Cr(VI) sorption behavior from aqueous solutions onto polymeric microcapsules containing a long-chain quaternary ammonium salt: Kinetics and thermodynamics analysis

详细信息    查看全文

• 作者：Giancarlo Barassi ; Andrea Valdé ; s ; Claudio Araneda ; Carlos Basualto ; Jaime Sapag ; Cristiá ; n Tapia ; Fern ; o Valenzuela
• 关键词：Chromium (VI) ; Sorption ; Microcapsules ; Thermodynamic parameters
• 刊名：Journal of Hazardous Materials
• 出版年：2009
• 出版时间：15 December 2009
• 年：2009
• 卷：172
• 期：1
• 页码：262-268
• 全文大小：507 K

文摘

This work studies the adsorption of Cr(VI) ions from an aqueous acid solution on hydrophobic polymeric microcapsules containing a long-chain quaternary ammonium salt-type extractant immobilized in their pore structure. The microcapsules were synthesized by adding the extractant Aliquat 336 during the in situ radical copolymerization of the monomers styrene (ST) and ethylene glycol dimethacrylate (EGDMA). The microcapsules, which had a spherical shape with a rough surface, behaved as efficient adsorbents for Cr(VI) at the tested temperatures. The results of kinetics experiments carried out at different temperatures showed that the adsorption process fits well to a pseudo-second-order with an activation energy of 82.7 kJ mol⁻¹, confirming that the sorption process is controlled by a chemisorption mechanism. Langmuir's isotherms were found to represent well the experimentally observed sorption data. Thermodynamics parameters, namely, changes in standard free energy (ΔG⁰), enthalpy (ΔH⁰), and entropy (ΔS⁰), are also calculated. The results indicate that the chemisorption process is spontaneous and exothermic. The entropy change value measured in this study shows that metal adsorbed on microcapsules leads to a less chaotic system than a liquid–liquid extraction system.