Use of a Luffa cylindrica/polypyrrole composite for removing dyes from aqueous media

We report the preparation of a Luffa cylindrica/polypyrrole (LC/PPy) composite and its use for the removal of tartrazine dye (E102) from aqueous media. By use of Fourier transform infrared (FTIR) and energy-dispersive X-ray (EDX) spectroscopies, X-ray diffraction (XRD) and scanning electron microscopy (SEM), we were able to confirm that the PPy chains thoroughly coat the LC matrix, with the composite presenting both amorphous and crystalline phases such as pristine LC. We examined the effects of varying parameters, such as the times allotted for the polymerization and the dye–adsorbent interaction, the E102 initial concentration and the temperature and pH of the solution, on the removal capacity (q_e) of the composite. The largest adsorption rate was exhibited by the composite resulting from a 30 min polymerization. At 298 K, the highest value of q_e (374.2 mg g⁻¹) occurred at pH 2.0, after 360 min of interaction. The adsorption process occurs spontaneously and is favored by an increase in temperature, with q_e = 672.4 mg g⁻¹ at 313 K. We determined that the composite could be used in at least five consecutive adsorption–desorption cycles without noticeable losses of properties. Preliminary experiments indicate that good results were also obtained for the removal of the dyes Remazol Black B, methylene blue and toluidine blue. Overall, these results suggest that the LC/PPy composite is a promising material for use in protocols of removal of dyes from aqueous media. © 2023 Society of Industrial Chemistry.