Adsorption kinetics and intraparticulate diffusivities for bioremediation of Co (II), Fe (II) and Cu (II) ions from waste water using modified and unmodified maize cob

Abstract

Heavy metals constitute pollution problems to the environment and they are toxic to both man and aquatic organisms. The passive removal of toxic heavy metals such as cobalt (II) (Co(II)), iron (II) (Fe(II)) and copper (II) (Cu(II)) by inexpensive biomaterials, termed biosorption, requires that the substrate displays high metal uptake and selectivity, as well as suitable mechanical properties for applied remediation scenarios. The kinetics and intraparticulate diffusivities for the adsorption of these metal ions onto modified and unmodified maize cob was investigated. The amount of the metal ions adsorbed increased as time increased. The trend of the sorption capacity was found to be Co(II) > Fe(II) > Cu(II) for unmodified and Co(II) > Cu(II) > Fe for EDTA modified maize cob. The mechanism of adsorption of the metal ions followed particle diffusion model. The pseudo-first order and pseudo- second order kinetic equations were used to model the adsorption kinetics, with the second order giving a better fit, as seen from the correlation coefficient (R2) which ranged from 0.2329 to 0.9958 for pseudo first order and 0.9994 to 1.008 for pseudo-second order model. The applicability of the Elovich equation to the sorption kinetics was also investigated. This work therefore shows that modified and unmodified maize cob could be used to remove Co(II) Fe(II) and Cu(II) ions from waste water and also established their mechanism of sorption. Key words: Bioremediation, adsorption kinetics, heavy metal, maize cob.