Nacer Bezzi
University of Bejaia, Algeria
Title: Valorisation of the natural phosphate waste by adsorption of amino-acids
Biography
Biography: Nacer Bezzi
Abstract
Adsorption tests were carried out in static mode on natural phosphate waste samples in a raw state and after processing. Various techniques of analyses were used (1) To characterize the material adsorbing on the granulo-chemical and thermo-mineralogical levels, (2) To evaluate the performances of the process of adsorption used in relation to the existing mineralogical species in phosphatic and gangue elements, (3) To evaluate incubation condition in ions PO43-, carboxylate grouping and steric obstruction effect on lateral chains of adsorbates. This effect is significantly affected by the composition of the incubation medium. Thus, the fractions that are low in phosphate ions appeared definitely more effective. The physico-chemical characterization of the waste phosphate samples by the previous techniques (DRX, MEB, IR) revealed appreciable differences on granulometric, mineralogical, chemical and structural levels. These differences had a remarkable influence on the performances of the adsorption process of the phosphate amino-acid couple. Adsorption tests revealed that the fixing of the amino-acids on this kind of substrate is appreciably affected by the composition of the incubation medium. Examination of the influence of the composition on this substrate in PO43- ions showed that they obstruct the adsorption processes. For a given adsorbent, the quantity adsorbed at saturation of alanine is higher than that of aspartic acid. This is partly related to the steric obstruction of these molecules. The quantity of amino-acid adsorbed at equilibrium is more important for adsorbents that are low in phosphate ions. Thus, under the experimental conditions used and whatever the type of adsorbate, the adsorbent which adsorbs more than (1.45 mmol/g) is the raw phosphate. The phosphate treated by calcination at 900° C during 20 mn involved a considerable drop of the adsorption quantity. This is probably related to specific surface, mineralogical and chemical composition of the used adsorbents as well as the effect of the steric obstruction of side chains of both amino-acids and particularly aspartic acid. The results obtained also revealed a good correlation between experimental points and values predicted by the Temkin model compared to the other models. This clearly confirms the influence of interaction effects of adsorbates loaded on the adsorption processes.