The role of adsorbent pore size distribution in multicomponent adsorption on activated carbon (original) (raw)
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Polish Journal of Chemical Technology, 2017
The effect of textural and chemical properties such as: surface area, pore volume and chemical groups content of the granular activated carbon and monoliths on phenol adsorption in aqueous solutions was studied. Granular activated carbon and monolith samples were produced by chemical activation. They were characterized by using N2 adsorption at 77 K, CO2 adsorption at 273 K, Boehm Titrations and immersion calorimetry in phenol solutions. Microporous materials with different pore size distribution, surface area between 516 and 1685 m2 g−1 and pore volumes between 0.24 and 0.58 cm3 g−1 were obtained. Phenol adsorption capacity of the activated carbon materials increased with increasing BET surface area and pore volume, and is favored by their surface functional groups that act as electron donors. Phenol adsorption capacities are in ranged between 73.5 and 389.4 mg · g−1.
Asia-Pacific Journal of Chemical Engineering, 2019
The current study focuses on the single and multicomponent adsorption of phenolic compounds from solution on to an activated carbon in the concentration range of 50-500 ppm at room temperature. The observed adsorption isotherms were correlated using various predictive and non-predictive single and multicomponent adsorption isotherm equations. A strong influence of inter-adsorbate repulsion was evident based on the model proposed using Nitta's adsorption isotherm model.
Competitive adsorption and desorption of a bi-solute mixture: effect of activated carbon type
Adsorption, 2007
This study aims to clarify the effects of carbon activation type and physical form on the extent of adsorption capacity and desorption capacity of a bi-solute mixture of phenol and 2-chlorophenol (2-CP). For this purpose, two different PACs; thermally activated Norit SA4 and chemically activated Norit CA1, and their granular countertypes with similar physical characteristics, thermally activated Norit PKDA and chemically activated Norit CAgran, were used. The thermally activated carbons were better adsorbers for phenol and 2-CP compared with chemically activated carbons, but adsorption was more reversible in the latter case. 2-CP was adsorbed preferentially by each type of activated carbon, but adsorption of phenol was strongly suppressed in the presence of 2-CP. The simplified ideal adsorbed solution (SIAS) model underestimated the 2-CP loadings and overestimated the phenol loadings. However, the improved and modified forms of the SIAS model could better predict the competitive adsorption. The type of carbon activation was decisive in the application of these models. For each activated carbon type, phenol was desorbed more readily in the bi-solute case, but desorption of 2-CP was less compared with single-solute. This was attributed to higher energies of 2-CP adsorption.
Phenol removal by adsorption on granular activated carbon (GAC) was explored upto a range of 1000 mg/l in basal salt medium (BSM) commonly found in high strength industrial wastewaters. Six equilibrium isotherms models encountered in wastewater purification by adsorption studies were studied. Equilibrium data were fitted using non-linear regression technique. Based on the goodness of fit characterized by correlation coefficient and maximum deviation, a recommendation of model to be used in design equations was made. The kinetics studies and effect of concentration and adsorbent dose were also done. Equilibrium as well as kinetics studies were done in batch mode at normal pH and temperature of 30 0 C. The parameter values found in this study shall be useful in designing an activated carbon adsorber.
Water, Air, & Soil Pollution, 2000
Competitive adsorption of some priority pollutants, namely phenol, o-cresol, pnitrophenol, m-methoxyphenol, benzoic acid and salicylic acid from their aqueous solutions onto granular activated carbon (GAC) column was studied. Experiments were carried out to determine the breakthrough curves for adsorbates when present in aqueous solutions as single-, bi-and tri-solute system to evaluate the competitive adsorption phenomenon. Results indicate that in single-solute-GAC systems, p-nitrophenol is most strongly adsorbed as compared to other phenol derivatives studied. The substituted phenols were found to adsorb to a greater extent than phenol itself. The GAC-bisolute and GAC-trisolute systems clearly show the competitive or preferential adsorption of one solute over the other, as the solutes are competing for the available GAC surface for adsorption. Initially, all the adsorbates are taken up by the GAC surface, but near the breakthrough point the more adsorbable solute is able to desorb the less adsorbable one.
Heterogeneity of activated carbons based on adsorption of phenols from aqueous solutions
Zasoby Biblioteki Glownej Umcs, 2006
The heterogeneity of activated carbons (ACs) prepared from different precursors is investigated on the basis of adsorption isotherms of phenol and 2,3,4-trichlorophenol from dilute aqueous solutions at various pH values. The Langmuir-Freundlich equation as well as the Dubinin-Astakhov one have been used to estimate the parameters characterizing adsorption from aqueous phenol solutions on heterogeneous carbon surfaces. Adsorptionenergy distribution (AED) functions have been calculated by using an algorithm based on a regularization method. Analysis of these functions for activated carbons provides significant comparative information about their heterogeneity. Besides, literature data on enthalpy values for the transfer of phenol from a solution to surfaces of ACs confirm the correctness of the adsorption energies obtained in our study. The AED functions for phenol on activated carbons, generated by a utilization of the regularization method have been verified. As a verification tool, the Grand Canonical Monte Carlo simulation method carried out on a square lattice has been chosen.
Environmental Technology, 2011
Preparation of activated carbon from sewage sludge is a promising approach to produce cheap and efficient adsorbent for pollutants removal as well as to dispose of sewage sludge. The first objective of this study was to investigate the physical and chemical properties (BET surface area, ash and elemental content, surface functional groups by Boehm titration and weight loss by thermogravimetric analysis) of the sludge-based activated carbon (SBAC) so as to give a basic understanding of its structure and to compare to those of two commercial activated carbons, PICA S23 and F22. The second and main objective was to evaluate the performance of SBAC for single and competitive adsorption of four substituted phenols (p-nitrophenol, p-chlorophenol, p-hydroxy benzoic acid and phenol) from their aqueous solutions. The results indicated that, despite moderate micropore and mesopore surface areas, SBAC had remarkable adsorption capacity for phenols, though less than PICA carbons. Uptake of the phenolic compound was found to be dependent on both the porosity and surface chemistry of the carbons. Furthermore, the electronegativity and the hydrophobicity of the adsorbate have significant influence on the adsorption capacity. The Langmuir and Freundlich models were used for the mathematical description of the adsorption equilibrium for single-solute isotherms. Moreover, the Langmuir-Freundlich model gave satisfactory results for describing multicomponent system isotherms. The capacity of the studied activated carbons to adsorb phenols from a multi-solute system was in the following order: p-nitrophenol > p-chlorophenol > PHBA > phenol.
Predicting Solute Adsorption on Activated Carbon: Phenol
Langmuir, 2006
Activated carbon (AC), the most widely used adsorbent in water and in wastewater treatment, comprises a high surface area of very small, convoluted and interconnected pores. Despite the wide use of AC, there is little fundamental atomic-level understanding of its adsorption capacity and selectivity as well as its pore structure. The purpose of this work is to suggest the methodology for calculation of equilibrium adsorption capacity of common water organic pollutants and use it for phenol as a model. The effects of various functional groups, pore size, and coverage on thermodynamics of phenol adsorption from the gas phase and from water media are calculated using molecular mechanics (MM) and density functional theory (DFT) approaches. (24) Foresman, B.; Keith, T. A.; Wiberg, K. B.; Snoonian, J.; Frisch, M. J.
Analysis of some adsorption experiments with activated carbon
Chemical Engineering Science, 1976
A simple method is proposed whereby the film transfer coefficient and coefficient of diffusion in the particles may be determined from finite bath adsorption experiments. The method also makes it possible to separate pore and surface diffusion. Under certain conditions it is also possible to determine the influence of particle phase concentration on the surface diffusivity. The method is based on models describing the instationary diffusion in the solids. Data from six different adsorption systems were analysed using this method. The adsorbed components were: phenol, paranitrophenol, parachlorophenol, bensoic acid, phenylacetic acid and 24dichlorophenoxyacetic acid. In all systems surface diffusion was the determining transport mechanism in the particles. In the system phenol and phenylacetic acid the surface diffusion coefficient increased by about a factor 3 with an increase in surface concentration of about 40%. For parachlorophenol the increase was somewhat less. For the other systems there was no significant increase. The increase in diffusivity is explained by a decrease in bonding forces with increasing concentration.
Modeling of Fixed Bed Adsorption of Phenols on Granular Activated Carbon20191030 32560 1iwju04
Theoretical Foundations of Chemical Engineering, 2008
Mathematical modeling of liquid phase adsorption of phenols in fixed beds of granular activated carbon was investigated. The model considered the effects of axial diffusion in the fluid, the external film and internal diffusional mass transfer resistances of the particles, and the nonlinear adsorption isotherm of Freundlich. It was shown that the analysis of a complex multicomponent adsorption system could be simplified by converting it into a pseudo single-component adsorption system. This was achieved by lumping the concentrations of the components together as one single parameter, chemical oxygen demand. The resulting model equations were solved using the orthogonal collocation method and third-order semi-implicit Runge–Kutta method combined with a step-size adjustment strategy. Excellent agreement between simulated results and pilot plant data was obtained. Also, the breakthrough profiles revealed the formation of a primary monomolecular layer on the adsorbent surface.