Graphene oxide functionalized with L-asparagine applied to crystal violet dye removal from water and wastewater

The efficiency of graphene oxide functionalized with L-asparagine (GO@L-Asn) as adsorbent for crystal violet (CV) dye removal from water and wastewater was investigated. The surface and textural properties of this new nanomaterial were characterized by pH at point of zero charge, Fourier-transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and Brunauer-Emmet-Teller technique. The main experimental variables involved in dye adsorption process were evaluated and optimized. Adsorption equilibrium was reached after 120 min, using 25 mL of 50 mg L^-1 CV, and 30 mg of GO@L-Asn at pH 8 and 328 K. The Freundlich isotherm model was the most appropriate to correlate the experimental data, showing a maximum adsorption capacity of 102.5 mg g^-1 (R² = 0.992). The results of the kinetic study were fitted with the pseudo-first order model (R² = 0.997). Thermodynamic calculations indicated that the CV removal was an endothermic, spontaneous, and favorable process. Characterization and modeling results showed that an adsorption mechanism involving physisorption was associated with CV removal. This novel adsorbent was applied to remove CV from samples of natural water and textile effluents, obtaining pollutant removal percentages up to 92.0%, which indicated the high efficiency of GO@L-Asn for the treatment of complex matrices.