Adsorción de arsénico y antimonio en soluciones acuosas mediante aplicación de biomasa lignocelulósica de cáscara de cacao

Abstract

The objective of this research was to determine the capacity of adsorption using the cocoa shell, as an adsorbent material, for two metalloids such as Antimony Sb (III) and Arsenic As (III). The cultivation of cocoa is one of the main economic activities of the province of El Oro. The cocoa husk is a residue that is obtained after the harvest of cocoa which can be exploited by the ease of obtaining it and by the large quantities of waste that causes, since the farmer uses the cocoa beans from this fruit, the rest is discarded in the plantation soil causing the contamination to increase more; In our country there is a lot of pollution in water sources, so we have started to look for new sources to minimize pollution levels, taking advantage of this way these cocoa residues for the adsorption of metals in water, since this waste is due to Its components such as cellulose, hemicellulose and lignocellulose favor the adsorption of heavy metals. The characterization of the material consisted in the determination of the potential of zero charge, morphological and compositional analysis by means of scanning electron microscopy (SEM) coupled to X-ray diffraction, and infrared spectroscopy (FTIR). Within the parameters that were used for the evaluation in the process of adsorption of the metalloids, we performed: pH study, equilibrium studies and adsorption kinetics. The determination of the zero charge potential of the cocoa shell was obtained, obtaining as a result that the equilibrium point is of pH 6.90; later To this analysis a pH study was carried out, where the optimum pH was established, which produces a higher percentage of adsorption for the metalloids Sb (III) and As (III), thus, tests were carried out at different pHs for each metal, with solutions of concentration of 50 ppm of Sb (III) and As (III), and at pHs of 1, 2, 3, 4, 5, 6, 8, 10, they were made in triplicate, and it was determined that the highest percentage of adsorption of Sb (III) is carried out at pH 8 and for As (III) it was at pH 5. Once the optimum pH of both metalloids was obtained, we proceeded to perform analysis for the construction of isothermal curves and adsorption kinetics. The capacity of adsorption in all the analyzes was represented through isotherms and was better adjusted to the mathematical model of Langmuir with a maximum capacity of adsorption (qmax) of 168.88 mg / g and a correlation coefficient R2 = 0.97503 for Sb (III), while for As (III) a qmax of 65.16 mg / g and a correlation coefficient R2 = 0.90082 was obtained; and for the kinetic adjustment gave favorable results with the Pseudo first order model qmax: 53.084 and correlation coefficient R2: 0.93 for Sb (III), and for As (III) a qmax of 43.2277 with a correlation coefficient R2: 0.84 This experimental research work revealed that the cocoa husk is an efficient material for the adsorption process of Sb (III) and As (III), thus minimizing the environmental pollution caused by them.