Research Article
Adsorption Behavior of Cu(II) Ions on Thermally-Treated Peat of Muthurajawela, Sri Lanka
N. Priyantha1,2, L.B.L. Lim3, S.Wickramasooriya1,2and C.H. Ing3
1Department of Chemistry, University of Peradeniya, Peradeniya, Sri Lanka.
2Postgraduate Institute of Science, University of Peradeniya, Peradeniya, Sri Lanka.
3Department of Chemistry, Universiti Brunei Darussalam, Brunei Darussalam.
Submitted: August 3, 2018; Accepted: May 30, 2019
Abstract
Muthurajawela peat (MP), being organic in nature, undergoes many physical and chemical transformations when subjected to heat treatment, as evident by Fourier transform infrared spectroscopic and thermogravimetric measurements. Thus, treatment temperature of peat is a crucial parameter to be optimized for metal sorption studies, which is determined to be 200 °C for Cu(II) removal. At lower temperatures, pores are not sufficiently exposed, while higher temperatures lead to the combustion of organic matter restricting complexation with Cu(II) ions. Investigation of the effect of shaking time and settling time on the extent of Cu(II) removal by MP treated at 200 °C leads to optimum values of 2.5 h and 1.0 h, respectively. Adsorption equilibrium studies of Cu(II) solutions on MP at different solution temperatures verify the suitability of the Freundlich adsorption isotherm, while kinetics data lead to the validity of the pseudo second order model. Adsorption studies of Cu(II) on humic acid, extracted from MP (M-HA) and pre-fired at 200 °C, performed under ambient pH provide evidence that humic acid plays a major role in the Cu(II) removal process, and that the Freundlich isotherm is satisfied better than the Langmuir model. The positive standard enthalpy change (∆H0ads) for adsorption of Cu(II) on both MP and M-HA suggests the endothermic nature of the removal process.
Keywords
Peat; humic acid; copper; adsorption; thermodynamics; kinetics.
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