Adsorción de iones Cr(VI) sobre lechos adsorbentes calcinados con superficie de carga variable químicamente modificada

Abstract

This work describes the Cr(VI) ion adsorption on calcined substrates prepared with refractory oxidic lithologic materials from Lagunillas, Mérida state, Venezuela. The study was performed on raw material as well as on three calcined substrates; two of these were chemically treated in acidic and alkaline medium to generate positive and negative charges respectively. Thermal treatment favors amphoteric oxides formation with ZNCP around pH 6.5. Adsorption isotherms fit to BET model with C values between 0 and 1 and it is 10 times greater for the chemically treated substrates. The performance of the adsorption reaction is 2.5 times greater on the substrate treated in acidic media. During the adsorption reaction, the pH variation suggests a proton exchange in the first monolayer which are replaced by dichromate ions, especially on the acidic treated substrate. Desorption study indicates that there is 50% less desorption from the positively charged surface, which suggest a greater affinity between dichromate ions and the latest.