ETUDE DE LA BISORPTION DE CERTAINS COLORANTS BASIQUES

Abstract

Three biosorbents: the leaves of Eucalyptus globulus, Cynara cardunculus and Prunus cerasefera were tested to remove Methylene Blue, Fuchin, Zn (II) and Ni (II) from aqueous solutions. Three biosorbents were characterized by the determination of accessible surface methylene blue, iodine number, BET specific surface area of nitrogen adsorption at 77 K, morphological analysis by scanning electron microscopy, pHpzc and FTIR analysis. The adsorption capacités of biosorbents were studied as a function of pH, biosorbent dose, stirring speed, ionic strength and contact time. The optimum conditions for extracting the maximum pollutants: methylene blue, Fuchin and both heavy metals (nickel and zinc) were determined for three media studied: Eucalyptus globulus, Cynara cardunculus and Prunus cerasefera. Langmuir model determined from experiments recorded a maximum capacity of adsorption by biosorbent prepared from the leaves of Eucalyptus globulus 250 mg g-1 against 333 mg g-1 and 143 mg g-1 for biosorbents prepared from Cynara cardunculus and Prunus cerasefera respectively. Fuchsin for each gram of biosorbents adsorbed: 121.95, 111 and 135.14 mg succession. The experimental data can be also performed by the Temkin equation and Freudlich. The adsorption was spontaneous and exothermic to Methylene Blue, endothermic for the pollutant Fuchin for both adsorbent EUCA and CARD. Retention of two heavy metals (zinc and nickel) was checked under optimal conditions the equilibrium is reached after 60 to 120 minutes for the Ni (II), Zn (II) respectively to acidic pH. the removal performance of the materials prepared are different, the kinetics is second order for the two metals Ni (II) and Zn (II). The adsorption isotherm for the two metals has been studied over a range of low concentrations, the experimental data are well interpreted by the Langmuir, Freundlich and Temkin model with high correlation coefficient. The thermodynamic study for Ni (II) and Zn (II) showed that the retention process is spontaneous (negative free energy) and Exothermic for the three system studied.