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Enhanced phosphate removal from aqueous solution by ferric-modified laterites: Equilibrium, kinetics and thermodynamic studies

Huang, W-Y, Zhu, R-H, He, F., Li, D., Zhu, Y. and Zhang, Y-M (2013) Enhanced phosphate removal from aqueous solution by ferric-modified laterites: Equilibrium, kinetics and thermodynamic studies. Chemical Engineering Journal, 228 . pp. 679-687.

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The phosphate removal performances of a series of ferric-modified laterites (ML) were tested and compared with raw laterite (RL) in this study. After the modification with 0.5M FeCl3 solution, the resulting adsorbent ML-C exhibited 90.12% of phosphate removal, which was 37.47% higher than that of RL under the same experimental condition. This may be attributed to the significant increase of BET surface area and total pore volume for ML-C, arising from the formation of akaganeite. The effects of contact time, initial phosphate concentration, temperature, pH, and co-existing ions on the adsorption capacity of ML-C were investigated in detail. The equilibrium data of ML-C were fitted better by the Freundlich model than the Langmuir model, suggesting the heterogeneity of the adsorbent surface. The maximum adsorption capacity was estimated to be 31.53mg P/g at 25°C, which decreased with increasing temperatures. The negative change in free energy (δG°) and in enthalpy (δH°) indicated that the adsorption was a spontaneous and exothermic process. The phosphate adsorption kinetics was better described by the pseudo-second-order model, which indicated the adsorption process was chemisorption. Phosphate removal capacities decreased with increasing pH. The presence of 0.001M and 0.01M completive ions, e.g. Cl-, NO3-, SO42-and HCO3-, had neglectable effects on the phosphate adsorption. In the reusability study, the adsorbent showed no significant loss in their adsorption performance after four adsorption-desorption cycles, indicating that ML-C was able to be utilized as a potential cost-effective phosphate adsorbent for practical applications.

Item Type: Journal Article
Murdoch Affiliation(s): School of Engineering and Information Technology
Publisher: Elsevier
Copyright: © 2013 Elsevier B.V.
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