Desempenho do biocarvão obtido dos resíduos da noz macadâmia na adsorção de β-naftol e corante reativo preto 5

Abstract

The generation of liquid waste containing dyes and complex organic compounds is a problem in the textile industries. In this work, the use of macadamia nut biomass as a precursor of activated carbons for the treatment of these effluents by the adsorption process was evaluated. Thus, the macadamia nut endocarp was previously pyrolyzed at 600°C and then underwent physical activation with CO2 at 700°C. The following techniques were used in the characterization: X-ray diffractometry (XRD) thermogravimetric analysis (TGA), scanning electron microscopy associated with energy dispersive X-ray spectroscopy (SEM-EDS), specific surface area (BET), pore distribution (BJH) and pHPCZ. From the performance studies, it was found that the pH does not have a relevant influence on the adsorption phenomenon, which was adjusted with the Elovich kinetic model for both adsorbates (Radj β−naftol 2 =0,98949 e Radj RB5 2 =0,93557). The intraparticle diffusion model allowed to conclude that the βnaphthol adsorption kinetics is governed by multiple mechanisms, different from the RB5 adsorption kinetics which is driven by intraparticle diffusion. The experimental data of the adsorption equilibrium of both adsorbates obtained a better fit with the isothermal model of Sips and presented maximum adsorption capacity of qmax βnaftol=15,16mg g-1 and qmax RB5=3,08mg g-1 , at 55°C. The adsorption process of both adsorbates was spontaneous and exothermic, with enthalpy values typical of lower energy electrostatic interactions for β-naphthol, compared to the energetic values of interactions between RB5 and the biochar. According to the observations of this work, we can conclude that the biomass of macadamia nut residues has the potential to be used as a precursor of biochar and that it has suitable characteristics to be applied as an adsorbent material in the removal of organic compounds such as β-naphthol and the RB5.