Síntese e caracterização do carvão ativado obtido da frutífera de maracujá

Abstract

The northeast of Brazil is one of the largest producers of passion fruit and produces a large amount of waste as a by-product of its activities, which has no defined destination. The accumulation of this waste without specific application causes an environmental problem, such as the fruit waste not used by pulp industries. We therefore proposed using this waste to produce biochar through the process of thermal degradation of organic matter, known as pyrolysis. After chemically activating the biochar, this material has greater chemical and thermal stability. With this in mind, priority was given to studying the properties of activated carbons from the residual biomass of passion fruit trees obtained via incipient impregnation using H3PO4 and ZnCl2. The coals were prepared from treated residual biomass (CAM/H3PO4 and CAM/ZnCl2) and the biochar precursor obtained from biomass pyrolysis (CAMB/H3PO4 and CAMB/ZnCl2). The physicochemical properties of the raw biomass, biochar and activated carbons were investigated using thermogravimetric analysis (TG/DTG), proximate analysis, infrared spectroscopy (FTIR), X-ray diffraction (XRD), point of zero charge (PCZ) and surface area (BET). FTIR data from the activated carbons showed absorptions related to C=C stretching related to aromatic structures, with the acid-activated carbons showing absorptions of phosphorus and phosphocarbon compounds (hydrogen bonded to P=O; aromatic P-O-C, and P=OOH groups), as well as confirmation of a predominantly amorphous or disordered structure identified by XRD. Thermal analysis (TG/DTG) showed that the biochar and charcoal samples activated with H3PO4 and ZnCl2 had good thermal stability. The results of the immediate analysis showed a higher content of volatile materials (72%) in the passion fruit biomass compared to the passion fruit biochar (PM) and the coals activated with ZnCl2 and H3PO4 (< 10%). The pyrolyzed materials (CAMB/H3PO4 and CAMB/ZnCl2) showed a higher percentage of fixed carbon and ash, which is to be expected given that they are materials that have undergone the carbonization process. For the coals activated with ZnCl2 and H3PO4, the zero charge point results were 3.02 and 6.42, respectively. Finally, the characterization of the surface area of each sample revealed that CAMB/H3PO4, CAM/H3PO4 and CAMB/ZnCl2 did not develop considerable porosity, with the exception of CAM/ZnCl2, which showed a surface area of 713m2.