Biossorção do corante amarelo reativo B2R em resíduo orgânico da extração do óleo de semente de chia (salvia hispanica): um estudo cinético, de equilíbrio e termodinâmico

Abstract

The textile industries are responsible for the consumption of approximately 60% of the existing synthetic dyes in the fabric dyeing stage, of which 10 to 15% are discarded in the wastewater. The inefficiency or lack of removal treatment of these dyes confers a serious environmental impact to the environment, reducing the penetration of light in water bodies and making photosynthesis impossible. Dyes most often have toxic and carcinogenic properties. Conventional methods may not be as efficient in the removal of dyes from textile effluents. An efficient alternative in dye removal is the biosorption process, which has characteristics of capturing the desired component through a biosorbent. The residual meal of chia seeds is an industrial organic residue from the oil-extracting process of chia seeds and there are neither applications for this, nor an environmentally correct destination. The potential of the residual meal of chia seeds as biosorbent in the removal of the Reactive Yellow B2R dye in a batch system was evaluated in this project. Initially preliminary tests were performed with the goal of finding the best operating conditions, which were pH 2, temperature of 30oC, agitation speed of 150 rpm and the particle diameter applied in the experiments was the mixture, since it presented excellent 87% of removal against 90% of the smallest particle, eliminating a unit operation process. The kinetic, equilibrium and thermodynamic studies were performed in triplicate and in batch system. The kinetic study was performed at the temperatures of 30, 40 and 50oC, and concluded an equilibrium time of 60 hours, with removal of approximately 92%. However, the beginning of the study was marked by the increase of the reaction speed related to the increase of the temperature. The kinetic model of pseudosecond order was fitted to the obtained data. In the equilibrium study the Toth isotherm as adjusted to the data with a R2 of 0.9927 and heterogeneity parameter of 1,27, characterizing a slightly heterogeneous bisorbent surface. The maximum sorption capacity determined by Toth was 70,95 mg g-1. The thermodynamic parameters characterized the biosorption process as endothermic with increased disorder of the molecules after the biosorption, and it occurs spontaneously and favorably at the temperatures under study. Finally, the activation energy presented a value of 33,82 kJ mol-1 indicating that the adsorption process is physical in nature.