Résumé:
This work is devoted to the synthesis and characterization of new series of low-cost adsorbent materials thoroughly regenerable derived from a low value cellulose and lignocellulosic wastes (olive stone and timber sawdust) and their application for the removal of basic dyes from aqueous solutions. Materials of the first series are prepared by covalent grafting of succinate and maleate moieties at the polyol structure of cellulose and lignocellulosic matrices. Analysis of the sorption characteristics show that the association of these spacers bearing negatively charged sorption sites with the biopolymers in hybrid structures leads to materials with enhanced sorption capacities of cationic dyes. On the other hand, sorption studies revealed that the removal of dyes is so fast that equilibrium is reached as soon as the sorbent is wet and the pH change has nearly no effect on the process. Regenerability of the adsorbent materials is quite effective with brine solution and subsequent reuse of the matrices for three repeated cycles led to just a slight attenuation in their performances. The second part aimed at developing the synthesis of a new low-cost adsorbent derived from low value by-product of timber industry by alkaline treatment of the sawdust with aqueous sodium hydroxide. The presence of new functional groups on the surface of the treated material resulted in a dramatic increase of surface polarity and the density of sorption sites, thereby improving by two- to threefold higher adsorption capacities of the cationic dyes than those of the untreated analog. On the other hand, the exothermic nature of adsorption is demonstrated by a decrease of adsorption capacity with increasing temperature, and the negative value of free energy change indicated the spontaneity of adsorption.
