Estudo da sorção de cromo (III) em pastilhas de polietileno de baixa densidade (PEBD) e adsorventes naturais (fibra de coco, quitosana e argila)

Abstract

Among the many existing methods for removing heavy metals off the effluents, the adsorption process stands out for being considered most effective, at lower cost. The phenomenon of adsorption consists in a process of the transfer of one or more constituents of a fluid phase to a surface of a solid phase. The adsorption process depends on physical and chemical characteristics, as: structural properties of the adsorbent (porosity, functional groups), adsorbate (ionic radius and coordination number), interaction between adsorbent and adsorbed. New technologies have emerged with focus returned to the use of biological materials with adsorbing properties for the treatment of effluents, in particular, removal and recovery of heavy metals, showing good performance. The main advantages of using natural adsorbents (biosorbents) in the process of sorption are: low waste generation, easy recovery of metals, the possibility of reuse of the adsorbent and lower operating costs, depending on the adsorbent material used in the process. From the foregoing this research used tablets of composite material, formed of recycled low density polyethylene (LDPErec) as polymer matrix and adsorbent materials (coconut fibber FC, chitosan Qui or clay B) and a comparative study using such tablets as adsorbents, to removal of the chromium (III), in order to determine which tablet has a better adsorption of chromium (III).To this end, there were realized three experimental design, where they were evaluated the influence of the size of coconut fibber particles, the composition of LDPErec/Fc, LDPErec/B, LDPErec/Qui, LDPErec/FC/Qui and LDPErec/B/Qui, the concentration of chromium (III) adsorbate and the exposure time of the tablets in the chromium (III) solution. With the results can conclude that the models used in the experimental design were valid for the evaluation of significant variables of this work, as the best chromium (III) removal conditions. That happened to the composition values of 40/60% to the tablets of LDPErec/FC1, LDPErec/FC3 and LDPErec/B. The particle size range of coconut fibber that proved more favourable was smaller particle size (100-120 mesh) in the composition of 40/60 %. The conductivity has been used to predict a chromium (III) sorption model but it proved not to be good parameter