Determinación de los parámetros de adsorción de cromo (VI) sobre residuos de mandarina (Citrus reticulata)

Abstract

In the present investigation, the optimum parameters for the adsorption of chromium (VI) on mandarin (Citrus reticulata) residues were determined. Two adsorbent materials were obtained, the first one only with a physical treatment of drying, grinding and sieving, while the second material was also subjected to a chemical treatment of pectin cross-linking. The materials obtained were characterised by FTIR spectrophotometric analysis, where the presence of functional groups characteristic of pectin, cellulose, hemicellulose and lignin, responsible for the adsorbent character of the biomass, was identified. Adsorption tests were carried out with both materials, varying the particle size, pH and dosage, one at a time, in such a way that the optimum values could be identified. For both materials, the particle size had no major effect on diameters from 2mm and the optimum pH was set at a range between 2.5 and 3. The optimum dosage for 50mL of sample with 50ppm chromium (VI) was 3 and 2 grams for the physically and physico-chemically treated material, respectively. The contact time for both materials was determined in 10 and 20 minutes, respectively. Finally, the performance was evaluated in an adsorption process on a real sample from a tannery, applying the parameters established as optimal; it was possible to adsorb around 83% of chromium (VI) in 50mL of a sample with a concentration of 100.35ppm, a very satisfactory result considering that biomass was used without any treatment or chemical activation. For a more efficient implementation, a continuous fixed bed design is recommended, as well as the treatment of the material with other chemical agents for its activation.