Kinetics and Thermodynamics of Adsorption of VB12 onto Mesoporous Carbon Coated with PMMA

Ordered mesoporous carbons CMK-3, CMK-1 coated with poly(methyl methacrylate)(PMMA)(CMK-3- PMMA and CMK-1-PMMA) and pristine mesoporous carbons CMK-3, CMK-1 were employed to adsorb vitamin B12(VB12) from water solution. Adsorption isotherm and kinetics of adsorption were investigated via batch experi- ments. It was found that the adsorption capacity of VB12 at 30, 40 and 50 °C can reach 688.2, 572.4 and 428.7 mg/g, respectively. The adsorption isotherm can be described by Langmuir model. The pseudo first- and second-order kinetic models were employed to fit the dynamic adsorption. It was found that the dynamic adsorption follows the pseudo second-order model. The thermodynamic equilibrium coefficients obtained at different temperatures were used to evaluate the thermodynamic constants ΔG0, ΔH0 and ΔS0. The negative value of Gibbs free energy, ΔG0 indicates that the adsorption occurred via a spontaneous process. The increase in the value of –ΔG0 with increasing temperature indicates that higher temperatures were favourable to the sorption process. The enthalpy values of ΔH040 kJ/mol(66.36 kJ/mol and 56.43 kJ/mol) for CMK-3-PMMA and CMK-1-PMMA confirm that chemisorption were involved in the adsorption process. This is consistent with the IR spectra and is another evidence for the formation of hydrogen bond between PMMA in the pore of CMK-3 and VB12.     

自溶液中的吸附 VII: 硅胶自环己烷中吸附醇,酮和酯

The adsorption isotherms of some monofunctional alcohols, ketones and esters from cyclohexane onto silica gel have been determined at 30`C and 10`C. The silica gel used bad a BET area of 417 m2/g and an average pore radius of 45A. The concentrations of free and associated hydroxyls on the silica gel were 1.4 and 4.1/100A^2 respectively. The adsorption order is cyclohexanol>n-octyl alcohol>cyclohexanone>methyl isobutyl ketone>n-propyl acetate=n-amyl acetate. The adsorption decreases with increasing temperature as normal. Except at very low concentrations, the isotherms can be represented by the Langmuir equation. The limiting adsorption, nms, on the silica gel does not accord with the stoichiometric ratio (1:1) between the free surface hydroxyl groups of the adsorbent and the adsorbate. In addition to surface conditions and the functional group of the adsorbate, it seems that the limiting adsorption is also controlled by the other factors, including temperature, solvent, and, sometimes the chain length of the adsorbate. The standard free energy (ΔG0) and standard enthalpy (ΔH0) of the adsorbates in adsorptien processes have been determined from the Langmuir parameters. The results indicate that the absolute value of ΔH0 is higher than that of ΔG0 (in other words, standard entropy ΔS0 is negative), as in the case of the adsorption of gases. Since there is practically no difference in ΔG0 or ΔH0 of adsorption between alcohols or esters, it is suggested that in dilute solution only the polar groups take part in adsorption, and the hydrocarben chains remain in solution during the adsorption process. For ketones, the absolute values of ΔG0 and ΔH0 are somewhat lower for methyl isobutyl ketone than that for cyclohexanone. A possible explanation is that in the adsorbed state the isobutyl chain of the methyl isobutyl ketone may somewhat close to the surface and thus decreases the adsorption and changes the ΔG0 and ΔH0.     

SINGLE AND BINARY ADSORPTION PERFORMANCE OF SALICYLIC ACID AND 5-SULFOSALICYLIC ACID ONTO HYPERCROSSLINKED POLYMERIC ADSORBENTS

Single and binary adsorption behaviors of salicylic acid and 5-sulfosalicylic acid onto hypercrosslinked polymeric adsorbents, i.e. NDA-101 and NDA-99 were investigated. The Freundlich model can successfully describe all the adsorption isotherms tested, which indicates a favorable and exothermic adsorption process. The adsorption of salicylic acid relies on π-π interaction, while the electrostatic interaction further influences the adsorption of 5-sulfosalicylic acid onto NDA-99. The adsorptive capacity of salicylic acid on NDA-99 decreases but increases on NDA-101 with 5-sulfosalicylic acid as the background component in a binary solute system. The amount of 5-sulfosalicylic acid adsorbed was decreased with the increase in initial concentration of salicylic acid on both adsorbents. The competition for the adsorption sites is considered to be predominant in the solid-to-liquid interaction process. The adsorption selectivity of salicylic acid onto NDA-101 is higher than onto NDA-99 by more than an order of magnitude. Thus, combination technique involving NDA-101 followed by NDA-99 can be effectively applied to separate and recover salicylic acid and 5-sulfosalicylic acid from wastewater.     

Separation and Purification of Glufosinate Through Combination of an Electrodialysis Membrane and a Macroporous Adsorption Resin

Glufosinate is a nonselective organophosphorus herbicide with low toxicity and high efficiency that is widely used in forestry, agriculture and other industries. In the process of manufacturing glufosinate, large amounts of ammonium chloride and coloured organic impurities are generated. Because of its high solubility in water, separation of glufosinate from inorganic salts is extremely difficult. Hence, a co-separation method combining an electrodialysis membrane and a macroporous adsorption resin was developed to obtain glufosinate with higlier purity. For the electrodialysis process, a glufosinate reaction solution was placed in a dilute chamber and desalinated. The concentration of inorganic salts in the resultant glufosinate aqueous solution was only 0.99 g/L under the optimal conditions of an operating voltage and a volume ratio of 9 V and 1:1, respectively. For the macroporous resin adsorption/desorption process, the sample solution treated by electrodialysis was pumped into the resin-filled column, which was eluted to obtain the eluent when the adsorption reached equilibrium. Consequently, nearly all the coloured organic impurities were removed under the optimal conditions, in which the resin type, pH value, flow rate, glufosinate concentration, temperature, ratio of ethanol and volume of eluent were LX-300C,3,0.5 mL·cm^2·min^-1,20 mg/mL,25℃, 50% and 400 mL, respectively. After the electrodialysis and adsorption/desorption process, the purity of the glufosinate was increased to 95.14%, and its recovery rate was as high as 98%. The advantages of this process included its ease of operation, environmental friendliness and low cost, which provided strong potential for its use in industrial applications.     

Measurement and theoretical analysis of the adsorption of supercritical methane on superactivated carbon

Adsorption/desorption isotherms of supercritical methane on superactivated carbon have been measured in the range of 0-10 MPa and 233-333 K (20 K interval). The reversibility of the physical adsorption process is acknowledged. The heat of adsorption of 16.5 kJ/mol is determined from the isotherms, and a new modeling strategy for isotherms with maximum is presented. The model yields fits to the experimental isotherms with precision of ?%, maintaining the constancy of the characteristic energy of adsorption. The exponent of the model equation expresses the pore size distribution feature of the adsorbent. The density of the supercritical adsor-bate is evaluated as a parameter of the model. It is shown that the conventional isotherm theory works too at supercritical condition if the limit state of supercritical adsorption is introduced into isotherm modeling.     

Study of preparation and adsorption properties of imidacloprid mesoporous surface molecularly imprinted polymerEI北大核心CSCD

Imidacloprid mesoporous surface molecularly imprinted polymer (MIP) was rapidly synthesized by one[1]step method, with imidacloprid as template molecule, methacrylic acid (MAA) as functional monomer, azodiisobutyronitrile (AIBN) as initiator and ethylene glycol dimethacrylate (EGDMA) as crosslinker. The characterization of MIP was completed by SEM, TEM, FT-IR, and nitrogen adsorption-desorption isotherms. The adsorption conditions were optimized. At the imidacloprid concentration of 100 µg/mL, MIP reached adsorption saturation and the adsorption time was shorter than that of the corresponding non-imprinted polymer (NIP), with the saturated adsorption value of 3.628 mg/g, and the imprinting factor of 1.27, indicating that the mesoporous structure and surface imprinting improved the mass transfer rate of imidacloprid in the adsorption process, so as to improving the adsorption capacity. In addition, under the same conditions, the adsorption capacity of MIP for imidacloprid was higher than acetamiprid, thiacloprid and thiamethoxam, indicating that MIP had better specific recognition ability. The imidacloprid mesoporous surface MIP can be prepared simply and rapidly, which may be a potential material in the field of sample pretreatment and rapid detection. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

PREPARATION AND CHARACTERIZATION OF NOVEL CHITOSAN DERIVATIVES: ADSORPTION EQUILIBRIUM OF IRON(Ⅲ) ION

The adsorption of Fe(Ⅲ)ions from aqueous solution by chitosan alpha-ketoglutaric acid(KCTS)and hydroxamated chitosan alpha-ketoglutaric acid(HKCTS)was studied in a batch adsorption system.Experiments were carried out as function of pH,temperature,agitation rate and concentration of Fe(Ⅲ)ions.The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and isotherm constants were determined.The Langmuir model agrees very well with experimental data.The pseudo-first-order and second-order kinetic models were used to describe the kinetic data and the rate constants were evaluated.The dynamical data fit well with the second-order kinetic model.The pseudo second-order kinetic model was indicated with the activation energy of 19.61 and 7.98 kJ/mol for KCTS and HKCTS,respectively.It is suggested that the overall rate of Fe(Ⅲ)adsorption is likely to be controlled by the chemical process.Results also showed that novel chitosan derivatives(KCTS and HKCTS)were favorable adsorbents.     

Kinetics and Thermodynamics of the Adsorption of Copper(Ⅱ) onto a New Fe-Si Adsorbent

A new kind of Fe-Si adsorbent was synthesized by iron oxide and diatomite after calcining and hydrothermal process. The influences of the initial Cu2+ concentration, p H and adsorption time on the Cu2+ removal efficiency were discussed. Three adsorption empirical kinetics equations and two thermodynamics equations were used to simulate the adsorption process. The microstructures of newly developed copper removal materials and properties of copper removal are characterized in details by SEM and EDS. Adsorption mechanism of the adsorbent was discussed. The suitable p H value for Cu2+ removal is 5.0 to 6.0 and the adsorption capacity increases with increasing the initial Cu2+ concentration. The adsorption kinetics of the adsorbent could be better described by pseudo second order kinetic model, whereas the adsorption isotherms highly conform to the Freundlich equation. The main crystalline phase of the adsorbent is Fe(Si O3) which can build porous structures conducive to the Cu2+ adsorption.     

Adsorption desulfurization of model gasoline by metal–organic framework Ni_3(BTC)_2

This work presented the synthesis of Ni-based metal-organic framework material with a paddle-wheel structure Ni_3(BTC)_2(Ni-BTC) and its application in thiophene(TP) adsorption from gasoline distillate by batch method. Adsorption isotherms of TP, cyclohexene, and toluene in cyclohexane onto Ni-BTC were conducted at 298–308 K to interpret the different effect of cyclohexene and toluene on TP adsorption.The results showed that, compared with cyclohexene, toluene addition in model gasoline led to a more evident decline in sulfur capacity of Ni-BTC, which is opposite to isostructural HKUST-1. The adsorption isotherms of TP, cyclohexene and toluene fit Langmuir model, S-type model and Temkin model well, respectively, indicating that the adsorption mechanisms of TP and the two competitors are different from one another. The adsorption capacities on Ni-BTC followed the order of cyclohexene toluene TP at the same equilibrium concentrations, implying the order of the adsorption affinities, which is in good agreement with the different extent of influence by the two competitors. The enthalpy of TP adsorption on Ni-BTC was estimated to be-80.01 kJ/mol, almost twice that on HKUST-1. The poor reusability of Ni-BTC in batch experiment, which is owing to its sensitivity to the air, can be prevented from regenerating used Ni-BTC in fixed-bed reactor by N_2 flow. The difference between Ni-BTC and HKUST-1 in maximum adsorption capacity(q_0), H of TP adsorption, and stability demonstrates that the central metal in isostructural MOFs plays a key role in adjusting the desulfurization performance, which may open up a potential avenue for the development of MOF-based adsorbents with superior desulfurization performance.     

Mesoporous V-doped TiO2 Nanoparticles as New Adsorbents for the Removal of Methylene Blue from Color Textile Wastewater

V-doped TiO2 nanoparticles(NPs) as dye adsorbents are synthesized by the co-precipitation method and characterized by X-ray powder diffraction, transmission electron microscope, N2 adsorption at 77 K, and X-ray photoelectron spectroscopy. The adsorption of methylene blue(MB) on the V-doped TiO2 NPs is studied in detail by varying the calcination temperature and V doping amount of the adsorbent, adsorbate concentration, adsorbent dosage, agitation rate, reaction temperature, and p H. The comparison of dye adsorption on V-doped TiO2 and parent TiO2 demonstrates that the adsorptive activity of TiO2 can be improved by V doping. The enhanced adsorptive performance can be attributed to the tremendous changes in texture, structure, and surface morphology of adsorbent. The adsorption kinetic analysis shows that the adsorption follows the pseudo-second order kinetics. The apparent activation energy for adsorption is calculated by Arrhenius formula to be 37.6 k J·mol-1, indicating that the adsorption is controlled by both of the diffusion and interfacial adsorption steps. The adsorption data are analyzed using Langmuir and Freundlich isotherms and the results indicate that the Langmuir model provides better correlation of the experimental data. The results conclusively show that the adsorption of MB is a spontaneous behavior and endothermic reaction with the ΔH value of 17.60 k J·mol-1.     

D301树脂对活性深蓝K-R的吸附性能

用D301树脂对活性深蓝K-R的吸附特征进行了研究.在所研究的温度和浓度范围内,用Freund lich方程能够很好地对吸附等温线进行拟合,吸附是吸热的优惠吸附过程.吸附焓、吸附自由能、吸附熵变的计算结果显示:△H>0,表明吸附是吸热过程;△G<0,表明吸附的自发性;△S>0,表明固/液界面上分子运动更为混乱.动力学研究表明,吸附过程受颗粒内扩散及其它扩散过程的共同控制.     

Zn(II)/α-FeOOH 吸附体系的固体浓度效应

采用宏观吸附-解吸实验系统地研究了Zn(II)在针铁矿(α-FeOOH)表面吸附的固体浓度(Cp)效应, 并考察了温度对固体浓度效应的影响, 揭示了固体浓度效应产生的机理. 实验结果表明: Zn(II)/α-FeOOH的吸附等温线随固体浓度的增加明显下移, 表现出显著的固体浓度效应; 随着固体浓度的升高, 平衡浓度相近的实验点的解吸滞后角(θ)和热力学不可逆系数(TII)均明显升高, 说明体系的可逆性随固体浓度的增大而显著降低, 这一结果符合亚稳平衡吸附(MEA)理论对固体浓度效应产生机制的预测. 本研究还发现Zn(II)/α-FeOOH体系在低温下的固体浓度效应比在高温下更为显著. 不同温度下的吸附-解吸实验表明,该体系的吸附可逆性随温度的升高而明显增强(θ和TII明显降低), 这再次证明了吸附可逆性对Cp效应的控制作用, 并从另一角度证实了MEA理论对固体浓度效应机制的解释. 实验测得Zn(II)/α-FeOOH体系的吸附热力学参数△H、△S分别为34.07 kJ·mol-1和195.71 J·mol-1·K-1, 表明Zn(II)可在针铁矿表面发生吸热的化学吸附反应.     

氨基萘酚磺酸在改性超高交联吸附树脂和弱碱树脂上的静态吸附行为比较

优选弱碱树脂ND 90 0和改性超高交联吸附树脂AL 8,比较研究两者吸附 1 氨基 2 萘酚 4 磺酸 (1,2 ,4 酸 )的静态吸附行为和吸附热力学特征 .两种树脂对 1,2 ,4 酸的吸附属于优惠的吸热吸附过程 .Langmuir和Freundlich两种等温方程都能够很好地描述ND 90 0对 1,2 ,4 酸的吸附等温线 ;仅Freundlich等温方程能很好地拟合AL 8的静态平衡吸附结果 .两种树脂对 1,2 ,4 酸的吸附自由能变均为负值 ,表明了吸附的自发性 ;吸附熵变均为正值 ,与“溶剂置换”现象有关 ;吸附焓变均为正值 ,主要是由于部分化学吸附的存在 .而ND 90 0的吸附焓变远远大于AL 8,表明前者以化学吸附为主、而后者以物理吸附为主的吸附机理 .     

Diffusion Mechanisms of Biosorption of Cr(VI) onto Powdered Cotton Stalk

The present study investigates biosorption diffusion mechanism for the removal of toxic hexavalent chromium from aqueous solution using powdered cotton stalk an agricultural waste biomass. The effects of pH, temperature, adsorption isotherms, adsorption kinetics, and thermodynamic on chromium biosorption were investigated. The results showed that a maximum removal efficiency of 95% was achieved at pH 2. The pH at zero point charge (pH_zpc) on biosorbent surface was 4.3. The adsorption kinetics showed that the pseudo-second order rate expression fitted well the biosrption process. The equilibrium isotherm was measured experimentally and results were analyzed by Langmuir, Freundlich, and Temkin isotherms using linearized correlation coefficients. The significant parameters for isotherms were determined. The Langmuir adsorption isotherm relative to two other isotherms was found to fit the equilibrium data best for chromium adsorption. Thermodynamic studies reveal that the biosorption of Cr(VI) on cotton stalk was endothermic, spontaneous and occurs with increase in disorder at solid-liquid interface. Adsorption diffusion kinetic was further analyzed and showed that biosorption mechanism was totally controlled by intraparticle diffusion mechanism.     

硅胶自环己烷中吸附含氧芳香化合物的研究

测定了15℃和30℃时硅胶自环己烷中吸附苯甲醇、苯甲醚、苯甲醛和苯甲酸的吸附等温线,这些等温线皆可用Langmuir公式表示。利用Langmuir常数n_m^s和b值计算了吸附过程的△G⁰、△H⁰和△S⁰;四种化合物的△S⁰皆为正值。测定了在较大复盖度时红外光谱图上硅胶表面自由羟基峰的移动值△v_OH。结果表明△H⁰和△v_OH及△v_OH^1/2间有线性关系。文中对所得结果做了初步的解释。     

Removal of Naphthol Green B from Aqueous Solution by Calcined Layered Double Hydroxides:Adsorption Property and Mechanism Studies

The adsorption of naphthol green B (NGB) by Mg/Al‐LDO (layered double oxides) with a Mg/Al molar ratio of 3:1 was investigated in a batch mode. Our study indicates that the maximum capacity of NGB adsorption at equilibrium is 193.4 mg and the percentage of absorption is 96.7%, with an adsorbent dose of 1.0 g/L under the following condition: 200 mg/L NGB concentration, temperature 298 K, pH 10.0 and an equilibrium time of 80 min. Langmuir and Freundlich adsorption models were used for fitting the isotherms, and the thermodynamic parameters have been calculated, which showed that the adsorption process was spontaneous and exothermic in nature. In the light of so called "memory effect", the Mg/Al‐LDO was found to recover their original layered structure after adsorption, and part of NGB ions intercalated into the interlayer of LDH (layered double hydroxides), which has been supported by XRD and FTIR. In addition, the competitive anions for adsorption and the regeneration of Mg/Al‐LDO have also been investigated.     

Mathematical modelling and simulation of adsorption processes at spherical microparticles.

A model for the adsorption process at spherical microparticles under transient diffusion conditions has been developed and solved using numerical simulation. This model allowed us to demonstrate that the system is controlled by two main dimensionless parameters: the adsorption rate constant ka' and the saturation parameter beta. Analytical models for the adsorption process at spherical microparticles under steady-state mass transport conditions have been derived. These models use previously developed empirical relationships for the calculation of the mass transfer coefficient (kc). The properties of the system were studied for both the case where mass transport is described by diffusion only and the case where it is the result of a coupled diffusion/convection process. These mathematical tools were then used to analyse the results obtained for the uptake of CuII by glassy carbon powder modified with the monomer L-cysteine methyl ester and to extract a minimum value for the adsorption rate constant which was found to be of the order of 10(-4) cm s(-1).     

Accurate correlation,structural interpretation,and thermochemistry of equilibrium adsorption isotherms of carbon dioxide in zeolite NaX by means of the GSTA model

Zeolite NaX (commonly known as zeolite 13X) has found wide use in industry for the separation of carbon dioxide from air, methane-containing landfill gas, and flue gases. Capture and sequestration of carbon dioxide has become of utmost importance to mitigate severe environmental problems associated to burning of fossil fuels, such as the greenhouse effect and the consequential warming of global climate. Due to its low energy consumption and ease of operation, the zeolite-13X molecular-sieve pressure-swing adsorption process has become the method of choice for the recovery and capture of carbon dioxide from air and flue gas. Accurate correlation of the equilibrium adsorption isotherms of carbon dioxide in zeolite NaX is required for the reliable modeling and simulation of that process. In this paper, we firstly show that none of the traditional adsorption isotherm models (such as those of Langmuir, Sips, Toth, UNILAN, and Dubinin–Astakhov) is entirely capable of correlating a published set of equilibrium adsorption isotherms of carbon dioxide in zeolite NaX that were measured over a range of eight decades of pressure. A generalized statistical thermodynamic adsorption (GSTA) model, which we had already derived and successfully applied to the adsorption of water vapor in zeolite 3A, is employed in this work to obtain a very accurate correlation of that set of adsorption isotherms of carbon dioxide in zeolite NaX, for the pressure range from 0.2 Pa to 6.4 MPa and in the temperature range from −78 to 150 °C. We also provide thermochemical and structural interpretations of the isotherms fit and make predictions for the isosteric heat of adsorption that are in excellent agreement with the available experimental data.