Ion exchange adsorption in countercurrent perforated-plate columns

Numerical and analytical approaches are used to develop a mathematical model for the ion exchange in a column with a fluidized ion exchanger bed sectioned by perforated plates. The model is tested for adequacy using the ion exchange adsorption of copper ions on a Lewatit S100 cation exchanger (Germany) and nickel ions on a KU-2-8 cation exchanger in countercurrent perforated-plate columns.     

Ternary adsorption kinetics of gases in activated carbon

Ternary adsorption kinetic experiments of ethane (light species), propane (intermediate species) and n-butane in activated carbon are collected under various concentration combinations, temperatures and particle sizes. The effects of these parameters on the ternary adsorption dynamics are investigated. All the experimental data are compared with the predictions by a multicomponent heterogeneous macropore, surface and micropore diffusion (HMSMD) model recently proposed by Hu and Do (AIChE J (1993) 39 1628) using only single-component equilibrium and mass transfer parameters. The model can accurately predict the adsorption rates of ethane, propane and n-butane, but a small error in the calculation of the adsorbed amount of propane at ternary equilibrium is observed.     

Multicomponent mass transfer in fixed-bed carbon adsorption columns

The technique based upon the constant pattern model was extended to evaluate mass transfer coefficients for multicomponent (binary) adsorption by carbons. The mass transfer coefficient of the lesser adsorbed component was essentially the same for both single component and binary systems. The mass transfer coefficient of the more strongly adsorbed component was significantly lower in the binary case, indicating interference between components. The mass transfer coefficients obtained were used in a computer simulation of fixed bed adsorption columns, and experimental data were successfully predicted.     

Dynamics of adsorption columns with bacterial growth outside adsorbents

The dynamics of adsorption columns with the presence of bacterial activity was studied analytically and experimentally. The bacterial activity results in the formation of growing microbial films outside adsorbents. Equations describing the interaction between adsorption and bacterial growth were formulated and algorithms for their solutions developed. Experiments relating to the removal of valeric acid from aqueous solutions with granular carbon in the presence of denitrifying bacteria were performed to substantiate the analysis.     

The performance of molecular sieve adsorption columns: non-isothermal systems

A simple theoretical model is used to calculate dimensionless breakthrough curves and the corresponding temperature profiles for a non-isothermal adsorption column, operating under constant pattern conditions. The model involves three parameters α, which measures the relative rates of heat and mass transfer, β, which is a heat capacity term and λ, which measures the degree of non-linearity of the equilibrium isotherm. The effects of these parameters on the form of the concentration and temperature profiles is investigated. Experimental breakthrough curves for the non-isothermal sorption of propylene, cis-2-butene and 1-butene from an inert carrier gas, in a column packed with 5A molecular sieve, are analyzed and interpreted. The heat and mass transfer coefficients, calculated from the experimental curves, are shown to be consistent with independently measured values and conclusions are drawn concerning the nature of the controlling resistances.     

Modeling multicomponent adsorption of monoclonal antibody charge variants in cation exchange columns

Transport models are developed for the adsorption of monoclonal antibody charge variants in cation exchange columns for two different matrices: UNOsphere S, which has a macroporous architecture, and Capto S, which contains charged dextran polymers grafted to an agarose matrix. The UNOsphere S protein adsorption kinetics is described by a macropore diffusion model with effective pore diffusivity D_e = 8.3 × 10^?8 cm²/s, which successfully predicts resolution of charge variants by frontal analysis at residence times, L/u, between 0.9 and 5.4 min. The Capto S adsorption kinetics is very fast for individual charge variants and for coadsorption of their mixtures, but is dramatically slower for sequential adsorption, when a more strongly bound variant displaces a more weakly bound one. A Maxwell‐Stefan model assuming single‐file diffusion predicts, in agreement with experiments, poor resolution of charge variants by frontal analysis even at long residence times as a result of highly hindered counterdiffusion. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2503–2511, 2012     

The adsorption of dyes onto chitin in fixed bed columns and batch adsorbers

Chitin has the ability to adsorb substantial quantities of dyestuffs from aqueous solutions. Consequently, it may be a useful adsorbent for effluent treatment from textile mills. The design procedures for batch and continuous fixed bed adsorption columns have been investigated for four dyestuffs, namely, CI Acid Blue 25 (Telon Blue Anl, Bayer), CI Acid Blue 158 (Neolan Blue 29, Ciba Geigy) CI Mordant Yellow 5 (Eriochrome Flavine A, Ciba Geigy), and CI Dirert Red 84 (Solophenyl Brown 3RL, Ciba Geigy). The main fixed bed system variables studied are bed height, dye flow rate, and chitin particle size, and these effects have been incorporated into a simplified design model.     

The performance of molecular sieve adsorption columns: systems with macropore diffusion control

Generalized saturation (adsorption) and regeneration (desorption) breakthrough curves are presented for molecular sieve adsorption columns operated isothermally under conditions of macropore diffusion control. The validity of the theory is confirmed by comparison of the theoretical and experimental breakthrough curves for sorption of C₃H₈ and 1-C₄H₈ in Davison 5 Å molecular sieve. For these systems kinetic and equilibrium data are available from gravimetric measurements and the theory is shown to provide a satisfactory a priori prediction of column performance.     

The performance of molecular sieve adsorption columns: systems with micropore diffusion control

Experimental saturation (adsorption) and regeneration (desorption) breakthrough curves are reported for a molecular sieve adsorption column operated isothermally under conditions of micropore diffusion control. For systems with a linear equilibrium isotherm, column performance may be adequately predicted from Rosen's theoretical analysis [9,10]. The form of the breakthrough curves is very sensitive to quite small deviations from linearity and, for systems which exhibit a favourable Langmuir type of isotherm, regeneration is much slower than saturation under comparable conditions. These effects can be quantitatively accounted for by the non-linear model of Garg and Ruthven [1,2]. Equilibrium constants and diffusivities calculated from the breakthrough curves show satisfactory agreement with the values obtained from gravimetric measurements.     

Modelling of packed bed adsorption columns for the separation of green tea catechins

Green tea is a rich source of catechins, which when purified have a high economic value as they can be used as a supplement in several products, to increase their health benefits. Catechins are regarded as desired components with several applications in a variety of areas such as foods, cosmetics and pharmaceuticals. A multicomponent sorption model has been developed for the separation of catechins from liquid tea streams, with macroporous resins in a packed bed column. Two commercially available food grade resins were considered: Amberlite XADHP and Diaion HP20. For the desorption step, two food grade solvents are used: water and ethanol. The adsorption and desorption behaviour is subsequently mathematically described with one-dimensional axial dispersed plug flow model that can accurately simulate the dynamics of the solvent swing sorption columns. The model parameters were regressed from experimental data. Five components are modelled in the competitive sorption: the main four catechins present in green tea and caffeine. The model was used for the process design and optimization for the recovery of catechins from green tea.     

Simplified fixed bed column model for adsorption of organic pollutants using tapered activated carbon columns

The dynamic adsorption of organic pollutants (an acid dye and para-chlorophenol) has been investigated via tapered column adsorbers using activated carbon. Equilibrium sorption isotherm experiments were determined to provide a crucial parameter, the saturation capacity (q_e) of each pollutant by F 400 carbon, for operating continuous adsorption columns. The Redlich–Peterson isotherm gave the best fit model to describe the sorption process of these organic pollutants onto F 400 carbon. Adsorption studies of organic pollutants have been carried out in novel tapered fixed bed columns using activated carbon. A series of columns with different tapered angles, from one to five degrees, have been used. Experimental data obtained from the breakthrough curves have been analysed using the Bed Depth Service Time (BDST) model in this paper. However, the conventional BDST model has not been applied to tapered beds before, as the linear velocity of adsorbate is changing along the column. Therefore, some modifications have been developed to the original model. The extended-modified BDST model has proved to be successful in correlating the bed height and service time for tapered column adsorption.     

Scale-up effects due to near-wall channelling in isothermal adsorption columns: on the limitations in the use of plug flow models

The influence of the near-wall channelling phenomenon on the scale-up effects of adsorption column is analysed numerically. The radial fluid velocity profile is approximated by using the extended Brinkman model. The broadening of breakthrough curves during a change in adsorption column diameter is predicted either from the two-dimensional model of non-linear, favorable adsorption with local fluid velocity included directly in the differential mass balance equation or from the plug flow model with the influence of the flow distribution involved in the value of the effective axial dispersion coefficient. The predicted scale-up parameters are compared with available experimental data. Under discussion are the operating conditions which make the scale-up effects due to near-wall channelling significant and possible improper application of the dispersed plug flow model.     

The simulation of binary adsorption in activated carbon columns using estimates of diffusional resistance within the carbon particles derived from batc

A computational procedure is presented for solving the set of coupled parabolic partial differential equations describing the simultaneous adsorption oOrthogonal collocation is used to solve for the first time the general form of these equations for simultaneous adsorption which include the effects ofSimulated results obtained from this model are compared with experimental data for the adsorption of mixtures of 2-butanol and t-amylalcohol. When     

Theoretical prediction of breakthrough curves for molecular sieve adsorption columns — II general isothermal solution for micropore diffusion control

Theoretical breakthrough curves for saturation and regeneration of a molecular sieve adsorption column are calculated from the solution of the appropriate diffusion equation for the case of micropore diffusion control. It is shown that with increasing non-linearity of the isotherm desorption becomes much slower than adsorption so that the regeneration cycle will generally be the limiting factor in column design. By comparing the breakthrough curves for saturation with the appropriate asymptotic solutions the conditions for validity of the ‘constant pattern’ approximation are obtained. Although restricted to lean gas mixtures containing only a single adsorbable component the analysis provides useful insight into column performance which should be of value in process design.