Étude comparative des modèles d’isothermes linéaires et non linéaires pour l’adsorption de colorants dans un système simple et binaire

Abstract

The aim of this study is to evaluate effectiveness of the adsorbent, which is in our case activated carbon prepared from the sawdust; grapes cores and apricots cores in order to remove or eliminate the diamond green B; acid red 151; acid orange 10; basic red 2 in simple and multi-constitute system. Adsorbent have been tested at their normal state and at their physical and chemical form to remove or eliminate dyes listed above, other comparison has been done by using other adsorbent that is the Activated Aldrich carbon. In the first stage each pollutant is present alone in the suspension then in the second stage in competition. In pure substances, several adsorption isotherms models are tested and adsorption energies were identified. The influence of competition is evaluated while being based on the competition factor aij, determined by the SRS model. In addition, the extended Langmuir isotherm model is applied to simulate results of the competitive adsorption. The preparation of the adsorbent has been done in specific conditions in order to ameliorate the adsorption capacity and get an optimal rate of elimination and thus maximum allowable adsorption capacity. In order to compare the adsorption of dye and to have a good understanding of the adsorption process, four linears Langmuir adsorption isotherm models; one linear Freundlich isotherm model; one nonlinear Langmuir isotherm model and one nonlinear Freundlich isotherm models were used to do a comparison between the experimental and calculated data. The use of theoretical or empirical equations is mandatory for the interpretation of isotherms for the assessment of their possible applicability. In this work, the three-parameters isotherm models has been studied, we mention the Sheindrof-Rebhun-Sheintuch and the extended Langmuir isotherm model which have been applied and tested for the multi-constituents adsorption. An attempt was done to do the linearization of the extended Langmuir isotherm model into three additional forms, various initials dyes concentrations were variables, some competitions were observed, adsorption energies were found less than those found in the simple system, which means the existence of competition between dyes. The identification of different parameters of the extended Langmuir isotherms such as the adsorption maximal capacity & adsorption quantity and different Langmuir equilibrium constants and the models equations has been identified. Second case was studied; where we used parameters obtained from simple system to solve the multi-component isotherm model; we have seen some convergence between dye uptake from the experimental and binary system. For the mixture, the adsorption capacity was governed by the linear and nonlinear Sheindrof-Rebhun-Sheintuch equation, which is a competitive model for the binary system derived from the Freundlich isotherm model. In this study we did not limited only to use parameters of the mono-aqueous solution which were found in the Freundlich isotherm model to solve the SRS equations as indicated in the previous studies but we did identify them also in binary system, where 3 cases were studied, adsorption intensities as well as adsorption energies were determined for various variation of the initial concentration. We concluded that the adsorption capacities found in binary system are lower than those found in the simple system, which means that the competition occurred to occupy the free available adsorbent sites. In order to verify the validities of these models and check the statistical aspect by taking into consideration values of coefficients of determination; P-Values and all other important errors functions such as Chi-square statistic, RMSE, APE and SSE were used.