Immobilization of calixarene bearing carboxylic acid and amide groups on aminopropyl silica gel and its sorption properties for Cr(VI)
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An aminopropyl silica gel-immobilized calixarene (CAPS) containing both amide and acid moieties was prepared from p-tert-butylcalixarene hexacarboxylate derivative and aminopropyl silica gel in the presence of N,N′-diisopropyl carbodiimide coupling reagent. CAPS was used to evaluate the sorption properties of Cr(VI) as a sorbent material. In sorption studies, it was observed that CAPS was highly effective at pH 1.5 for Cr(VI). The effect of parameters such as pH, sorbent dosage, contact time, initial Cr(VI) concentration and temperature on Cr(VI) sorption; the sorption isotherms were also studied. Maximum sorption capacity was obtained as 3.1 mg g−1 at pH 1.5 and 25 °C for 1 h and 10.4 mg L−1 initial Cr(VI) concentration. Thermodynamic parameters such as change in free energy, enthalpy, and entropy were also determined. In the isotherm studies, Langmuir and Freundlich isotherm models were applied and it was found that the experimental data confirmed to Freundlich isotherm model, and the batch sorption capacity of CAPS was calculated as 37.66 mg g−1.
KeywordsCalixarene Aminopropyl silica gel Immobilization Sorption Chromium(VI)
We thank the Scientific Research Projects Foundation of Selcuk University (SUBAP) for financial support of this work.
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