Alkali pretreated sugarcane bagasse, rice husk and corn husk wastes as lignocellulosic biosorbents for dyes

Abstract Lignocellulosic residues of sugarcane bagasse (SCB), corn husk (CHW) and rice husk (RHW) were evaluated as renewable and low cost bioadsorbents of the methylene blue dye. Residues were treated with a 0.10 mol L−1 NaOH solution to remove part of the polymeric component of the fibers and to intensify the dye adsorption. They were characterized by chemical composition, SEM, ATR-FTIR, BET, XRD and pHzpc. The adsorbents were evaluated using the 23 full Box-Behnken design with the variables pH, dye concentration and adsorbent dosage, obtaining descriptive mathematical models for adsorption percentage and also the response surfaces. Cellulose, hemicellulose and lignin were the main constituents of the materials analyzed, totalizing 81 to 91 g 100 g −1, whose lignocellulosic groups were verified by ATR-FTIR. The wastes presented high percentage of adsorption: 95.7 ± 1.9 % for SCB, 98.5 ± 1.2 % for CHW and 95.4 ± 0.8 % for RHW at the central point of the experimental design. Therefore, alkali treatment provided an interesting alternative to produce efficient bioadsorbents from agroindustrial wastes.