Adsorption of copper (II) by peanut hulls in a fixed-bed, continuous flow column

WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
Tyler Stephen Cook (Creator)
Western Carolina University (WCU )
Web Site:
Carmen Huffman

Abstract: Heavy metal pollution is an important concern due to its adverse health and environmental effects. Biosorption is a way to remove heavy metals from aqueous systems with the use of biomaterials. There are many different types of biosorbents, such as algae, fungus, bacteria and lignocellulosic materials (wood, saw dust, peat, wheat bran, nut shells, etc.). Several studies have used peanut shells (hulls) as a heavy metal adsorption material. For instance, peanut hulls are an effective biomass for the removal of copper (II) from aqueous systems. However, these studies utilized equilibrium (batch) methods to quantify metal adsorption. These results are not comparable to an industrial setting, which utilizes a non-equilibrium flow system.The biosorption of copper(II) on unmodified and modified, high density, ground peanut hulls was investigated using equilibrium studies, kinetics studies, and dynamic adsorption studies. Adsorption models were applied to determine the adsorption capacity at equilibrium. A pseudo-second order rate law was applied to the kinetics data to determine the rate constant of adsorption. Dynamic sorption models were applied to the continuous flow studies to fit the experimental breakthrough curves.It was determined that the alkaline peroxide modified, high density hulls had the highest adsorption capacity, the fastest rate of adsorption, and latest breakthrough point. The alkaline modified hulls' adsorption capacity and breakthrough point are decreased from the alkaline peroxide modified hulls but perform better than the unmodified hulls. However, an improvement in the rate of adsorption was not seen in comparison to the unmodified hulls. The unmodified hulls had the lowest adsorption capacity and earliest breakthrough point. The best fitting model for the equilibrium data for all types of hulls was the Redlich-Peterson model. However, the Langmuir model was the most useful as it yielded results with physically meaningful parameters as well as the best estimation of the adsorption capacity. The four parameter Clark model was the best fitting dynamic adsorption model for each type of hulls, followed by the three parameter Clark, and finally the Thomas model. Although the four parameter Clark model resulted in the best fit, the model's parameters are empirical and are not physically meaningful. The Thomas model was the poorest fitting model tested.Although the four parameter Clark model successfully fit the breakthrough data for each type of hull, the empirical nature of the model is not useful for comparing to the equilibrium and kinetics data. However, the more physically meaningful Thomas model does not successfully relate the equilibrium and kinetics parameters to the dynamic flow behavior of the copper(II) /peanut hull adsorption system. There is a need for additional models to be tested and/or developed for these types of systems, as the models tested in this project were developed for other types of systems and applied to the biosorption of heavy metals with poor fit and predictive power.

Additional Information

Language: English
Date: 2017

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