Estudo de adsorção pelo carvão ativado produzido a partir das sementes de mamão (Carica papaya Linnaeus)

Abstract

The activated carbon is the most used adsorbent due to its excellent adsorptive capacity, however, its limitation in the use of raw material is one of the main causes of its high cost of production. Agroindustrial wastes are an alternative as precursors in the manufacture of activated carbons because they are accessible sources of carbon, allowing the obtainment of an adsorbent with characteristics similar to those produced commercially. In this context, the objective of this work was to produce a granular type chemically activated carbon from papaya seeds (Carica papaya Linnaeus), using sodium hydroxide as an activator and using the software Statistica 12.0, were evaluated the influence of pyrolysis temperature and impregnation time on the production yield and adsorption rate, as well as, adjusted the data obtained to Langmuir and Freundlich models and their parameters were obtained. The impregnation time and pyrolysis temperature followed a factorial design with two factors and two levels (2²), in which the studied impregnation time varied from 1 to 3 h and the pyrolysis temperatures studied were from 400 ºC to 600 ºC. The statistical study of the data obtained showed that the pyrolysis temperature was the operational variable that significantly influenced the yield of production of activated carbon with a maximum value of 49,92% for pyrolysis temperature of 400 ºC and impregnation time equal to 3 h, as well, the impregnation time was the significant factor for the adsorption rate with a positive effect on this, whose maximum adsorption rate was (94,37 ± 0.05)% for activated carbon obtained at 600 ºC with impregnation time of 3 h. The fit of the equilibrium concentration values to the linearized Langmuir and Freundlich models showed that the adsorption phenomenon was best explained by the Langmuir model with an R² of 0,99, indicating homogeneity on the activated carbon surface and monolayer formation during the adsorption process. The maximum amount of adsorption of methylene blue dye by activated carbon (qmax) was 18,3554 mg/g with Freundlich adsorption constant of 2,8026, separation factor RL equal to 0,3443 and heterogeneity constant 1/n of 0,5367, indicating good adsorption capacity, as well as demonstrating that the adsorption process was favorable according to the shape of the isotherm obtained from the experimental data.