Two-resistance mass transfer model for the adsorption of various dyestuffs onto chitin

The kinetics of the adsorption of various dyestuffs onto chitin have been studied. The dyestuffs used are Neoland Blue 2G, Eriochrome Flavine A, and Solophenyl Brown 3RL and a number of process variables were considered, such as adsorbent mass and dye concentration. The mass transfer model is based on the assumption of a pseudoirreversible isotherm and two resistances to mass transfer. These are external mass transfer and internal pore diffusion mass transfer. The rate of adsorption of dyestuffs onto chitin can thus be described by an external mass transfer coefficient and a pore diffusion coefficient. The external mass transfer coefficients are 5.0 × 10^?5, 5.0 × 10^?5, and 1.0 × 10^?5 m·s^?1 and the pore diffusivities are 3.0 × 10^?10 and 4.0 × 10^?11 m²·s^?1 for Neolan Blue 2G, Eriochrome Flavine A, and Solophenyl Brown 3RL, respectively.     

Adsorption of dyes onto bagasse pith using a solid diffusion model

The adsorption of four dyes (Basic Blue 69, Basic Red 22, Acid Blue 25, and Acid Red 114) onto bagasse pith has been studied using an agitated batch adsorber. The variables studied were initial dye concentration and pith mass. A mathematical model has been developed based on external mass transfer and solid-phase diffusion. The model has been used to generate theoretical concentration–time decay curves, and these results were adjusted to experimental data by a best fit approach. The external mass transfer coefficients are 2.0 × 10^?3, 1.5 × 10^?3, 8.0 × 10^?4, and 5.0 × 10^?4 cm s^?1 and the solid diffusivities are 1.1 × 10^?8, 1.0 × 10^?8, 6.0 × 10^?9, and 3.0 × 10^?9 cm² s^?1 for Basic Blue 69, Basic Red 22, Acid Blue 25, and Acid Red 114.     

Two resistance mass transport model for the adsorption of acid dye onto chitin in fixed beds

A mass transport model has been developed to predict theoretical breakthrough curves in fixed bed adsorbers. The model has been tested using experimental data obtained for the adsorption of Acid Blue 25 on chitin. The effective diffusivity can be determined for the adsorption process by best fitting experimental and theoretical breakthrough curves and was found to be 5.5 × 10^?6 cm² s^?1.     

The external mass transfer of basic and acidic dyes on wood

The parameters affecting the initial adsorption rates of Astrazone Blue dye (Basic Blue 69) on to wood have been studied. A simple model has been proposed to determine the external mass transfer coefficients and these have been compared with values obtained using a more complex procedure. The external mass transfer coefficient, β, has been shown to vary linearly with agitation and initial dye concentration using log-log coordinates; furthermore β is independent of particle size. The effect of temperature has been studied and the activation energy for the process is 44 ± 2 kJ mol^?1. Similar correlations were obtained for the adsorption of Telon Blue dye (Acid Blue 25) on wood. Using log-log correlations, the external mass transfer coefficient was found to vary with (rev min^?1)^0.14, C₀^?0.27; and a small dependence on particle size was also observed. The activation energy for the external mass transfer process was 25 ± 2 kJ mol^?1.     

Analysis of Heat and Mass Transfer during High-Temperature Drying of Pinus radiata

This article describes the analysis of heat and mass transfer coefficients for a single board of Pinus radiata (D. Don) timber over a range of high temperature and superheated steam drying conditions. The calculated heat transfer coefficients were in the range 20 to 60 W m^?2 K^?1. The mass transfer coefficients were of the order of 2 × 10^?8 to 3 × 10^?7 kg m^?2 s^?1, based on the vapor pressure difference, and of the order of 0.002 to 0.04 m s^?1 (expressed in terms of mass transfer velocity) based on vapor concentration difference between the surface of the board and the bulk drying medium.     

Kinetics and diffusion processes in colour removal from effluent using wood as an adsorbent

The rates of adsorption of a basic dye, Astrazone Blue, and an acidic dye, Telon Blue, on wood have been studied. The rate controlling step is mainly intraparticle diffusion, although a small resistance due to a boundary layer is experienced. The activation energies for the adsorption of Astrazone Blue and Telon Blue on wood are 16.8 kJ mol^?1 and 9.6 kJ mol^?1, respectively. The diffusion coefficients vary from 6×10^?13 cm² s^?1 to 18×10^?13 cm² s^?1 for Astrazone Blue at 18°C and from 3 × 10^?13 cm² s^?1 to 8 × 10^?13 cm² s^?1 for Telon Blue at 18°C. The variation in diffusivities is attributed to boundary layer effects.     

Separation of mercury and arsenic from produced water via hollow fiber contactor: Kinetic and mass transfer analysis

The separation of Hg(II) and As(V) from produced water by hollow fiber contactors was investigated. Two identical hollow fiber modules were employed. The first module was used for extraction, while the second module was used for stripping. The optimum conditions achieved were 14% (v/v) of Aliquat336, 0.07 M thiourea, volumetric flow rate of 100 mL/min for aqueous solution and 0.02 M HCl of stripping solution. At such conditions, the maximum extraction of Hg(II) and As(V) attained 100% and 78.78%, respectively. Concurrently, the maximum stripping of Hg(II) and As(V) reached 47.88% and 6.66%, respectively. The overall mass transfer coefficients of Hg(II) and As(V) extraction were 2.31×10^?6 and 1.15×10^?6m/s, while the Hg(II) and As(V) stripping exhibited the overall mass transfer coefficients of 8.37×10^?7 m/s and 9.05×10^?7 m/s, respectively. Mass transfer coefficients of the organic layer diffusion (k₀) had the most effect on the overall mass transfer coefficients.     

Study of the mechanism of pore diffusion in batch adsorption systems

In this study the film-pore diffusion model was applied to describe system transport kinetics of three basic dye-carbon systems, namely Basic Blue 69, Basic Red 22 and Basic Yellow 21. The mass transfer parameters evaluated were the external mass transfer coefficient k_f (cm s^?1) and the effective diffusivity D_eff (cm² s^?1). A single k_f value was sufficient to describe each dye system: these were 0.15 × 10^?2, 0.20 × 10^?2 and 0.50 × 10^?2 cm s^?1 for BB69, BR22 and BY21, respectively. The effective diffusivity was found to have values much larger than those of pore diffusivities calculated from liquid diffusivities and its value decreased with increasing initial dye concentration. This was attributed to the effect of surface diffusion, hence pore diffusivity was exchanged by the effective pore diffusivity in the model. The present model was solved by the exponential curve fit technique; results were expressed in the form of experimental and theoretical Sherwood Numbers compared in terms of the residual.     

Surface mass transfer processes using peat as an adsorbent for dyestuffs

The factors affecting the initial rate of Telon Blue (Acid) dye adsorption onto peat have been investigated. The surface mass transfer coefficients for the rate of dye removal from solution have been determined and correlated as the dimensionless mass transfer term Sh/Sc^0.33. The function Sh/Sc^0.33 has been correlated with respect to four variables, namely, agitation, initial dye concentration, peat particle size range and the temperature of the dye solution. The mass transfer term varies with T^5.5, d_p^0.13, c_o^?1.1 and R.P.M.^0.26; consequently temperature has the most pronounced effect on the mass transfer coefficient.     

Equilibrium Distribution Coefficients of Some Nitrate Impurities in Sodium Nitrate from Zone Refining

Abstract

The equilibrium distribution coefficients of 10 impurities (Li, K, Rb, Cs, Ag, TI, Mg, Ca, Sr, and Ba) in sodium nitrate were determined from the measured values of the effective distribution coefficients obtained by zone refining. The equilibrium distribution coefficients obtained are as follows: LiNO₃, 9.2 × 10^?2; KNO₃, 3.0 × 10^?1; RbNO₃, 2.2 × 10^?2; CsNO₃, 1.3 × 10^?3; AgNO₃, 7.8 × 10^?1; TlNO₃, 5.2 × 10^?1; Mg(NO₃)₂, 7.4 × 10^?2; Ca(NO₃)₂, 1.5 × 10^?2; Sr(NO₃)₂, 3.0 × 10^?2; and Ba(NO₃)₂, 2.1 × 10^?2. These values are in favorable agreement with those estimated from the phase diagrams and/or those calculated from the heat of solid solution.     

Analytical solution using a pore diffusion model for a pseudoirreversible isotherm for the adsorption of basic dye on silica

An analytical solution for a two resistance mass transfer model explaining the adsorption of Astrazone Blue dye (Basic Blue 69) onto Sorbsil silica has been developed. The model includes a film mass transfer coefficient, k_f1 = 80 × 10⁻⁶cm·s−1, and an internal effective diffusivity, D_eff = 18×10⁻⁹cm²·s⁻¹ which controls the internal mass transport processes based on a pore diffusion mechanism.     

Derivative cathodic stripping voltammetry in the simultaneous determination of three textile dyes in aqueous solutions

Reactive dyes, such as Procion Yellow, Procion Red, and Procion Blue, were simultaneously determined in aqueous ternary solutions using derivative cathodic stripping voltammetry following adsorption on a hanging mercury drop electrode. An electrochemical cell containing Britton–Robinson buffer solution at pH 8 was used as the supporting electrolyte. The following experimental conditions were established: ?0.100 V deposition potential, 80 s deposition time, 50 mV pulse amplitude, 50 mV s^?1 scan rate, and 0.40 mm² maximum mercury drop size. A linear response was observed over the 0.630 × 10^?3 to 1.050, 1.441 × 10^?3 to 1.572, and 0.198 to 1.570 mg l^?1 ranges for Procion Yellow, Procion Red, and Procion Blue respectively. The detection limits were 0.210 × 10^?3, 0.480 × 10^?3, and 0.066 mg l^?1 respectively, with a relative standard deviation (n = 3) of 1.22%. The accuracy of the method was evaluated by derivative spectrophotometry, certifying the results as a function of proximity. All results were similar, indicating that derivative cathodic stripping voltammetry may be efficiently applied for the simultaneous determination of textile dyes in aqueous ternary solutions.     

HYDRODYNAMICS AND GAS-LIQUID-SOLID INTERFACIAL PARAMETERS OF CO-CURRENT DOWNWARD TWO-PHASE FLOW IN TRICKLE-BED REACTORS†

Design of trickle-fixed bed reactors requires knowledge of the hydrodynamics of two-phase co-current downward flow through fixed porous catalytic media and interfacial parameters. Unfortunately, most of the published papers deal exclusively with the hydrodynamics of an air-water system and the determination of gas-liquid-solid interfacial parameters in highly ionic solutions. In this paper, we present some experimental results on the hydrodynamics, pressure drop, liquid holdup, different flow patterns, gas-liquid interfacial areas and liquid-side mass transfer coefficients for organic non-viscous and viscous liquids and liquid-solid mass transfer coefficients with different packings: glass beads (d_p = 1.16 × 10^?3 m and 4 × 10^?3 m), spherical catalyst (d_p = 2.4 × 10^?3 m) and glass Raschig rings (d_p = 6.48 × 10^?3 m). Comparison between our values and correlations in the literature will be discussed.     

Kinetics of removal of p-toluene sulphonic acid from concentrated solution by granular activated carbon

The removal of p-toluene sulphonic acid (p-TSA) from concentrated solution by granular activated carbon (GAC) was studied in batch experiments. The first order rate constant was found to be 5.5010 × 10^?5 s^?1 for a solution of 1000 mg dm^?3. In order to establish the rate limiting step the pore and film diffusion coefficients were calculated from the half time equations. Film diffusion was found to be rate limiting. The average value of the external mass transport rate constant was 2.91 × 10^?6 cm s^?1. The adsorption isotherm was adequately described by the Langmuir model and belongs to type ‘H’ of Giles' classification.     

Extraction of Tetrahydrofuran and Ethylene Dichloride Solvents from Aqueous Solutions by Pervaporation through Thin Film Composite PDMS Membranes

Thin film composite (TFC) hydrophobic PDMS membrane of 5 µm active layer thickness supported on Polyethersulfone (PES) ultraporous substrate was synthesized and thermally crosslinked for the pervaporation based extraction of organic solvents such as Tetrahydrofuran (THF) and Ethylenedichloride (EDC) for the first time. The study was extended to acetone, ethanol, t-butanol, Iso-butanol, and acetic acid. Membranes were characterized by SEM, TGA, XRD, and FTIR to study the surface and cross-sectional morphology, thermal stability, crystalline nature, and structural properties, respectively. High selectivities of 868, 72, and 31 were observed at organic feed concentrations of 0.68, 3.42, and 9.38 wt% in water with reasonable fluxes of 0.2, 0.16, and 0.31 kg m^?2 h^?1 for EDC, THF and acetone, respectively at a downstream vacuum of 0.5 mmHg. The estimated mass transfer coefficients (MTCs) were found to be 9.11 × 10^?6, 11.77 × 10^?6, and 10.73 × 10^?6 m s^?1 for THF, EDC, and acetone extraction, respectively. The membrane exhibited considerable feasibility for scale-up due to its composite nature with significant potential for extraction of volatile organic solvents present in low concentrations. A comparison with previous values reported in literature revealed higher selectivities for extraction of EDC, THF and acetone using the present membrane.     

Role of unburnt carbon in adsorption of dyes on fly ash

Various fly ash samples with different unburnt carbon contents were collected, characterised and tested for adsorption of basic dyes, Methylene Blue and Crystal Violet, in aqueous solution. It was found that unburnt carbon plays a major role in dye adsorption. The mineral matter of fly ash has little adsorption capacity and most of the adsorption capacity of fly ash can be attributed to the unburnt carbon. The fly ash with higher unburnt carbon content will have higher adsorption capacity. For the carbon‐free fly ash, adsorption capacities for Methylene Blue and Crystal Violet are only 2 × 10^?6 mol g^?1 and 1.0 × 10^?6 mol g^?1, respectively, while the adsorption capacities for Methylene Blue and Crystal Violet on carbon‐enriched fly ash are 1.2 × 10^?4 mol g^?1 and 1.0 × 10^?4 mol g^?1, respectively. A two‐site Langmuir adsorption model best describes the adsorption isotherm. Copyright © 2005 Society of Chemical Industry     

Non‐dispersive absorption of CO2 in parallel and cross‐flow membrane modules using EMISE

BACKGROUND: This paper reports an analysis of the mass transfer behaviour of CO₂ absorption in hollow fibre membrane modules in parallel and cross‐flow dispositions. The ionic liquid EMISE, 1‐ethyl‐3‐methylimidazolium ethylsulfate, is used to achieve a zero solvent emission process and the experimental results are compared with CO₂ permeation through the membrane, without solvent in the lumenside. RESULTS: Overall mass transfer coefficients K_{overall, CF} = (0.74 ± 0.02) × 10^?6 m s^?1 and K_{overall, PF} = (0.37 ± 0.018) × 10^?6 m s^?1 were obtained for cross‐flow and parallel flow, respectively. These values are one order of magnitude lower than the coefficient obtained in permeability experiments, K_{overall, PERM} = (6.16 ± 0.1) × 10^?6 m s^?1, indicating the influence of the absorption in the process. Including the specific surface and gas volume of each contactor in the analysis, a similar value of a first‐order kinetic rate constant, K_R = 2.7 × 10^?3 s^?1 is obtained, showing that the interfacial chemical reaction CO₂‐ionic liquid is the slow step in the absorption process. CONCLUSION: An interfacial chemical reaction rate constant K_R = 2.7 × 10^?3 s^?1, describes the behaviour of the CO₂ absorption in the ionic liquid EMISE using membrane contactors in parallel and cross‐flow dispositions. Copyright © 2012 Society of Chemical Industry     

The Effect of External Mass Transfer Resistance during Drying of Fermented Sausage

The drying mechanism of fermented sausages (sucuks) that were cylindrical rod shaped, 40 cm long and 4 cm diameter, during ripening under natural convection conditions at different temperatures (15 to 30°C) was examined. To simulate the experimental drying curves, three empirical models and a diffusional model assuming negligible external mass transfer resistance were evaluated. The drying rate curves of sucuk samples were also simulated taking into account the influence of the external mass transfer resistance. The equation was solved using the trial-and-error solution algorithm developed in this study and the mass transfer coefficient, k _c , and effective moisture diffusivity, D _eff , were simultaneously determined (1.44 × 10^?8 to 1.93 × 10^?8 m/s and 4.30 × 10^?10 to 6.85 × 10^?10 m²/s, respectively). The proposed model considering the effect of external resistance allowed the accurate simulation of the experimental drying data of sucuks at different temperatures.     

Kinetics of leaching of tunisian phosphate ore particles in dilute phosphoric acid solutions

Van der Sluis et al.'s model was used to determine the rate of the partial dissolution of a Tunisian phosphate rock with dilute phosphoric acid (1.5 mass% P₂O₅). When the temperature rises from 25 to 90°C, for a given particle size, the mass-transfer coefficients, k_L°, vary from 3 × 10^?3 to 8 × 10^?3 m ·s^?1. The corresponding diffusion coefficients, D, lies between 6 × 10^?7 and 27 × 10^?7 m²·s^?1. Activation energy is equal to 14 kJ·mol^?1 and values of k_L°, at 25°C, are in the range of 0.28 × 10^?3 and 4 × 10^?3 m·s^?1 when the agitation speed goes from 220 to 1030 rpm, showing that the leaching process is controlled by diffusion rather than by chemical reaction.     

Extraction rates of amino acids by an emulsion liquid membrane with tri-n-octylmethylammonium chloride

The extraction rates of amino acids from alkaline aqueous solution into an emulsion liquid membrane containing tri-n-octylmethylammonium chloride as a carrier and Paranox 100 as an emulsifier were measured using a stirred transfer cell. The effects of agitation speed (0·33–0·66 rev s⁻¹), amino acid concentrations (0·5–50 mol m⁻³) and temperature (10–45°C) on the extraction rates were examined. The results were analyzed by a double-film model. The mass transfer coefficients of amino acids (0·26–1·58×10⁻⁵ m s⁻¹) and their complexes (0·60–1·72×10⁻⁵ m s⁻¹) were found to correlate well with the hydrophobicities of the amino acids. It was found that the surfactant layer influenced the mass transfer processes of both amino acids in the aqueous film and their complexes in the organic film. The permeation of amino acids with a large hydrophobicity through the emulsion liquid membrane was promoted by both high distribution and larger mass transfer rates. © 1998 Society of Chemical Industry