Adsorption Isotherms for Methyl Tert-Butyl Ether and Other Fuel Oxygenates on Two Bituminous-Coal Activated Carbons

Methyl tert-butyl ether (MTBE) is frequently used as a gasoline additive to reduce carbon monoxide emissions from vehicles. Alternative fuel oxygenates are also used separately or in conjunction with MTBE including ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), diisopropyl ether (DIPE), tert-butyl alcohol (TBA), and ethanol (EtOH). Granular activated carbon (GAC) sorption is a proven technology for the removal of the ether oxygenates while the alcohols are not well adsorbed. In this research, Freundlich and Langmuir isotherms coefficients were developed based on linearized forms of the models for MTBE, ETBE, TAME, and DIPE (R2>0.97) on two common bituminous coal GACs:Calgon F400 and F600. No significant adsorption of either TBA or EtOH was observed on these carbons. The relative capacities on both Calgon F400 and F600 were DIPE>TAME>ETBE>MTBE>TBA, EtOH.     

Adsorptive removal of methylene blue by tea waste

The potentiality of tea waste for the adsorptive removal of methylene blue, a cationic dye, from aqueous solution was studied. Batch kinetics and isotherm studies were carried out under varying experimental conditions of contact time, initial methylene blue concentration, adsorbent dosage and pH. The nature of the possible adsorbent and methylene blue interactions was examined by the FTIR technique. The pH(pzc) of the adsorbent was estimated by titration method and a value of 4.3+/-0.2 was obtained. An adsorption-desorption study was carried out resulting the mechanism of adsorption was reversible and ion-exchange. Adsorption equilibrium of tea waste reached within 5h for methylene blue concentrations of 20-50mg/L. The sorption was analyzed using pseudo-first-order and pseudo-second order kinetic models and the sorption kinetics was found to follow a pseudo-second order kinetic model. The extent of the dye removal increased with increasing initial dye concentration. The equilibrium data in aqueous solutions were well represented by the Langmuir isotherm model. The adsorption capacity of methylene blue onto tea waste was found to be as high as 85.16mg/g, which is several folds higher than the adsorption capacity of a number of recently studied in the literature potential adsorbents. Tea waste appears as a very prospective adsorbent for the removal of methylene blue from aqueous solution.     

Sorption of SPADNS azo dye on polystyrene anion exchangers: Equilibrium and kinetic studies

The sorption of SPANDS from aqueous solution onto the macroporous polystyrene anion exchangers of weakly basic Amberlyst A-21 and strongly basic Amberlyst A-29 in a batch method was studied. The effect of initial dye concentration and phase contact time was considered to evaluate the sorption capacity of anion exchangers. Equilibrium data were attempted by various adsorption isotherms including the Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models. A comparison of kinetic models applied to the adsorption rate constants and equilibrium sorption capacities was made for the Lagergren first-order, pseudo second-order and Morris–Weber intraparticle diffusion kinetic models. The results showed that the adsorption isotherm is in the good agreement with the Langmuir equation and that the adsorption kinetics of SPADNS on both anion exchangers can be best described by the pseudo second-order model.     

STUDIES ON THE ADSORPTION OF FURFURAL FROM AQUEOUS SOLUTION ONTO LOW-COST BAGASSE FLY ASH

The present study deals with the sorptive removal of furfural from aqueous solution by carbon-rich bagasse fly ash (BFA). Batch studies were performed to evaluate the influence of various experimental parameters, namely, initial pH (pH₀), adsorbent dose, contact time, initial concentration, and temperature on the removal of furfural. Optimum conditions for furfural removal were found to be pH₀ ≈ 5.5, adsorbent dose ≈4 g/L of solution, and equilibrium time ≈4 h. The adsorption followed pseudo-second-order kinetics. The effective diffusion coefficient of furfural is of the order of 10^-13 m²/s. Equilibrium adsorption data on BFA was analyzed by Freundlich, Langmuir, Dubnin-Radushkevich, Redlich-Peterson, and Temkin isotherm equations using regression and error analysis. The Redlich-Peterson isotherm was found to best represent the data for furfural adsorption onto BFA. Adsorption of furfural on BFA is favorably influenced by a decrease in the temperature of the operation. Values of the change in entropy (ΔS⁰) and heat of adsorption (ΔH⁰) for furfural adsorption on BFA were negative. The high negative value of change in Gibbs free energy (ΔG⁰) indicates the feasible and spontaneous adsorption of furfural on BFA.     

Observations of moisture mass transfer rates in proteinate powders

Water vapour sorption and desorption are crucially important in the preservation of foods, in the manipulation of their textures and more widely in drying. Isotherms and rates of water vapour exchange in a series of protein substrates were measured under isothermal conditions. These substrates consistently displayed type II isotherms and revealed unusual vapour exchange rates for both sorption and desorption. This novel behaviour was observed consistently in dairy and soy proteins and in native proteins and thermally denatured proteins. The addition of a carbohydrate, such as sucrose, to the matrix resulted in type III isotherms and regular exchange rate behaviour. For the proteinates, moisture exchange rate coefficients and apparent diffusivities reached a maximum at a moisture concentration that was associated with the inflection point on the isotherm. This behaviour suggested multiple collisions of the water molecules with the partially hydrated surface in which the stickiness of the water molecules to the surface reached a minimum at the inflection point on the isotherm.