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International Journal of Environment Science and Technology
Center for Environment and Energy Research and Studies (CEERS)
ISSN: 1735-1472
EISSN: 1735-2630
Vol. 11, No. 4, 2014, pp. 987-996
Bioline Code: st14097
Full paper language: English
Document type: Research Article
Document available free of charge

International Journal of Environment Science and Technology, Vol. 11, No. 4, 2014, pp. 987-996

 en Raw and calcination-modified coal waste as adsorbents to remove cadmium from simulated mining wastewater
Zhang, M. & Wang, H.

Abstract

The adsorption of cadmium from simulated mining wastewater by coal waste (CW) and calcinationmodified coal waste (MCW) was investigated. Effects of pH, initial concentration, particle size of adsorbent, adsorbent dosage and temperature were studied in batch experiments. The adsorption efficiency for cadmium increased with increasing pH, and the optimum pH for cadmium adsorption onto MCW and CW was 6.0 and 6.5, respectively. Kinetic experiments showed that the adsorption equilibrium was reached within 120 min and followed pseudo-second-order model well. The adsorption isotherm data fit Langmuir and Freundlich models, and the adsorption capacity of cadmium on the two adsorbents increased with increasing temperature from 298 to 318 K. MCW had a higher adsorption capacity of cadmium than CW, because calcination treatment can make CW to have more loose structure and higher specific surface area. Thermodynamic parameters, the Gibbs free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°), were calculated and the results showed that the adsorption of cadmium on CW and MCW was spontaneous and endothermic. Fourier transform infrared studies indicated silanol and aluminol groups were responsible for cadmium binding. The desorption results indicated that the two adsorbents could be used repeatedly at least three times without significant decrease in the adsorption capacity for cadmium. The results suggested that modified CW could have high potential as low-cost adsorbent for cadmium removal.

Keywords
Adsorption; Desorption; Heavy metal; Thermodynamic parameters

 
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