Hybrid nanomaterial from pyrolyzed biomass and Fe 3 O 4 magnetic nanoparticles for the adsorption of textile dyes

Industrial dyes are harmful compounds often present in wastewater. In this work, a magnetic nanohybrid material (HB) was hydrothermally synthesized from pyrolyzed sugarcane straw (CN) and magnetic iron oxide nanoparticles. The material was characterized by XRD, FTIR, SEM, TGA, and PZC, and tested for the adsorptive removal of congo red (CR) and indigo carmine (IC) dyes from aqueous solutions at pH 7.0 and 10.0, respectively. The kinetics of adsorption was well explained by both the pseudo-second order (PSO) model ( R_adj^2∼ 0.99 for CR, 0.96 for IC) and the Elovich model ( R_adj^2 0.98 for CR, 0.98 for IC). After 24 h, the maximum adsorption capacities of the material were 18.39 mg g −1 for CR and 1.46 mg g −1 for IC. Adsorption isotherms were obtained at 25, 35, and 45 °C, and four different models were tested. The Sips model, which combines Langmuir and Freundlich, was used to fit the data. HB exhibited greater performance removing CR dye (