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Abstract
Peat, being a partially decomposed organic material, consists of many organic compounds, such as humic acids and fulvic acids, which contain phenolic, carboxylic acid and amino functionalities, contributing to unique surface characteristics. Firing of peat leads to the loss of organic matter, thus changing the point of zero charge and controlling the extent of adsorption. The change in the initial pH of Cr(VI) solutions does not significantly change the pH of the suspension of Muthurajawela peat (MP) materials and Cr(VI) solutions, maintaining a constant extent of removal. The optimum conditions for the removal of Cr(VI) are 2.0 h shaking time, 1.0 h settling time, 200°C firing temperature and an ambient pH of 3.8–4.2, leading to a high extent of removal of 120 mg kg−1. The sorption of Cr(VI) on MP fulfills the requirements of the Freundlich adsorption model with a high regression coefficient. Further, the sorption of Cr(VI) on peat is a pseudo-second-order process at moderate solution temperatures.
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Acknowledgement
The authors wish to thank the National Science Foundation of Sri Lanka for providing research grant (RG/2012/BS/02).