چكيده به لاتين
Today, the tendency to use mineral adsorbents has increased due to its low cost for removal of the flue gas of fossil-fuel power plants. The main abjective of this work is to optimize the operating conditions of CO2 adsorption by montmorillonite adsorbent in a batch reactor and optimize sorbent to improve adsorption capacity. Structural characteristics of the adsorbent were studied using various techniques including FTIR, BET and XRD. Response surface methodology (RSM) was employed to optimization the adsorption operational conditions, and four factors of reactor temperature and pressure, respectively, in the range of 25-65 °C and 9-1 bar, acid concentration for activating the surface in the range of 2-6 mol/lit and weight percentage of the impregnated in surface (hydrazine hydrate or sodium hydroxide) in the range of 0-40 %w/w, as input variables and absorption capacity (mg/g) and absorption percentage were considered as responses. Optimum conditions were introduced at the point where the capacity and percentage of adsorption were maximally possible. For the adsorbent of montmorillonite, the optimum temperature and pressure values were 25 °C and 9 bar and the adsorption capacity is 100.67 mg.g-1, for the hydrazine-impregnated in montmorillonite, the optimum of temperature, pressure, acid concentration and wt% hydrazine for modification the surface, respectively, 25 °C , 8.99 bar, 4.03 mol/lit, and 16.23 %w/w and the adsorption capacity is 102.213 mg.g-1. Also, for the sodium hydroxide-impregnated in montmorillonite, the optimal conditions for the input variables were obtained at 64.97 °C, 1.00 bar, 5.92 mol/lit and 39.99 %w/w ,respectively, and the adsorption capacity is 105.583 mg.g-1. Furthermore, additional experiments were performed to examine the isotherm and kinetic models and the thermodynamic parameters of absorption. According to the values of R2, for the montmorillonite adsorbent and the modified sample with sodium hydroxide, the isotherm model respectively is in accordance with the D-R and Toth isotherm model, which shows the mechanism of adsorption by Gaussian energy distribution on a heterogeneous surface. For the montmorillonite adsorbent modified with hydrazine, the isotherm model is in accordance with the Hill isotherm model. Which indicates the equilibrium of the adsorbate bond with the adsorption sites and the interaction of the sites. The study of kinetic models based on R2 values showed that for the Montmorillonite sample, the second-order model and for the modified Montmorillonite samples with hydrazine and sodium hydroxide, Elovich kinetic model provides the best fiting with CO2 absorption data. In general, the CO2 bond in the modified montmorillonite seems to be more under the impression diffusion and the formation of chemical bonds in the particles.
