Adsorption Kinetics of Lead and Zinc Ions by Coffee Residues
Chung-Hsin Wu1, Chao-Yin Kuo2, Shu-Shian Guan3
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1Department of Chemical and Materials Engineering, National Kaohsiung University of Applied Sciences,
415 Chien Kung Road, Kaohsiung, Taiwan
2Department of Environmental and Safety Engineering, National Yunlin University of Science and Technology,
123 University Road, Sec. 3, Douliou, Yunlin, Taiwan
3Department of Environmental Engineering, Da-Yeh University, Da-Tsuen, Chang-Hua, Taiwan
Submission date: 2014-07-16
Final revision date: 2014-09-18
Acceptance date: 2014-09-23
Publication date: 2015-04-02
Pol. J. Environ. Stud. 2015;24(2):761–767
Untreated coffee residues (UCRs) were used to remove heavy metal ions from aqueous solutions. The effects of solution pH, heavy metal ions, and UCR concentrations on heavy metal ion removal by UCRs were determined. The removal percentage for heavy metal ions increased as pH and UCR doses increased; conversely, it decreased as the concentration of heavy metal ions increased. This study employed the pseudo firstand second-order kinetics models, the intraparticle diffusion model, and the Bangham model to simulate adsorption kinetics of Pb2+ and Zn2+ onto UCRs. Simulation results indicate that adsorption kinetics fit well with the pseudo second-order model. After reaction for 180 min at [adsorbate] = 20 mg/L, [UCRs] = 2 g/L, and pH 5, the adsorption percentage of Pb2+ and Zn2+ was 96% and 44%, respectively; moreover, the adsorption density of Pb2+ and Zn2+ onto UCRs was 9.7 and 4.4 mg/g (4.7×10-2 and 6.8×10-2 mmol/g), respectively. The adsorption of Pb2+ and Zn2+ onto UCRs is controlled mainly by surface diffusion.