O Uso da biomassa residual do cacau como uma proposta de oficina temática para o ensino de equilíbrio químico

Abstract

This work presents a proposal for the use of residual cocoa biomass as a precursor material for the production of activated carbon for use in adsorption processes of pollutants in water. And aiming to make a didactic transposition for the teaching of chemistry, a proposal for a thematic workshop entitled Residual Biomass as a strategy for teaching chemistry is also developed in this work, in which the content of chemical equilibrium will be addressed from this workshop. Brazil is on the list of the world's largest cocoa producers, and this means that there is a significant generation of residue from this fruit, since 80% of the fruit corresponds to the bark that is destined for the garbage. In view of the importance of developing viable alternatives for the treatment of residues obtained from cocoa, studies were carried out to characterize the cocoa husk biomass through immediate analysis, EDX, TGA/DTG, FTIR and DRX. The results obtained for moisture content (11.2%), ash (6.77%), volatiles (79.68%), fixed carbon (2.36%) and minerals (by EDX) showed values consistent with data reported in the literature of the area. The activated charcoal (CA COCOA) obtained under study was prepared by the pyrolysis process at a temperature of 800 ºC for 2 hours. The activated carbon produced in this study was obtained with a yield of 25.95%. The characterizations for the CA COCOA of PZC, TGA/DTG, FTIR and DRX were also carried out. In addition, studies of adsorption isotherms were carried out in order to understand the adsorption behaviour of malachite green (VM) dye on CA COCOA through chemical equilibrium, chemical kinetics and thermodynamics studies. For the kinetic study, the data fit better for the pseudo-second order reaction. The thermodynamic study indicated that the adsorption process is endothermic and CA COCOA-VM interactions occurred spontaneously. Finally, to evaluate the thematic workshop proposal, the data collection method was used in the form of a semistructured questionnaire to obtain an opinion from the teachers about the workshop proposal. The results obtained through the characterization and adsorption studies of CA COCOA show that the cocoa husk residue has adequate characteristics to be used in the development of adsorbent materials for the removal of potentially toxic substances, in addition it was also evidenced through the validation of the workshop proposed under study that it has great potential for teaching chemistry.