Batch kinetics and thermodynamics of chromium ions removal from waste solutions using synthetic adsorbents

Batch kinetics and thermodynamics of chromium ions removal from waste solutions using synthetic adsorbents

Mg(OH) 2 was identified as a component in the magnesia cement being adsorbent for Cr(VI). Modified magnesia cement was prepared by the addition of ferric chloride and humic acid. The equilibrium adsorption of Cr(VI) on magnesia cement adsorbents (MF5-1) and (MF5-2) was investigated as a function of...

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Bibliographic Details
Published in:Journal of hazardous materials Vol. 142; no. 1; pp. 118 - 129
Main Authors: Gasser, M.S., Morad, GH.A., Aly, H.F.
Format: Journal Article
Language:English
Published: Amsterdam Elsevier B.V 02-04-2007
Elsevier
Subjects:
Adsorption
Applied sciences
Chemical engineering
Chromium
Chromium - isolation & purification
Diffusion
Exact sciences and technology
General purification processes
Isotherm
Kinetics
Mechanism
Pollution
Thermodynamics
Wastewater
Wastewaters
Water Pollutants, Chemical - isolation & purification
Water treatment and pollution
Thermodynamics
Adsorption
Chromium
Isotherm
Kinetics
Wastewater
Mechanism
Organic matter
Coolant
Adsorption isotherm
Activation
Liquid waste
Entropy
Iron III Chlorides
Waste water
Batchwise
Nuclear power plant
First order
Cement
Aqueous solution
Thermodynamic properties
Diffusion
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Summary:Mg(OH) 2 was identified as a component in the magnesia cement being adsorbent for Cr(VI). Modified magnesia cement was prepared by the addition of ferric chloride and humic acid. The equilibrium adsorption of Cr(VI) on magnesia cement adsorbents (MF5-1) and (MF5-2) was investigated as a function of contact time, adsorbent weight, solute concentration and temperature. Tests of different isotherms have shown that the adsorption data fit the Langmiur and Freundlich isotherms at 25 ± 1 °C. The nature of the diffusion process responsible for adsorption of Cr(VI) on (MF5-1) and (MF5-2) adsorbents was discussed. The kinetics and mechanism of diffusion of Cr(VI) into (MF5-1) and (MF5-2) adsorbents from aqueous solution have been studied as a function of Cr(VI) concentrations and reaction temperatures. The adsorption of Cr(VI) on the MF5-1 and MF5-2 adsorbents follows first-order reversible kinetics. The forward and backward constants, k 1 and k 2 have been calculated at different temperatures between 10 and 50 °C. The heat of activation of the adsorption, Δ H * and Δ S * were calculated for Cr(VI) at 25 °C. The values of Δ H * were found 18.1 and 10.7 kJ mol −1 for MF5-1 and MF5-2, respectively, while entropy change, Δ S *, were found −106.8 and −118.6 J mol −1 K −1 for MF5-1 and MF5-2, respectively. The study showed that pore diffusion is the rate-determining step in the adsorption of Cr(VI) ions for MF5-1 and MF5-2. MF5-2 was found more efficient for Cr(VI) adsorption than MF5-1. Also Cr(VI) can be adsorbed on MF5-2, whereas Cr(III) cannot. So, the competitive adsorption of multi-metals onto the MF5-2 adsorbent was studied. The studies showed that this adsorbent can be used as an efficient adsorbent material for the removal of Cr(VI) from water and nuclear power plant coolant water.
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ISSN:0304-3894
1873-3336
DOI:10.1016/j.jhazmat.2006.07.065