform from aqueous solutions on four different particle sizes of activated charcoal were examined at different initial concentrations of the adsorbates. The experimental data were analyzed using the Langmuir and Freundlich isotherm models. Both models fit the adsorption data for phenol. The Freundlich model more accurately fits the adsorption data for chloroform than the Langmuir model. The sorption kinetics for phenol was studied using pseudo‐first‐order and second‐order kinetic models. The adsorption data better fit the second‐order model. The results of the study show that activated charcoal can be used as potential adsorbent for phenol and chloroform in drinking water.     

Kinetics and thermodynamics of U(Ⅵ) adsorption from aqueous solution by modified corncob

The corncob was microwave-assistedly modified by KMnO₄ and used for adsorption of U(Ⅵ)ions from aqueous solution.The kinetics and thermodynamics of their adsorption were measured using batch experiments.The results show that the kinetics of adsorption follows well the pseudo-second order equation,indicating that the uranium adsorption by the modified corncob is mainly chemisorption. The Langmuir,Freundlich and D-R isothermal adsorption models were used to relate the equilibrium data,finding that Langmuir isotherm of monolayer adsorption is better fitting them,pointing out that the adsorption mainly occurs on surface active sites of modified corncob.The values of apparent activation energy E_a and average adsorption energy E_s support also the suggestion that adsorption of U(Ⅵ) on modified corncob is mainly chemisorption,although some physical adsorption can not be got rid of.The thermodynamic parameters(ΔH,ΔS and ΔG)calculated from the adsorption isotherms at various temperatures indicated that the adsorption of U(Ⅵ)on modified corncob is an endothermic,spontaneous process and more favorable at higher temperature.     

Adsorption Characteristics of Congo Red from Aqueous Solution onto Tea Waste

The feasibility of using tea waste (TW) as a low-cost adsorbent for the adsorption of an anionic dye (Congo red) from aqueous solution has been investigated. Adsorption in a batch process was conducted to study the effect of adsorbent dosage, initial dye concentration, contact time, pH, and temperature. The experimental data were analyzed by the Langmuir, Freundlich, and Temkin models. The adsorption system was best described by the Langmuir isotherm (R ² > 0.99). Adsorption kinetics followed a pseudo-second-order model (R ² > 0.99). The effect of mechanical treatment (vibratory mill) was also studied. The experimental results showed that using this physical treatment leads to an increase in the adsorption capacity of TW from 32.26 to 43.48 mg/g. Thermodynamic analyses revealed that the adsorption of Congo red on TW was endothermic and spontaneous in nature. The results indicated that TW can be employed as a potential low-cost adsorbent for the removal of Congo red from aqueous solution.     

Comparison of adsorption equilibrium of glycyrrhizic acid and liquiritin on C18 column

The adsorption isotherms of glycyrrhizic acid (GA) and liquiritin (LQ) on a C₁₈ column were compared and the competitive adsorption of the two compounds was investigated. The experimental parameters in the equilibrium isotherms were estimated by linear and nonlinear regression analyses. The adsorption equilibrium data were correlated into the linear, Langmuir, competitive Langmuir, Freundlich, and Langmuir–Freundlich isotherm models. Over a moderate concentration range, the competitive Langmuir isotherm provided the best fit to the experimental data. The regression coefficients of the competitive Langmuir adsorption isotherms were 0.9754 and 0.9855 for the mixtures of GA and LQ, respectively. The coefficients obtained for the five isotherm models confirmed the superiority of the competitive Langmuir isotherm for analyzing the adsorption data of solutes.     

矸石基吸附剂对罗丹明B吸附特性的研究

采用静态吸附试验,研究了矸石基吸附剂对水中罗丹明B的吸附特性,考察了用量、吸附时间对罗丹明B吸附的影响。结果表明,矸石基吸附剂能有效地吸附水中的罗丹明B。利用Freundlich等温吸附方程和Langmuir等温吸附方程对其吸附过程进行描述,表明矸石基吸附剂易于吸附罗丹明B,吸附属于化学吸附,吸附过程是放热反应;修正准一级吸附动力学方程能很好地描述罗丹明B在矸石基吸附剂上的吸附;根据Arrhenius方程得出该吸附的经验活化能为45.25 kJ/mol。     

Optimised activation of bentonite for toluene adsorption

Acid-activation of bentonite was optimised to prepare an effective adsorbent of toluene. The activated bentonite was obtained with a specific surface area of 195 m²/g, a pore volume of about 0.46 cm³/g and a most frequent pore size of 62 Å. Compared to the raw bentonite, the adsorption of toluene onto acid-activated bentonite was increased from 66 mg/g to 197 mg/g. Vapor–solid adsorption isotherms of toluene were measured at 120 °C, 140 °C, 160 °C and 182 °C using an inverse gas chromatography. The experimental data were correlated with different adsorption isotherm models such as Langmuir, Freundlich, Langmuir–Freundlich and Toth models. Only the Langmuir–Freundlich equation provided good fit to the experimental data.     

Recycling flue gas desulphurization gypsum (FGDG) for removal of tetracycline from aqueous solutions

The present research aimed to explore the feasibility of removing tetracycline (TC) by flue gas desulphurization gypsum (FGDG). The adsorptive properties of FGDG for TC, such as pH values, adsorption isotherms and kinetics, and thermodynamics parameters, were investigated in the batch experiments. The results revealed that the process of TC adsorption was pH dependent and the optimal pH value was pH 8.0. The adsorption mechanism could attribute to the formation of TC-FGDG complexation. Langmuir isotherm model and the pseudo-second-order kinetic model can be described the better adsorption behaviors. The thermodynamics parameters indicated that adsorption process was endothermic and chemisorption in nature. FGDG would be an ideal adsorbent for removal of TC from aqueous solutions with the characteristics of low-cost and good adsorption properties.     

Analyzing the Adaption of Different Adsorption Models for Describing the Shale Gas Adsorption Law

The adsorption capacity of a shale gas reservoir is mainly determined by the isothermal adsorption experiment. In this study, the building conditions and performances of seven single‐component and five multi‐component adsorption models were compared and analyzed. The results show that most shale gas reservoir adsorption characteristics obey those of type I on the macroscopic scale. The adsorption isotherms of single components can be described by the Langmuir‐Freundlich, Langmuir, and Toth models. The revised Langmuir, extended Langmuir, and the loading ratio correlation (LRC) models can be applied to binary‐component mixtures; and the extended Langmuir and LRC models perform best for shale gas. The obtained results might have an important promoting effect for modeling the shortage of shale gas.     

Adsorption of malachite green onto bentonite: Equilibrium and kinetic studies and process design

The adsorption of malachite green onto bentonite in a batch adsorber has been studied. The effects of contact time, initial pH and initial dye concentration on the malachite green adsorption by the bentonite have been studied. Malachite green removal was seen to increase with increasing contact time until equilibrium and initial dye concentration, and the adsorption capacity of bentonite was independent of initial pH in the range 3–11. Four kinetic models, the pseudo first- and second-order equations, the Elovich equation and the intraparticle diffusion equation, were selected to follow the adsorption process. Kinetic parameters; rate constants, equilibrium adsorption capacities and correlation coefficients, for each kinetic equation were calculated and discussed. It was shown that the adsorption of malachite green onto bentonite could be described by the pseudo second-order equation. The experimental isotherm data were analyzed using the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich equations. Adsorption of malachite green onto bentonite followed the Langmuir isotherm. The thermodynamic parameters, such as ΔH, ΔS and ΔG, were also determined and evaluated. A single stage batch adsorber was designed for different adsorbent mass/treated effluent volume ratios using the Langmuir isotherm.     

The use of toxic solid waste for the adsorption of dyes from waste streams

The use of chromium‐containing toxic solid wastes from the leather industry for the removal of dyes from waste‐waters has been studied. A batch adsorption model has been employed and the role of various experimental parameters on the efficiency of the process evaluated. The extent of dye removal was studied by varying parameters such as pH, contact time, initial concentration of the dye and amount of adsorbent. The experimental equilibrium data for this system has been analyzed using the linearized forms of Langmuir and Freundlich isotherms. The Langmuir isotherm was found to provide the best theoretical correlation of the experimental data and the adsorption was found to follow pseudo‐second‐order kinetics. The dye adsorbed solid wastes were used for the preparation of pigments. In essence, this study provides a greener solution for chromium‐containing solid wastes, dye containing waste‐waters and dye‐adsorbed chromium solid wastes. Copyright © 2007 Society of Chemical Industry