Effect of oxidative treatment on composition and properties of sorbents prepared from sugarcane residues

Efficient sorbents for the removal of cationic dye were prepared from sugarcane bagasse (stalk) and straw (leaves) by oxidative pre-treatment with hydrogen peroxide (H2O2) in acetic acid. The effects of variables, such as concentration of H2O2, temperature and time on the properties of the fiber sorbents obtained were studied according to a 2(3) full-factorial design. For comparison, an oxidative treatment of sugarcane biomass with glacial acetic acid was also used. The yields of the materials obtained and their chemical composition were characterized and compared. Fourier transform infrared spectroscopy, field-emission scanning electron microscopy and benzene vapor adsorption were used to investigate the structural properties and morphology of the initial materials and sorbents. The sorption of methylene blue dye was used to assess the efficiency of dye removal by the sorbents. The pre-treatment conditions significantly affected the sorbent yield, their chemical composition (contents of cellulose, lignin and ash) as well as their sorption properties. The cellulosic sorbent (C-sorbent) from sugarcane bagasse obtained by pre-treatment with H2O2 in acetic acid and the lignocellulosic sorbent (LC-sorbent) from sugarcane straw obtained by pre-treatment with glacial acetic acid, had the highest sorption capacity for the methylene blue dye. For both types of sorbents, the sorption capacity increased with chemical pretreatment as a result of an increase in pore volume.