Avaliação do mecanismo de adsorção do metronidazol em carvão ativado da casca do coco babaçu

Abstract

This work has evaluated the adsorption capability of three coal produced in the Universidade Estadual do Oeste do Paraná (tilapia bone residual coal, soybean bark coal and chestnut from Pará) and other kind of coal commercially obtained (babaçu coconut pealing coal) to remove the metronidazole from aqueous solution. The coal which better absorbed the metranidazole was the babaçu coconut peal one (CCCB) with temperature from 40ºC, 150 rpm of stirring and with no pH adjustment. Thus, the kinetic tests were performed by using the SOTAX dissolution apparatus, with 1000 mL of metronidazole solution, varying the concentration (200, 400, 650 and 850 mg/ L) and the temperature (30, 40, 45ºC), 1 g of the coal and 150 rpm of stirring. The equilibrium time observed was around 20 hours and in the first 4 hours a bigger amount of metranidazole was adsorbed, this inicial amount corresponds to the metranidazole adsorption in the outer layer of the CCCB. The results obtained from the adsorption kinetics were described by the intraparticule diffusion in which were verified the appearing of four well defined regions corresponding to the adsorption in the outer layer, in the macropores, in the CCCB mesopores and the equilibrium, respectively. In the equilibrium studies, were presented two adsorption mechanisms: monolayer and multilayer with increasing concentration of the adsorbate, corresponding to the hybrid model of Langmuir + BET. The removing process of metranidazole by using CCCB became economically viable due to the low cost in the obtention or production of the adsorbent, the easily extracetion of the babaçu coconut biomass and the excellent capability of maximum adsorptive to the metranidazole.