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Removal of chromium (VI) from aqueous solution using walnut hull
Xue Song Wang1, Zhi Zhong Li, Sheng Rong Tao
1Department of Chemical Engineering, Huaihai Institute of Technology, Lianyungang, Jiangsu, China. snowpine1969@yahoo.com.cn
Journal of Environmental Management
|March 18, 2008
Summary
Walnut hull effectively removes chromium (VI) from water, achieving 97.3% removal at pH 1.0. This low-cost adsorbent shows promise for practical water treatment applications.
Area of Science:
- Environmental Science
- Water Treatment Technologies
- Adsorption Processes
Background:
- Chromium (VI) is a toxic heavy metal pollutant found in industrial wastewater.
- Effective and economical methods for chromium (VI) removal are crucial for environmental protection.
- Natural, low-cost adsorbents offer a sustainable alternative to conventional treatment methods.
Purpose of the Study:
- To investigate the efficacy of walnut hull as a low-cost adsorbent for chromium (VI) removal from aqueous solutions.
- To optimize adsorption conditions including pH, contact time, and concentrations.
- To evaluate the adsorption mechanism and thermodynamic parameters.
Main Methods:
- Batch adsorption experiments were conducted to study chromium (VI) removal.
- Adsorption was investigated as a function of pH, contact time, adsorbent/adsorbate concentration, temperature, and supporting electrolyte.
- Adsorption kinetics and isotherms were analyzed using various models (e.g., Langmuir, Freundlich, Elovich).
Main Results:
- Maximum chromium (VI) removal of 97.3% was achieved at pH 1.0.
- Adsorption kinetics followed first-order and Elovich models, suggesting a chemically controlled process (Ea = 102.78 kJ/mol).
- Langmuir and Freundlich isotherms effectively described the biosorption, with optimal chromium (VI) concentration at 240-480 mg/L and adsorbent concentration at 1.0-5.0 g/L.
Conclusions:
- Walnut hull is a highly effective and low-cost biosorbent for chromium (VI) removal.
- Adsorption is influenced by pH, temperature, and electrolyte concentration, with optimal performance at acidic pH and higher temperatures.
- The study demonstrates the significant potential of walnut hull for practical application in treating chromium (VI)-contaminated water.
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