Adsorção de corante cristal violeta em cinza de lavador de gases proveniente de atividade agroindustrial

Abstract

In this work, the sludge derived from gas washer and generated during the production of fertilizers was employed as low cost adsorbent for the removal of aqueous solution of crystal violet (CV) dye. The material was used in four distinct forms: washed with deionized water (LAD), treated with acetic acid (LAA), treated with sulfuric acid (LSA) and treated with sodium hydroxide (LHS). The materials were characterized by means of X-ray fluorescence (XRF), CHN-S elemental analysis, vibrational Fourier transform-infrared spectroscopy (FTIR), zeta potential and specific surface area (BET). The adsorption process was optimized using surface response methodology developed by the application of a complete factorial planning with 11 experiments, considering the minimum, intermediate and maximum points of three independent variables: pH, initial dye concentration (mg L -1 ) and adsorbent mass (g), with the adsorption capacity (Q e) as response variable. The optimized adsorption conditions were of pH 3.5, initial dye concentration of 170 mg L -1 and adsorbent mass of 0.07 g. The kinetic adsorption study, conducted using the optimized conditions, established that the equilibrium time was of 122, 35, 91 and 45 minutes for LAD, LAA, LAS and LHS, respectively. The kinetic data for LAD were better adjusted for the pseudo-first order model, while for LAA, LAS and LHS, the data were adjusted to the pseudo-second order model. The maximum adsorption capacities for LAD, LAA, LAS and LHS were of 107.3, 77.3, 95.6 and 94.6 mg L -1 , respectively. The adjusted isotherm data showed that the Sips model was the most satisfactory for all adsorbents. The results showed that there was no significant difference in CV adsorption by the treated adsorbents in the in natura form, the most efficient and economic form of use for gas washer residue in removing crystal violet dye.