Journal
FOOD CHEMISTRY
Volume 132, Issue 2, Pages 693-700Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.foodchem.2011.10.099
Keywords
Adsorption isotherms; Hexavalent chromium; Walnut shell; Citric acid modification
Funding
- Selcuk University Scientific Research Foundation [05101014/2005]
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Walnut shell (WNS) (Juglans regia) has been utilised as an adsorbent for the removal of Cr(VI) ions from aqueous solutions after treatment with citric acid. The modification reaction variables, such as citric acid level (5-10 g), reaction time (0-24 h), and temperature (110-130 degrees C) were studied in batch experiments. The rate of adsorption was studied under a variety of conditions, including initial Cr(VI) concentration (0.1-1.0 mM), amount of adsorbent (0.02-0.20 g), pH (2-9), temperature and contact time (10-240 min). Adsorption of Cr(VI) is in all cases pH-dependent showing a maximum at equilibrium pH values between 2.0 and 3.0 for citric acid modified walnut shell (CA-WNS). The applicability of the Langmuir, Freundlich and D-R adsorption isotherms has been tested for the equilibrium. Maximum adsorption capacities of CA-WNS and untreated WNS under experimental conditions were 0.596 and 0.154 mmol/g for Cr(VI) ions, respectively. (C) 2011 Elsevier Ltd. All rights reserved.
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