Abstract

GIRADO, Liliana  and  MORENO, Juan Carlos. THE RELATION BETWEEN IMMERSION ENTHALPY AND ADSORPTION PARAMETERS FOR AN ACTIVATED CARBON IN AQUEOUS Pb²⁺SOLUTIONS. Rev.Colomb.Quim. [online]. 2006, vol.35, n.1, pp.41-49. ISSN 0120-2804.

We report the preparation of an activated carbon obtained by impregnation of mineral carbon samples with phosphoric acid solution (50%). The obtained material, exhibits a superficial area of 586 m².g^-1 and a total pore volume of 0,37 cm³g^-1. With respect to the chemical properties, the activated carbon shows an increased number of acidic sites (0,92 meq g^-1) compared to basic sites (0,63 meq g^-1 ) which yields a material with almost neutral characteristics (pHpzc: 7,4). At a pH: 4.0 the amount of Pb²⁺ absorbed and the immersion enthalpy values for the activated carbon reached maxima with values of 15.7 mg^-1 y 27,6 Jg^-1 respectively. It was established that similar behaviour occurs for the two properties, absorption and immersion enthalpy, as a function of pH. In addition, a second order function that relates the adsorption constant and immersion enthalpy, and the adsorption constant and pH of the solution are presented.

Keywords : immersion enthalpy; adsorption of Pb²⁺; Langmuir isotherm; pH.

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