Abstract
Hexavalent chromium removal from wastewater using sheep wool was investigated at several equilibration periods. The influence of contact time, pH, adsorbent dosage and initial concentration was investigated. Adsorption isotherms for long and short periods were fitted to the Langmuir and Freundlich isotherms. For short contact times, the Langmuir adsorption isotherm was obeyed with no detectable change in the oxidation state but removal percentages did not exceed 90%. Long contact times resulted in more than 99% removal of Cr(VI). A 2-step mechanism for the removal is proposed. Free wool and wool loaded with Cr(VI) were characterized by FTIR and SEM.
Highlights
Chromium can exist in various valence states ranging from Cr(II) to Cr(VI), the most stable forms being Cr(III) and Cr(VI) [1]-[3]
The data reveal no dicsernible effect of particle size on Cr(VI) removal efficiency
The Langmuir adsorption isotherm was obeyed with no detectable change in the oxidation state
Summary
Chromium can exist in various valence states ranging from Cr(II) to Cr(VI), the most stable forms being Cr(III) and Cr(VI) [1]-[3] These two forms exhibit large differences in physicochemical properties as well as chemical and biochemical reactivity [2] [3]. This pervasive use results in the discharge of large quantities of chromium into the environment. These include reduction followed by chemical precipitation [6], ion exchange [7], reduction [8], adsorption [9], electrochemical precipitation [10], solvent extraction [11], membrane separation [12], cementation [13], evaporation, reverse osmosis, foam separation, freeze separation, and biosorption [14]
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