▎ 摘　　要

This work deals with the preparation of a new graphene oxide derivative replaced with long-chain quaternary ammonium salt through grafting with arenediazonium salts in order to enhance its amphiphilic character and broad the adsorption spectra. Raman and Fourier-transform infrared spectroscopies and x-ray diffraction analyses confirmed the incorporation of the ammonium salt into the graphene oxide. After characterization, the new nanomaterial was used in the synthesis of magnetic composite with chitosan. The synthesized magnetic composite was characterized by several techniques, including magnetization curve, and then applied to basic brown 4 dye removal. The optimization of the dye adsorption process was performed by varying parameters such as pH, time, temperature, material loading and dye concentration, among others. Under optimized conditions, the magnetic composite reached high dye adsorption, confirmed by removal capacity of 650 mg/g, and 95% of dye removal. Nanocomposite reuse studies were also performed and in three consecutive adsorption cycles, showing 64% of dye uptake efficiency. The composite ability to remove the basic brown 4 dye is greater than for other materials reported in the literature, as carbon nanotubes and active carbon, among others. After dye adsorption, the magnetic composite was removed from the aqueous medium by magnet field application, showing to be a potential filter agent with easy removal after use.