Avaliação da remoção de corante em efluentes têxteis utilizando algas arribadas (Sargassum sp.) como adsorvente

Abstract

The treatment using the adsorption technology for the removal of dye in textile effluents, in addition to presenting high removal efficiency, is easy to operate. In the present study, the drying of the seaweed Sargassum sp., and its potential as an adsorbent, in natura and chemically activated, in the removal of the dye Methylene Blue in a synthetic textile effluent was evaluated. The drying process was carried out in a greenhouse with forced air circulation, at temperatures of 60 and 80 °C, until the material had a constant mass. The model that obtained the best fit to the experimental data was that of Midili for both temperatures. The characterization of the adsorbent in natura from the zero loading point obtained the result of 7.97 and for the activated material 8.10. Factorial design 2^4 was applied to the adsorption process with the independent variables adsorbent mass, dye concentration, contact time and chemical activation, and the responses to reduction in dye concentration (%R) and adsorbed quantity (qt) were evaluated. The experiment that obtained the best result in relation to the response variable qt showed a value of 231.90 mg.g^-1 for fresh seaweed and 240.30 mg.g^-1 for activated seaweed. For the %R response variable, the best result was 93.31% for fresh seaweed and 96.85% for activated seaweed. The kinetic tests were performed with the conditions proposed in the experiment that presented the best result in relation to the variable qt, with samples collected every 5 min up to 140 min. For fresh seaweed, the pseudo-second order model obtained the best fit to the experimental kinetics data, and for activated algae the pseudo-first order model obtained the best fit to the experimental kinetics data. The isotherms were constructed varying the concentration from 50 to 300 mg.L^-1 in the period of 120 min. For the data obtained, the Sips isotherm obtained a higher value of R^2 and Test F with values of 0.99 and 253.6453, respectively. For the activated material, the Langmuir isotherm obtained a higher value of R^2 and Test F with values of 0.98 and 40.32, respectively. The adsorbent produced from the seaweed Sargassum sp. obtained satisfactory results in the study of kinetics and adsorption balance, showing efficiency in reducing the methylene blue dye in textile effluent.