Adsorção de corantes em materiais híbridos obtidos de biomassa pirolisada com nanopartículas magnéticas

Abstract

The adsorption of residues in aqueous medium is an effective process for treating effluents from the textile industry. Several materials have been developed for this purpose, and their adsorptive capacity has been thoroughly studied. In this work, a new adsorbent material was synthesized by a hydrothermal route. This hybrid material (named HB) is formed by biomass residue (sugarcane straw) and magnetite nanoparticles (NPs), an iron oxide. The magnetite cubic phase in HB was identified by X-ray diffraction. The Fe-O vibrational band, characteristic of iron oxide, was observed by infrared spectroscopy. HB presented a globular morphology, with a wide range of size (between 500 nm and 2 m). The performance of HB as an adsorbent was evaluated through the adsorption of the dyes Congo Red (VC) and Indigo Carmine (IC). The concentrations studied varied between 6.97 and 69.67 mg.L-1 for VC and between 4.66 and 46.64 mg.L-1 for IC. The adsorption kinetics curves showed that the saturation time of HB for both dyes was around 120 h. Most of the adsorption (around 71 % for the VC and 28 % for the IC) occurred in the first 24 h of contact between the adsorbent and the dyes. This indicates the feasibility of using HB on an industrial scale, mainly in the treatment of water contaminated by VC residues. The adsorption kinetics for both systems followed the Pseudo Second Order model, with 99% correlation for VC, and 82% for IC. For the adsorption isotherms, the Langmuir, Freundlich and Temkin models satisfactorily described the HB/VC system (above 95 % correlation) and the Freundlich and Temkin models described HB/IC (above 92 % correlation). The results presented show that HB has potential for adsorption of dyes in aqueous medium.