Adsorption separation of raffinose from sucrose by activated carbon: Equilibrium,kinetics and dynamic breakthrough

Separation of oligosaccharides with a varied number of monosaccharides is an important issue in food chemistry. Raffinose, a functional oligosaccharide, has attracted increasing attentions due to its strong proliferative effect on bacteria. Industrially, cottonseed meal is an important resource for producing raffinose; however, raffinose extracted from the cottonseed meal contains a significant amount of sucrose that debases raffinose’s quality. In this work, an adsorptive separation of raffinose and sucrose on activated carbon was reported. Adsorption isotherms, adsorption kinetics and dynamic column adsorption–desorption were investigated. The activated carbon chosen has a significantly higher adsorption capacity of raffinose (0.60~0.65 g/g) than sucrose (0.35~0.40 g/g) at the equilibrium concentration studied (~35 g/L) and temperature from 293 K to 333 K. Adsorption isotherms and kinetics were fitted by the Freundlich isotherm model and the pseudo-second-order model, respectively. The effect of flow-rate and initial feed concentration on dynamic adsorption were investigated; meanwhile, the separation performance was further confirmed from dynamic desorption using aqueous ethanol of 20% as eluant. Remarkably, raffinose with purity over 90% and recovery of 79.2% could be obtained by the adsorption–desorption cycle using an aqueous feed solution containing 20 g/L of raffinose and 6 g/L of sucrose.     

Adsorption and desorption of phenylalanine and tryptophane on a nonionic polymeric sorbent

Adsorption equilibrium of two amino acids — Phenylalanine (Phe) and Tryptophane (Trp) — onto nonionic polymeric sorbent, SP850 was studied under various pH values and temperatures. Adsorption equilibrium data of two amino acids on SP850 were fitted well with the Langmuir and Freundlich equations. Thermodynamic parameters such as Gibbs free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) were evaluated by applying the Van’t Hoff equation. Besides, adsorption kinetic of Phe was also investigated. Adsorption kinetic data were analyzed using the models of pseudo-first-order, pseudo-second-order and intraparticle diffusion. The results indicated that the pseudo-second-order model was more successful in simulating the adsorption kinetic data and the adsorption rate was mainly controlled by the diffusion rate in adsorption process. On the other hand, desorption studies were conducted by employing different organic solvents such as isopropyl alcohol (IPA), ethanol, and methanol. It was found that IPA was the best material for desorbing amino acid on the polymeric sorbent.     

Adsorption of phenols onto a polymeric sorbent

Adsorption of phenols from aqueous solutions onto a polymeric sorbent, SP206, was carried out in a finite batch adsorber. Multicomponent adsorption equilibrium data were experimentally measured and compared with those predicted by the ideal adsorbed solution theory (IAST) based on the Langmuir equation as single species isotherms. Intraparticle diffusion during adsorption was assumed to be expressed by the pore diffusion and the surface diffusion mechanisms and the effective diffusion coefficient of each species was determined by comparing experimental and predicted concentration histories. The surface diffusion model incorporated with the IAST successfully simulated the adsorption behaviour of a phenols-polymeric sorbent system up to three-species mixtures. The regeneration of spent sorbents was also investigated to get information for a cyclic adsorption process.     

大孔吸附树脂吸附乳酸及乳酸与谷氨酸的分离

通过筛选,得到大孔吸附树脂NKA-II,并用其对乳酸进行分离. 测定了该树脂对乳酸与谷氨酸的吸附选择系数,得到了乳酸在NKA-II上的吸附等温线,并对其吸附动力学和动态吸附进行了研究. 结果表明,NKA-II对乳酸和谷氨酸的吸附选择系数KGL=16.19. 该树脂对乳酸的吸附等温线符合Freundlich方程,在26和48℃下的相关系数R2均大于0.99,方程的特征参数n>1,属"优惠吸附". 吸附动力学研究表明,粒内扩散是吸附过程的主要控制步骤,符合Kannan-Sundaram粒内扩散模型,相关系数R2=0.9906,粒内扩散速率常数kp=6.0129 mg×min0.5/g. 动态吸附实验结果表明,乳酸的穿透体积比谷氨酸大110.6 mL,故该树脂可以成功地应用于乳酸与谷氨酸的分离.     

大孔吸附树脂对葡萄籽原花青素的吸附特性

从9种大孔吸附树脂中筛选出AB-8树脂对原花青素有较好的吸附和解吸性能。研究了原花青素在AB-8树脂上的吸附特性。静态吸附表明,吸附略有放热,平衡吸附时间为2 h,吸附行为更符合Langmuir等温式,用体积分数为50%的乙醇时解吸效果最好。当流速为1.5 BV/h时,动态泄漏吸附量比静态吸附量低15%,5BV可达到完全洗脱的目的,其原花青素的质量分数可达85.8%。     

A study of adsorption behavior of 2,4-Dichlorophenoxyacetic Acid onto various GACs

Adsorption and desorption of 2,4-dichlorophenoxyacetic acid (2,4-D) onto granular activated carbon (GAC) were studied to get basic information on their removal from aqueous solution. Single species adsorption equilibria of 2,4-D dissolved in water have been measured using F400, SLS103, and WWL. Equilibrium capacity increased with decreasing pH. The magnitude of adsorption capacity of 2,4-D was the order of F400> SLS103>WWL. Kinetic parameters were measured in a batch adsorber to analyze the adsorption rate of 2,4-D. The internal diffusion coefficients were determined by comparing the experimental concentration curve with that predicted from the surface diffusion model (SDM) and Pore diffusion model (PDM). The linear driving force approximation (LDFA) model was used to simulate isothermal adsorption behaviors in a fixed bed adsorber and successfully simulated experimental adsorption breakthrough behavior under various operation conditions. This paper is dedicated to Professor Dong Sup Doh on the occasion of his retirement from Korea University.     

Effect of complexing agents on liquid‐phase adsorption and desorption of copper(II) using chitosan

The effect of complexing agents on adsorption and desorption of Cu(II) from aqueous solutions using chitosan was investigated. Three complexing agents were used including EDTA (ethylenediaminetetraacetic acid), citric acid, and tartaric acid. It was shown that the isotherm data could be fitted by the Langmuir equation under a limited concentration range. Furthermore, the adsorption processes were analyzed by an intraparticle diffusion model and the rate parameters of intraparticle diffusion for Cu(II) adsorption could be correlated with the initial Cu(II) concentrations. Finally, the desorption of Cu(II) and its complexes from the loaded chitosan was tested using complexing agent solutions. Under comparable conditions, tartaric acid solution gave the best desorption efficiency. © 1999 Society of Chemical Industry     

Adsorption of 2,4-dichlorophenol from Aqueous Solution by a New Low-Cost Adsorbent – Activated Bamboo Charcoal

Adsorption experiments were conducted to study the removal of 2,4-dichlorophenol (2,4-DCP) from aqueous solution by a new low-cost adsorbent-activated bamboo charcoal. The results showed that acidic pH was favorable for the adsorption and removal of 2,4-DCP. Higher initial 2,4-DCP concentrations led to higher adsorption capacity. Most of the adsorption of 2,4-DCP occurred within the first 5 min, and about 90% of 2,4-DCP were removed from solution. After 5 min, the adsorption capacity increased slowly with contact time and the adsorption reached equilibrium in less than 100 min. As the adsorbent dose was increased, the removal of 2,4-DCP was increased, while the equilibrium time was slightly affected. Adsorption kinetics could be best described by the pseudo-second-order model, independent of adsorbent dosages. The adsorption behavior of 2,4-DCP onto bamboo charcoal fitted both Langmuir and Freundlich isotherms well, but followed Freundlich isotherm more precisely. This study demonstrated for the first time that activated bamboo charcoal could be used for the removal of 2,4-DCP in water treatment.     

AB-8大孔树脂对葡萄籽原花青素的吸附过程

研究葡萄籽原花青素粗提液在AB-8大孔树脂上的吸附过程,建立了AB-8大孔树脂吸附原花青素的相平衡方程和动态吸附模型,计算了不同流速、不同进料浓度下的总传质系数、传质区长度及穿透时间。实验结果表明,原花青素静态吸附符合Langmuir吸附等温方程式;AB-8树脂对原花青素的动态吸附属于外扩散控制过程;穿透时间计算值与实验值一致。建立的数学模型可用于指导实际生产操作,为吸附柱的设计提供参考。     

Adsorption of anionic textile dye Acid Green 9 from aqueous solution onto weak or strong base anion exchangers

The aim of this work is to study the thermodynamic and kinetic studies with regard to the adsorption of Acid Green 9 (AG9) on the most efficient resin, namely, acrylic weak base anion exchange resin with ethylenediamine‐functional groups (A1) selected from several anion exchange resins. The influence of the various experimental parameters such as, pH, initial dye concentration, contact time, temperature, and adsorbent dose was investigated by batch experiments. The extent of the dye adsorption increased with the decrease of the initial dye concentration and the increase of the contact time, temperature, and amount of the adsorbent. Adsorption process was quantitative and very fast at low concentrations of the dye. To investigate the mechanism of the adsorption and potential rate‐controlling steps, pseudo first‐ and second‐order, as well as intraparticle diffusion kinetic equations have been used. The adsorption kinetic of AG9 dye from aqueous solution onto A1 could be described by the pseudo second‐order reaction model. The obtained results are in agreement with the Langmuir and Freundlich models. In the optimum conditions established, an adsorption capacity of 500 mg textile dye (72% purity) g^?1 adsorbent (at 293 K) was reached. Desorption experiments by batch and dynamic methods were performed using a solution of 0.05 mol L^?1 NaOH. A series of 13 adsorption–desorption cycles were carried out by the dynamic method with a quantitative adsorption and the desorption efficiency higher than 95%. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Removal of chromium(VI) from aqueous solutions using polypyrrole-based magnetic composites

PPy/Fe₃O₄/AgCl composites were prepared via in situ polymerization for the removal of highly toxic Cr(VI). The structure and morphology of the prepared composites were characterized by the XRD, SEM, TEM, and VSM examinations. Up to 100 % removal was found with 1000 mg/L Cr(VI) aqueous solution at pH 2.0. The process of Cr(VI) ions’ adsorption was easy to reach equilibrium at higher temperatures. Adsorption results showed that Cr(VI) removal efficiency by the composites decreased with an increase in pH. Adsorption kinetics was described by the pseudo-second-order rate model. Isotherm data fitted well to the Langmuir isotherm model. Desorption experiment showed that the regenerated adsorption of PPy/Fe₃O₄/AgCl can be reused successfully for three times successive adsorption–desorption cycles without appreciable loss of its original capacity.     

Arsenic adsorption on goethite nanoparticles produced through hydrazine sulfate assisted synthesis method

Goethite nanoparticles synthesized using hydrazine sulfate as a modifying agent were evaluated for As(V) adsorption capacity. The nanoparticles were characterized for their morphological and structural features. The precipitated goethite particles were spherical with particle size of less than 10 nm. Batch adsorption study was carried out systematically varying parameters such as pH, contact time, initial As(V) concentration and adsorbent doses. The Langmuir isotherm represented the equilibrium data well and the estimated monolayer adsorption capacity at ambient temperature was 76 mg/g, which is significantly higher than most of the adsorbents reported in the literature. Adsorption kinetic data were better represented by the pseudo-second order kinetic model. Intra-particle diffusion played a significant role in the rate controlling process in the initial hour. Desorption study showed that the loaded adsorbent could be regenerated when treated with dilute sodium hydroxide solution of pH 13.     

螯合树脂对铜离子的吸附动力学和热力学

针对以谷氨酰胺-铜(II)配合物为供体酶法制备茶氨酸体系,研究了D401螯合树脂对Cu2+的吸附,探讨了吸附过程的热力学和动力学,通过红外光谱鉴定了树脂的配位结构. 结果表明,树脂吸附量随离子浓度和温度升高而增加,当pH为5.6时吸附量最大,达1.887 mmol/g. 不同温度下Langmuir方程均呈现很好的拟合度. 热力学平衡方程计算得DG<0, DH=21.5 kJ/mol, DS>0,表明该吸附过程是自发的、吸热、熵增加的过程. 动力学研究表明,该过程符合准二级动力学模型,吸附反应速率由颗粒扩散和液膜扩散共同控制. 该树脂在较宽的pH范围内对Cu2+具有很好的选择吸附性,可用于酶转化茶氨酸体系中Cu2+的去除.     

甲基橙印迹磁性壳聚糖聚合物的制备及吸附特性

以通过溶胶-凝胶法自制的Fe₃O₄@壳聚糖（CTS）微球为载体,甲基橙（MO）为模板分子,采用水溶液聚合法制得磁性壳聚糖表面分子印迹聚合物（MMIPs）。通过SEM、XRD、FT-IR和VSM表征了MMIPs的结构和性能,并探究了其对MO的识别与选择性吸附特性。研究表明：与非印迹聚合物（NIMPs,饱和吸附量为20.56 mg/g）相比,在相同条件（pH值6.5、25℃）下,MMIPs对MO具有明显的特异性吸附能力,在60 min左右吸附饱和,饱和吸附量（Q_e）可达113.16 mg/g;MMIPs对MO的吸附符合Langmuir等温吸附模型和准二级吸附动力学模型;在其他干扰染料的存在下,MMIPs的选择性系数（K）最高可达2.85,对MO具有选择识别性;此外,吸附完成后MMIPs可在磁场作用下快速分离,解吸附后循环使用5次,吸附率均在90%以上。     

Modelling high pressure extraction processes

Semibatch flow extraction of oil and other active ingredients from some plant materials (Silybum marianum, pepper, paprika and cocoa) with supercritical fluids (SCF) such as CO₂ and propane at different operating conditions was studied. Dynamic behaviour of the extraction runs was analysed by a mathematical model based on the adsorption–desorption equilibrium of extractable component from solid tissue, the diffusion of extractable component dissolved in SCF to the surface and mass transfer through the external film into the bulk. The linear driving force concept was employed to incorporate intraparticle diffusion as well as external mass transfer. Results show that the simplified model, which describes desorption process at equilibrium, could successfully describe cumulative rate data and is specially interesting for observation of the cross-over effect for adsorption–desorption, i.e. how desorption is changed with the increase of temperature at constant pressure.     

Adsorption of Divalent Cobalt from Aqueous Solution onto Chitosan–Coated Perlite Beads as Biosorbent

Abstract

Chitosan coated perlite beads are prepared by drop‐wise addition of a liquid slurry containing chitosan and perlite to an alkaline bath. The resulting beads are characterized using FTIR, SEM, EDXRF, and Surface area analysis and the chitosan content of the beads is 23% as determined by a pyrolysis method. Adsorption of Co (II) metal ions from aqueous solution on chitosan coated perlite beads is studied under both equilibrium and dynamic conditions. In the present investigation, a first order reversible rate equation is used to understand the kinetics of metal removal and to calculate the rate constants at different initial concentrations. The equilibrium characteristics of metal ion on newly developed biosorbent are studied and the experimental adsorption data are well fitted to Freundlich and Langmuir adsorption isotherm models and the model parameters are evaluated. The effect of pH, agitation time, concentration of adsorbate, and amount of adsorbent on the extent of the adsorption are investigated. The sorbent loaded with metal is regenerated with 0.10 mol dm^?3 sodium hydroxide solution. The adsorption desorption cycles indicated that the chitosan coated perlite could be regenerated and reused to remove Co (II) from waste water.     

Adsorption Characteristics of Sulfamethoxazole and Metronidazole on Activated Carbon

In this work, the removal of two pharmaceuticals i.e., an antibiotic drug, sulfamethoxazole and an antiparasitary drug, metronidazole onto activated carbon from aqueous solutions were studied. Batch adsorption studies were carried out at different pH, adsorbent concentrations, and temperatures. Adsorption isotherms have been modeled by Freundlich, Langmuir, and Dubinin-Raduskevitch (D-R) equations. The adsorption of these drugs was better represented by the Langmuir equation. The effect of the solution pH on the adsorbed amount of SM and MN was studied by varying the initial pH under constant process parameters at equilibrium conditions. The increase in pH of the solutions caused to decrease adsorption of SM and MN on AC. The kinetics of adsorption in view of three kinetic models, i.e., the first-order Lagergren model, the pseudo-second-order model, and the intraparticle diffusion model was discussed. The pseudo-second-order kinetic model describes the adsorption of both sulfamethoxazole and metronidazole on activated carbon. Rate constants for adsorption and desorption, and surface coverage have been evaluated with the help of another approach of the kinetic scheme. The effect of temperature was also studied at the range between 293 and 313 K. Thermodynamic parameters were calculated. The negative value of enthalpy change (ΔH°) indicated the exothermic nature of the adsorption process, and the negative values of free energy change (ΔG°) were indicative of spontaneity of the adsorption process. In this work adsorption behaviour of SM and MN on activated carbon was also evaluated by the data obtained from column experiments.     

Adsorption and desorption dynamics of amino acids in a nonionic polymeric sorbent XAD-16 column

A separation technique for amino acids, phenylalanine and tryptophan, from aqueous solution was studied in a column that was packed with a polymeric resin, XAD-16. This technique is based on a cyclic operation that has three typical steps such as adsorption, desorption, and washing. In particular, the desorption step for amino acids from the resin was carried out by using organic solvents, isopropyl alcohol and methanol. The desorption mechanism was assumed to be a competitive adsorption between amino acids and solvents, and the ideal adsorbed solution theory (IAST) based on the Langmuir equation as a single component isotherm was used in describing multicomponent equilibria. Adsorption and desorption breakthrough curves of the two amino acids were measured under various experimental conditions such as concentration, flow rate, and column length, in order to check the feasibility of the resin as a medium for the separation of amino acids. It was found that this separation technique could be a promising one for this purpose. Also, a simple dynamic model was formulated to describe both adsorption and desorption breakthrough curves of amino acids.     

Adsorption of organic amines from wastewater by carboxyl group‐modified polyacrylonitrile fibers

In this study, hexamethylenediamine (HMD) and hexamethyleneimine (HMI) were removed from a real wastewater by carboxyl group‐modified polyacrylonitrile (RPFC‐I) fibers. Adsorption of organic amines by fibrous absorbents is a new technique. Adsorption by fibers has advantages of fast kinetic, high adsorption capacity, and efficiency. Moreover, the fibers could be repeatedly used after regeneration. Batch adsorption tests were conducted to investigate adsorption comparison of the three fibers, adsorption kinetic, adsorption isotherms, regeneration, and readsorption stability. The experiments showed that RPFC‐I fibers had excellent adsorption capacity for HMI and HMD. The adsorption equilibrium was achieved very fast within about 5 min, and the removal rate of total nitrogen (TN) was above 99%. The adsorption kinetic could be well fitted by the pseudo‐second‐order equation. And the adsorption isotherm could be well fitted by the Langmuir model. The estimated maximum adsorption capacity was 105.2 mg g^?1, nearly similar with cation exchange capacity (CEC) of RPFC‐I fibers. Results from adsorption stability tests demonstrated that the RPFC‐I fibers could be fully regenerated by HCl and the regenerated fibers could be repeatedly used even after 12 adsorption–desorption cycles. Analyses from Fourier transform infrared and the adsorption tests suggested that chemical reaction between carboxyl groups and organic amines was the main mechanism for removal of HMI and HMD from the wastewater. The RPFC‐I fibers prepared in the current study have a wide application in wastewater treatment and useful substance recovery. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of pH on adsorption of 2,4-dinitrophenol onto an activated carbon

The adsorption characteristics of 2,4-dinitrophenol from water onto a granular activated carbon, F-400, were studied at pH 4.3, 7 and 10. Adsorption equilibria of 2,4-dinitrophenol on GAC could be represented by Sips equation. Equilibrium capacity increased with decreasing pH. The differences in the rates of adsorption are primarily attributable to the differences in the equilibrium at the various pHs. Intraparticle diffusion was explained by surface diffusion mechanism. An adsorption model based on the linear driving force approximation (LDFA) was used for simulating the adsorption behavior of 2,4-dinitrophenol in a fixed bed adsorber. Presented at the Int’l Symp. on Chem. Eng. (Cheju, Feb. 8-10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University.