Evaluation of adsorption properties and structural characterization of the husk and mesocarp of Caryocar brasiliense for application as an adsorbent

The pequi (Caryocar brasiliense) stands out for having significant economic value through its fruits in cooking. However, despite the numerous applications of the pequi, few studies are available on the socioeconomic importance of using the peel, fruit, and almond. Therefore, finding applications for its residues is essential; to this end, developing research that uses bioadsorbents– adsorbent materials of natural origin– becomes relevant for the scientific community. In this perspective, this study aimed to evaluate the adsorption properties and characterize the peel and mesocarp of the pequi as a potential application for the treatment of effluents from the textile industry. The fruit was separated into peel and fruit, placed in an oven, and ground in a mill after drying. After the grinding process, the material obtained had its particles classified into different particle sizes. The particle size of the peel chosen for the study was 45 mesh. After selecting the particle size, part of the material was calcined in a muffle furnace at 400 °C for 4 h. Subsequently, the bioadsorbents were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), surface area by the BET method, and scanning electron microscopy (SEM). The XRD analysis showed that the bioadsorbents presented predominantly amorphous structures. In the textural properties, the bioadsorbents were presented as a porous material, and it was also possible to observe that in the thermally calcined mesocarp material, this offered a larger surface area. Meanwhile, the morphological analysis showed that a more significant and deeper number of cracks and pores appeared in the thermally calcined bioadsorbents compared to the in natura bioadsorbents. Thermally calcined bioadsorbents achieved excellent adsorption capacity, which provided 90% dye removal efficiency in just 5 min, for both the bark bioadsorbent and the mesocarp bioadsorbent, proving to be a good system for dye removal in aqueous media. Therefore, replacing biomass as an adsorbent is feasible, since, compared to other synthetic materials, they have a reduced cost and are abundant.

Graphical abstract