Caracterização e aplicação de nanotubos de carbono de acesso restrito na extração de ferro em soluções aquosas e produção de apoproteínas a partir da catalase

Abstract

Carbon nanotubes (CNT), oxidized carbon nanotubes (oxCNT) and restricted access carbon nanotubes coated with bovine serum albumin (RACNT-BSA) were synthesized and characterized by Transmission electron microscopy (TEM), scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS), Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and zeta potential (ZP). Structural defects were observed by TEM for the oxidized materials. The highest thermal stability was observed for oxCNT and the Raman spectra and zeta potential curves also confirmed the presence of functional groups after acid oxidation. These functional groups are important for the metal adsorption on materials´ surface. The materials were used for the adsorption of iron from aqueous and protein solution and Flame Atomic Absorption Spectrometry (FAAS) was used to detect it. The materials´ adsorption capacities of iron were 44.73 ± 0.29, 43.29 ± 0.11 and 31.55 ± 0.29 mg. g -1 , respectively for CNT, oxCNT and RACNT-BSA. Avrami's fractional model was the one that best fitted the kinetic data for all materials, suggesting that the interaction mechanism is based on chemisorption and physisorption. Regarding the adsorption mechanism by fitting the Weber-Morris model, external and intraparticle diffusion mechanisms were predominant for CNT and oxCNT, and for RACNT-BSA there was preferential adsorption in its external part followed by equilibrium condition. The desorption tests using CNT showed that the maximum desorption of iron ions was obtained using a sodium acetate solution (1.5 mol L -1 ). Reuse tests revealed that the materials can be applied up to 5 successive adsorption/desorption cycles, without loss of efficiency. Thus, CNT and oxCNT can be excellent alternatives for extracting iron from aqueous solutions, while RACNT-BSA has been shown to be efficient in the extraction of iron from protein media, being promising for the preparation of biological samples and in the apoprotein production.