Di(2-ethylhexyl)phosphoric acid (D2EHPA) in acetone was supported on the Amberlite XAD-1180 polystyrene divinylbenzene copolymer resin. The use of XAD-1180 impregnated with D2EHPA for the extraction of bismuth(III) fr...Di(2-ethylhexyl)phosphoric acid (D2EHPA) in acetone was supported on the Amberlite XAD-1180 polystyrene divinylbenzene copolymer resin. The use of XAD-1180 impregnated with D2EHPA for the extraction of bismuth(III) from nitrate medium was carried out using batch technique. Various parameters affecting the uptake of this metal ion were described in the previous paper (Belkhouche and Didi, 2010) and the capacity of the impregnated resin for bismuth(III) was found to be 490.7 mg/g of resin. Effect of temperature on the values of distribution equilibrium was studied to evaluate the changes in standard thermodynamic quantities. A comparison of Langmuir forms I, II and Freundlich sorption isotherms was realized and the kinetic models applied to the adsorption rate data were evaluated for Lagergren first order, the pseudo second order and Morris–Weber models. From the results, the adsorption of Bi(III) onto D2EHPA/XAD-1180 resin shown the exothermic character and followed the Langmuir form II isotherm. Thus, the capacity of monolayer adsorption of Bi(III) was equal to 769.23 mg/g of resin. Both the Lagergren pseudo first order and film-diffusion models were found to best describe the experimental rate data.展开更多
Knowledge of the state of water balance of agro-food products is an essential step in drying or storage operations for preservation. Our study made it possible to determine the thermodynamic parameters which influence...Knowledge of the state of water balance of agro-food products is an essential step in drying or storage operations for preservation. Our study made it possible to determine the thermodynamic parameters which influence the storage conditions of fresh tomatoes grown in the south of Benin;and to predict its hygroscopic behavior during post-harvest storage. The desorption isotherms obtained at 40℃, 50℃ and 60℃, by the static gravimetric method using saturated saline solutions, are compared with those of the theoretical models of Brunauer, Emmet and Teller (BET), SMITH, PELEG and Guggenheim-Anderson-Boer (GAB). An adjustment of the experimental points, on the theoretical models, was made thanks to the numerical method which exploits the fminsearch algorithm under the MATLAB software, version R2018a. The GAB model at 50℃ faithfully reproduces the experimental desorption curves for water activities from 5.5% to 82.3%. The net isosteric heat of sorption was determined using the Clausius-Clapeyron equation, it increases when the degree of dehydration of the product increases. The applied isokinetic theory and enthalpy-entropy compensation are consistent.展开更多
文摘Di(2-ethylhexyl)phosphoric acid (D2EHPA) in acetone was supported on the Amberlite XAD-1180 polystyrene divinylbenzene copolymer resin. The use of XAD-1180 impregnated with D2EHPA for the extraction of bismuth(III) from nitrate medium was carried out using batch technique. Various parameters affecting the uptake of this metal ion were described in the previous paper (Belkhouche and Didi, 2010) and the capacity of the impregnated resin for bismuth(III) was found to be 490.7 mg/g of resin. Effect of temperature on the values of distribution equilibrium was studied to evaluate the changes in standard thermodynamic quantities. A comparison of Langmuir forms I, II and Freundlich sorption isotherms was realized and the kinetic models applied to the adsorption rate data were evaluated for Lagergren first order, the pseudo second order and Morris–Weber models. From the results, the adsorption of Bi(III) onto D2EHPA/XAD-1180 resin shown the exothermic character and followed the Langmuir form II isotherm. Thus, the capacity of monolayer adsorption of Bi(III) was equal to 769.23 mg/g of resin. Both the Lagergren pseudo first order and film-diffusion models were found to best describe the experimental rate data.
文摘Knowledge of the state of water balance of agro-food products is an essential step in drying or storage operations for preservation. Our study made it possible to determine the thermodynamic parameters which influence the storage conditions of fresh tomatoes grown in the south of Benin;and to predict its hygroscopic behavior during post-harvest storage. The desorption isotherms obtained at 40℃, 50℃ and 60℃, by the static gravimetric method using saturated saline solutions, are compared with those of the theoretical models of Brunauer, Emmet and Teller (BET), SMITH, PELEG and Guggenheim-Anderson-Boer (GAB). An adjustment of the experimental points, on the theoretical models, was made thanks to the numerical method which exploits the fminsearch algorithm under the MATLAB software, version R2018a. The GAB model at 50℃ faithfully reproduces the experimental desorption curves for water activities from 5.5% to 82.3%. The net isosteric heat of sorption was determined using the Clausius-Clapeyron equation, it increases when the degree of dehydration of the product increases. The applied isokinetic theory and enthalpy-entropy compensation are consistent.
