Prediction of Carbon BTEX Adsorption Capacity Using Field Monitoring Data

The need for predicting adsorption capacity for benzene, toluene, ethylbenzene, and xylenes (BTEX) onto granular-activated carbon (GAC) is a problem commonly associated with petroleum-spill remediation. In this study, monitoring data are compiled from operational records of ground-water pump and treat remediation sites where GAC adsorption is utilized as a primary treatment mechanism for BTEX. The monitoring data are reduced to adsorbed and equilibrium concentrations from which Freundlich isotherms and various linear and multivariate models are calibrated for prediction of BTEX capacity on GAC. The models are employed by themselves and with Ideal Adsorbed Solution Theory to predict capacity for total BTEX and benzene. Several models are selected based on prediction ability and are tested with independent data. Two simple models, a multivariate model and a Freundlich isotherm, are recommended. Complex empirical models and Ideal Adsorbed Solution Theory did not perform as well as the selected models and were rejected. From the Freundlich isotherm, new Freundlich constants are reported that describe adsorption of total BTEX on GAC from gasoline-contaminated ground water.     

Equilibrium and Kinetic Study on Reactive Dyes Adsorption by Palm Kernel Shell-Based Activated Carbon: In Single and Binary Systems

The adsorption of two reactive dyes, Reactive Black 5 and Reactive Red E, onto palm kernel shell-activated carbon (PKSAC) was studied. The effect of the presence of more than one dye in solution on the equilibrium and kinetics of adsorption was investigated. Equilibrium isotherm models were applied to describe the adsorption capacities of single and binary systems. Adsorption of reactive dyes for single system can be represented by the Freundlich and the Redlich-Peterson models. For binary system, the equilibrium was described successfully by the modified extended Freundlich model. Experimental data showed that competitive adsorption for active sites on the carbon surface resulted in a reduction in the overall uptake capacity of the reactive dyes. The rates of adsorption in single system were found to agree well with the pseudosecond-order kinetic model. Finally, the chemical oxygen demand (COD) of the treated reactive dye solutions from single and binary systems showed that a minimum of 4 g/L dosage of PKSAC was needed to reduce the COD to an acceptable level according to the Water Quality Guidelines and the Pollutant Fact Sheets Guidelines.     

Removal of Endosulfan from Water Using Wood Charcoal—Adsorption and Desorption

Endosulfan, one of the most widely used pesticides in various sectors including agriculture, has been reported posing a threat to the ecology as well as to the environment. Contamination of groundwater and surface water sources with various pesticides is well documented, and this problem is prominent, particularly in rural areas. In the present study, efforts are made to remove endosulfan from water using wood charcoal, a local and low cost adsorbent. It gave removal efficiency of more than 90%. Equilibrium time was found to be around 5?h. Wood charcoal showed an uptake capacity of 0.53?mg/g with initial endosulfan concentration in the range of 0.25–5?mg/L and 1.77?mg/g for the range of 2–50?mg/L. Langmuir isotherm gave a better prediction of adsorption capacity than the Freundlich. The Langmuir isotherm fit also gave a better correlation with the experimental data. In the desorption study carried out, 10% solutions of acetone, methanol, acetic acid, saturated EDTA solution, and distilled water were used as eluents. Ten percent methanol solution was found performing well with an adsorbent regeneration of more than 80% after four cycles of adsorption desorption. Desorption was found to follow a zero order equation in the case of 10% solutions of both acetone and methanol.     

Modeling Volatile Organic Compound Sorption in Activated Carbon. II: Multicomponent Equilibrium

A new approach is presented for modeling multicomponent volatile organic compound (VOC) sorption equilibrium in ultra- and supernanoporous activated carbons. The model uses “Dubinin–Astakhov thermal equation of equilibrium adsorption” (DA-TEEA) for single-component adsorption thermodynamics and “ideal/real adsorbed solution theories” (IAST/RAST) for the multicomponent mixing rules. Use of the Henry’s Law adsorption isotherm resolves the singularity of DA-TEEA at zero-coverage conditions. The introduced method predicts multicomponent adsorption equilibria of VOCs based on equilibrium data of only one similar component. Single and binary adsorption equilibria of acetone and benzene vapors in Kynol ACFC-5092-20 activated-carbon-fiber-cloth adsorbents are predicted with the presented models and compared with modeled and measured characterization data available in the literature. The Wilson model for nonideal binary solution mixtures is used to predict the activity coefficients needed in DA-TEEA/RAST. Modeled results are compared against measured characterization data. The selected Henry’s Law upper-bound pressure (HUBP) is found to be an important factor controlling the accuracy of the multicomponent equilibrium models. An optimum HUBP can generate highly accurate results from both DA-TEEA/IAST and DA-TEEA/RAST. The accuracy realized by applying this method to acetone–benzene mixtures is sufficient for engineering design and development purposes.     

Adsorption Equilibrium Modeling of Space Station Wastewaters

An adsorption equilibrium model was developed for predicting the total organic carbon (TOC) removal by the International Space Station water processor's multifiltration beds. Ideal adsorbed solution theory is used to describe the competitive interactions between fictive components (FCs) that make up the TOC. The FC physical properties were based on several identified compounds to represent the distribution adsorbing compounds in the wastewaters. The TOC isotherms were performed using the wastewaters on three absorbents (a coconut-based granular activated carbon, a coal-based granular activated carbon, and a polymeric-based resin), which are contained in the multifiltration beds. The isotherms were used to validate the model for all three adsorbents. The FCs were determined in such a way that they can describe the TOC concentration for multiple beds in series.     

Adsorption of Sulfur Dioxide on Activated Carbon from Oil-Palm Waste

Adsorption of sulfur dioxide (SO2) onto activated carbons prepared from oil-palm shells was investigated in this paper. Experimental results showed that the adsorption temperature and SO2 concentration significantly determined the amount of SO2 adsorbed and the equilibrium time. However, sample particle size had minimum effect on the equilibrium time. For a fixed SO2 concentration, the adsorption rate and adsorption kinetic parameters (activation energy and frequency factor) were obtained. A linearly proportional relationship between the Brunauer-Emmett-Teller surface area and the adsorptive capacity of the activated carbon from oil-palm shells was observed. An intraparticle Knudsen diffusion model based on a Freundlich isotherm was developed for predicting the amount of SO2 adsorbed and the SO2 concentration profile within the particle. Based on the estimated isotherm parameters and diffusion coefficients by experimental data fitting, this model could predict the amount adsorbed under different concentrations very well. However, this model was unsuitable for the activated carbon prepared from oil-palm shells by chemical activation because of the occurrence of chemisorption, which was related to the nature of the sample surface functional groups.     

Ion-exchange equilibria of Ni, Co, Mn and Mg with iminodiacetic acid chelating resin Amberlite IRC 748

A chelating ion-exchange resin, Amberlite IRC 748 which carries an iminodiacetate acid functional group has been investigated for its adsorption properties towards Ni, Co, Mn and Mg from aqueous solution. Experiments were conducted through batch adsorption by varying the resin volume at three different pH values. It was observed that the amount of metals adsorbed by the resin increased with increasing pH. The applicability of both the Langmuir and Freundlich isotherms were analyzed on the equilibrium data obtained. In all cases, the Langmuir isotherm shows an excellent fit to the experimental data while the Freundlich isotherm failed to predict the data at higher loadings. The resin exhibited high selectivity towards nickel (K = 58,000) and cobalt (K = 16,800), which can be easily separated from magnesium and manganese at pH 4 and 5. The obtained values of the equilibrium constant K (l/mol) matched the expected order of selectivity of this resin which is Ni > Co > Mn > Mg. The results also showed that the adsorption mechanisms of these metals onto the resin follow a combination of monolayer and multilayer adsorption.     

Adsorption of arsenate and arsenite from aqueous solutions by cerium-loaded cation exchange resin

The removal of arsenic from water and wastewater is obligatory.Resin is one of the most effective adsorbents for the removal of arsenic.In order to improve the adsorption capacity of resin,a new cerium-loaded cation exchange resin arsenic adsorbent was prepared by impregnating cerium into the cation exchange resin.Batch adsorption experiments under various conditions,such as time,temperature,pH and with coexisting ions were carried out to evaluate the adsorption characteristics of cerium-loaded resin in the removal of As(Ⅴ)and As(Ⅲ) from aqueous solutions.The results showed that the adsorption kinetics of As(Ⅴ)and As(Ⅲ)obeyed a pseudo second-order kinetic model and the adsorption rate constants were 0.3159 and 0.5215 g·mg-1 ·min-1 ,respectively.The adsorption of As(Ⅴ)followed the Freundlich adsorption isotherm model and the adsorption isotherm data for As(Ⅲ)fitted well to the Langmuir equation model.The adsorption capacities were 1.0278 mg/g for As(Ⅴ)and 2.5297 mg/g for As(Ⅲ).Both the adsorption of As(Ⅴ)and As(Ⅲ)were found to be pH sensitive and the optimum pH was found to be 5-6.Except for the phosphate ion,the coexisting anionics,such as nitrate,chlorate,sulphate and carbonate,showed no remarkable effect on As(Ⅴ)and As(Ⅲ)adsorption.The desorption and regeneration study showed that the adsorption capacity of Ce-loaded resin for As(Ⅴ)and As(Ⅲ)could be restored to 97.80%and 69.61%,respectively,using 0.5 mol/L sodium hydroxide solution.     

Adsorption and desorption properties of D151 resin for Ce(Ⅲ)

The present research is aimed at the development of D151 resin as an adsorbent that it can be used in the adsorption of Ce(Ⅲ) ions.The adsorption and desorption behaviors of Ce(Ⅲ) on D151 resin have been investigated by chemistry analysis.The influence of operational conditions such as contact time,initial concentration of Ce(Ⅲ),initial pH of solution and temperature on the adsorption of Ce(Ⅲ) had also been examined.The results show that the optimal adsorption condition of D151 for Ce(Ⅲ) was achieved at pH=6.50 in HAc-NaAc medium.The maximum uptake capacity of Ce(Ⅲ) was 392 mg/g resin at 298 K.The adsorption of Ce(Ⅲ) followed both the Langmuir isotherm and Freundlich isotherm,and the correlation coefficients had been evaluated.Even kinetics on the adsorption of Ce(Ⅲ) had been studied.The adsorption rate constant k298 K valued was 1.3×10-5 s-1.The calculation data of thermodynamic parameters which ΔS0 value of 91.34 and ΔH0 value of 7.07 kJ/mol indicate the endothermic nature of the adsorption process.While,a decrease of Gibb’s free energy(ΔG0) with increasing temperature indicated the spontaneous nature of the adsorption process.Finally,Ce(Ⅲ) could be eluted by using 0.5 mol/L HCl solution and the elution percentage was as high as 100%.Adsorption mechanism was also proposed for the adsorption of Ce(Ⅲ) ions onto D151 resin using infrared spectroscopy technique.     

聚氨酯泡沫塑料对Au(Ⅲ)吸附热力学性能的研究

聚氨酯泡沫塑料吸附金被广泛应用于地质样品中微量金的分析检测,良好的吸附效果能够提高分析检测的准确性。运用静态吸附法研究了聚氨酯泡沫塑料吸附Au(Ⅲ)的热力学性能。研究表明:Au(Ⅲ)质量浓度为2. 0~70. 0 mg/L时,随着初始质量浓度增加,吸附量随之增加,且升高温度不利于吸附反应的进行;吸附更符合Freundlich吸附等温模型;经范特霍夫方程拟合,标准吸附焓变ΔH~θ为-42. 67 kJ/mol、标准吸附熵变ΔS~θ为-130. 6 J/(mol·K);实验温度下,聚氨酯泡沫塑料对Au(Ⅲ)的吸附过程(ΔG~θ<0)是自发进行的,以物理吸附为主,当温度升高到一定程度时,吸附过程无法自发进行。该研究对聚氨酯泡沫塑料富集金在地质样品检测中的条件优化和应用提供热力学数据支撑。     

Removal of Cr(VI) ions from aqueous solution using foundry waste material: Kinetic and equilibrium studies

Abstract

In the present paper, Cr(VI) ions removal from aqueous solutions by adsorption on waste mould (green) sand was investigated. Waste mould sand is byproduct of the grey iron foundry. Batch adsorption test was carried out to determine the removal characteristic for Cr(VI) ions from aqueous solution. The obtained results are promising in the use of waste mould sand as an efficient low cost and non-conventional adsorbent for the removal of Cr(VI) ions from aqueous solutions. The second order kinetics produced better fitting of results in terms of correlation coefficient which suggests that the adsorption kinetics of Cr(VI) ions on the waste mould sand followed the second order kinetic model. In the isotherm studies, Freundlich, Langmuir, Dubin–Radushevich and Redlich–Peterson isotherm models were applied and it was determined that the experimental data conformed to Langmuir isotherm model.

Dans cet article, on examine l’enlèvement d’ions Cr(VI) de solutions aqueuses par adsorption sur le sable (vert) à moulage résiduel. Le sable à moulage résiduel est un sous-produit de la fonderie de fonte grise. On a effectué un essai d’adsorption en discontinu afin de déterminer les caractéristiques d’enlèvement des ions Cr(VI) d’une solution aqueuse. Les résultats obtenus sont prometteurs quant à l’utilisation du sable à moulage résiduel comme adsorbant efficace non conventionnel et à faible coût pour l’enlèvement des ions Cr(VI) de solutions aqueuses. La cinétique de second ordre a produit un meilleur ajustement des résultats par rapport au coefficient de corrélation, ce qui suggère que la cinétique d’adsorption des ions Cr(VI) sur le sable à moulage résiduel suivait le modèle cinétique de second ordre. Dans les études d’isothermes, on a appliqué les modèles d’isotherme de Freundlich, Langmuir, Dubin, – Radushevich et Redlich – et de Peterson et l’on a déterminé que les données expérimentales se conformaient au modèle d’isotherme de Langmuir.     

D261大孔树脂吸附氰化物的性能及机理研究

研究了D261大孔树脂对氰化物的吸附性能及机理,考察了酸度、温度、溶液中氰化物质量浓度、时间及树脂用量对氰化物吸附的影响。试验结果表明,D261大孔树脂能有效地吸附简单氰化物和金、银、铜、锌、铁的氰络合物。热力学试验表明,吸附等温线符合Freundlich方程,吸附过程属于优惠吸附。动力学研究表明,吸附在室温下是瞬时反应,静态吸附过程主控步骤为Boyd液膜扩散,吸附的本质为物理吸附。同时,确定D261树脂的静态饱和吸附量为25.28mg/mL湿树脂。     

Derivation of a General Adsorption Isotherm Model

According to the thermodynamics of adsorption, a general equation for the adsorption isotherm was derived and verified by the literature data. The constants involved in the proposed model are physically defined. It was shown that the Langmuir and Freundlich equations were special cases of the proposed adsorption isotherm model. The proposed model indeed provides a good insight into the thermodynamic mechanisms of adsorption.     

Adsorption of globular proteins on locally planar surfaces: models for the effect of excluded surface area and aggregation of adsorbed protein on adsorption equilibria

Equilibrium statistical-thermodynamic models are presented for the surface adsorption of proteins modeled as regular convex hard particles. The adsorbed phase is treated as a two-dimensional fluid, and the chemical potential of adsorbed protein is obtained from scaled particle theory. Adsorption isotherms are calculated for nonassociating and self-associating adsorbing proteins. Area exclusion broadens adsorption isotherms relative to the Langmuir isotherm (negative cooperativity), whereas self-association steepens them (positive cooperativity). The calculated isotherm for adsorption of hard spheres using scaled particle theory for hard discs agrees well with that calculated from the hard disc virial expansion. As the cross section of the adsorbing protein in the plane of the surface becomes less discoidal, the apparent negative cooperativity manifested in the isotherm becomes more pronounced. The model is extended to the case of simultaneous adsorption of a tracer protein at low saturation and a competitor protein with a different size and/or shape at arbitrary fractional saturation. Area exclusion by competitor for tracer (and vice versa) is shown to substantially enhance the displacement of tracer by competitor and to qualitatively invalidate the standard interpretation of ligand competition experiments, according to which the fractional displacement of tracer by competitor is equal to the fractional saturation by competitor.     

Determination and Correlation of Binary Gas Adsorption Equilibria of VOCs

Highly porous activated carbon is used in the removal of volatile organic compounds (VOCs) and the purification of room air. Since the activated carbon must be capable of removing VOCs at low concentrations through adsorption, studies on the adsorption equilibrium of trace-level concentrations of VOCs are essential. To determine the adsorption isotherm, a headspace gas chromatography (HSGC) method was used, with analysis carried out using gas chromatography or gas chromatography-mass spectroscopy. The reliability of this method was confirmed by comparison of the adsorption isotherms of methanol measured by the HSGC method with those measured by the volumetric method. Isotherms for three different types of activated carbon and eight types of VOCs were determined over a wide range of concentrations. Furthermore, the results of the HSGC method for two systems of binary adsorption equilibria (dichloromethane+trichloroethylene) and (benzene+toluene), were found to be correlated with those of the ideal adsorbed solution theory.     

Viral hemorrhagic septicemia virus, Ichthyophonus hoferi, and other causes of morbidity in Pacific herring Clupea pallasi spawning in Prince William Sound, Alaska, USA

A recently proposed Jovanovic-Freundlich isotherm model for single component adsorption without lateral interactions on heterogeneous surfaces is extended to account for lateral interactions and for competitive adsorption. The model is tested using previously reported single component and competitive adsorption data of 2-phenylethanol and 3-phenylpropanol on ODS-silica with methanol-water as the mobile phase. A comparison is made regarding the ability of the Jovanovic-Freundlich and Langmuir-Freundlich models to predict competitive equilibria using the single component identified parameters. Fair predictions of the competitive data were obtained when using heterogeneous-surface models which do not take into account the possible interactions of phenylalcohols in the adsorbed phase via hydrogen bonding. Markedly improved predictions were obtained with models which account simultaneously for the two main sources of adsorbed phase nonideal behavior, i.e. adsorbate-adsorbate interactions and heterogeneity of the adsorbent surface.     

Application of Natural Clayey Soil as Adsorbent for the Removal of Copper from Wastewater

Use of clayey soil has been explored in the laboratory scale experiment as a low cost adsorbent for the removal of copper from wastewater. The influence of metal ion concentration, weight of adsorbent, stirring rates, influence of temperature, pH are also evaluated and the results are fitted using adsorption isotherm models. From the experimental results it is observed that almost 90–99% copper can be removed from the solution using clay at optimized pH 5.5. Langmuir adsorption isotherm, Freundlich isotherm and Tempkin isotherm model have been used to describe the distribution of copper between the liquid and solid phases in batch studies and it has been observed that Langmuir isotherm better represents the phenomenon. From the experimental results rate constant, activation energy, Gibbs free energy, enthalpy, and entropy of the reaction are calculated to determine the mechanism of the sorption process. Thomas, Adams-Bohart, and Yoon-Nelson models are applied to the experimental data to determine the characteristic parameters of the column for process design.     

Kinetics and equilibrium of Cu(II) adsorption onto chemically modified orange peel cellulose biosorbents

A series of orange peel cellulose biosorbents has been specifically prepared by different chemical modifications to understand the mechanism of copper adsorption from chloride solutions. The different biosorbents and raw orange peels were characterized using elemental analysis and Fourier transform infrared spectroscopy (FTIR). The acidic and basic sites and pH of zero charge were also determined. The influences of pH, contact time, initial copper concentration and solid/liquid ratio on copper removal were examined. The maximum adsorption capacity of copper was 1.22 mol/kg, using orange peel esterified by 0.6 mol/L citric acid at 80 °C after 0.1 mol/L NaOH saponification. A comparison of different isotherm models revealed that the combination of Langmuir and Freundlich (L–F) isotherm model fitted the experimental data best. Results indicate that the chemically modified orange peel cellulose can provide an efficient and cost-effective technology for eliminating copper from aqueous solution.     

Gold Adsorption by Activated Carbon and Resin

Activated carbon and resins readily adsorb gold from cyanide leach solutions. The main advantages of carbon are its high selectivity towards gold, its ease of elution and its large particle size. On the other hand, resins do not suffer from the problems of pore blocking by fine particles in the slurry and show superior adsorption kinetics and higher loading capacity for gold. In addition, when resins are used in the form of fibre-reinforced sheets, many of the problems associated with beads are overcome. The experimental results are shown to fit the homogeneous surface diffusion model with certain modifications when pore blocking occurs. The Fritz and Schluender isotherm is used to describe the equilibrium behaviour of adsorbed species. This reduces to the well-known Freunlich isotherm when only one component (eg. Gold) need be considered.