Biosorción de cromo VI en soluciones acuosas con cascarilla de cacao modificada con ácido cítrico

Abstract

Materials were obtained from cocoa husk, using three particle sizes (0.125 to 0.150 mm, 0.155 to 0.25 mm and 0.25 to 0.45 mm) and three concentrations of citric acid (0.3 M, 0.25 mm). , 6 M and 0.9 M); the chemical modification was carried out at a temperature of 60 ° C for 12 h, after which the sample was dried at 100 ° C for 5 h, and washed with water. The biosorbent material was characterized by: acidity and total basicity, pH of the zero charge point, proximal analysis and infrared analysis. The performance of the materials obtained in the removal of Cr VI in synthetic aqueous solutions was evaluated through the determination of its kinetic behavior and of the adsorption isotherms at a temperature of 25 ° C, pH of 2.0 and an initial concentration of Cr VI of 50 ppm; the data obtained were adjusted to the pseudo first and pseudo second order models, while the adsorption isotherm data were adjusted to the Langmuir and Freundlich models; the kinetic results presented a better adjustment to the pseudo second order model, while the data of the adsorption isotherms presented a better fit to the Langmuir model. The highest adsorption capacity was 115.28 mg / g, when the material with a particle size between 0.25 and 0.45 mm was used, without citric acid treatment; Among the samples treated with citric acid, the highest adsorption capacity was 105.15 mg / g, with the smaller material (0.125 to 0.150 mm), treated with 0.9 M citric acid. Analysis of variance of the results obtained showed that there was no significant effect of the variables evaluated on the adsorption capacity of Cr VI of the samples obtained.