Avaliação da eficiência adsortiva do carvão ativado obtido da vagem de algaroba (Prosopis juliflora) como adsorvente na remoção de gasolina presente em água.

Abstract

Currently, one of main environmental concerns is contamination of soil and water by harmful organic substances, such as gasoline, diesel and other chemicals, which represent a significant threat to the environment. In an attempt to solve this problem, adsorption appears as an effective purification and separation solution, with several applications, especially in treatment of effluents. In this work, performance of physically activated carbon (PAC) and physically and chemically activated carbon (PCAC) derived from mesquite pods (Prosopis juliflora) in adsorption of gasoline present in water was evaluated. For this purpose, adsorption kinetics and equilibrium experiments were carried out, followed by use of Langmuir and Freundlich isotherm models, to identify which of these best fitted the experimental data. Study carried out by Paiva (2023) using activated carbon derived from mesquite pods proved to be efficient up to 60 minutes of contact between the biomass and water/gasoline mixture. Therefore, this work aimed to analyze if increasing contact time would provide more satisfactory and complete results. The same methodology was used as proposed by Lima et al. (2014), in which biomass was initially prepared with natural drying, followed by comminution of material in particulate form. For production of activated carbon, Morais (2014) methodology was used for carbonization, followed by washing, filtration and drying, obtaining physically activated carbon (CAF). In the second stage, chemical activation was followed using potassium hydroxide (KOH) solution for 30 minutes, under stirring at 140 rpm, in order to obtain physically and chemically activated carbon (CAFQ). It was followed by study of adsorption kinetics, in which times 5 to 120 minutes (5-minute intervals) were evaluated. Equilibrium study, whose concentrations varied from 5% to 50% (5% variation rate), was also carried out. As a result, it was observed that adsorption kinetics of CAF obtained a maximum adsorption of 3.542 g.g-1 at times 25, 60, 80, 105 and 110 minutes, while with CAFQ, maximum adsorption was 4.583 g.g-1 at 110 minutes. Equilibrium studies obtained maximum capacity of 7.3 g.g-1 and 8.13 g.g-1, for CAF and CAFQ biomass, respectively. Isotherms obtained confirmed that, in both systems, adsorption occurred in multilayers, since the best fit occurred with Freundlich model. However, study with longer contact time, although important, proved to be unnecessary, as more relevant results were not obtained when compared to previous studies.