Elaboration d’un composite poreux à base de la kaolinite et des coquilles d’œufs modifié par plasma d’air humide pour l’élimination des colorants en solution aqueuse.

Abstract

This study focuses on the synthesis of a composite from kaolinite and eggshells by heat treatment and plasma treatment « glidarc » for the removal of dyes in aqueous solution. The main interest of using kaolinite and eggshells in this work is the development of new effective, ecological and economical adsorbents. In this context, adsorbents were prepared by mixing kaolinite and eggshells and the process was optimized based on the evaluation of the removal rate relative to the mass ratio of the constituents and the calcination temperature. Under these conditions, we obtained the material ESC (mass ratio is 3:1) and ESC-800 (calcined at 800 °C). The latter was processed by the sliding arc plasma process to obtain ESC-800/PL. The surface and structural properties of the materials after treatment were characterized by zero charge point measurement (pHPCN), Fourier Transformed Infrared Spectroscopy (TFIR), X-ray diffraction (XRD), thermogravimetric analysis (ATG/DTG), N2 nitrogen adsorption BET analysis and scanning electron microscopy (SEM) combined with X-ray dispersive energy (EDX) microanalysis. The main modification induced the formation of porous platelet agglomerates resulting from the transformations of kaolinite into metakaolinite and CaCO3 into CaO, favoring a structural reorganization accompanied by a more or less pronounced densification. These are physico-chemical transformations that lead to both a modification of the different phases of the crystalline structure (dehydroxylation, amorphization, decarbonation, oxidation, etc.), and the microstructure and texture of the product resulting from the modification or creation of pores. For example, the specific surface area and total pore volume increased from 14 m2.g-1 to 89 m2.g-1 and 0.049 cm3.g-1 to 0.061 cm3.g-1 respectively. At the same time, we recorded a significant increase in removal efficiency from 40 % and 45 % to 80 % and 88 % respectively for the pollutants Fast Green and Orange G. Adsorption tests of OG and FG dyes established equilibrium times of 45 and 30 minutes respectively. At the end of each equilibrium time, the adsorption capacities of OG of 31, 22 and 16 mg.g-1 and FG of 22, 12 and 7 mg.g-1 were obtained with ESC-800-PL, ESC-800 and ESC materials respectively. The adsorption kinetics and isothermal data obtained were better described by a pseudo-first-order kinetic model and Liu's isotherm. This work showed that the ESC-800-PL material has the best adsorbent power vis-à-vis these two dyes studied.