Synthesis and characterization of graphene oxide for adsorptive removal of crystal violet from aqueous solution

Graphene oxide was synthesized from graphite via a modified Hummers method and evaluated for the adsorptive removal of crystal violet from aqueous solutions. Adsorbent characterization was performed using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). FTIR spectra confirmed the successful oxidation of graphite, with the appearance of hydroxyl, carbonyl, and epoxy functional groups. SEM micrographs revealed transformation from the compact layered morphology of graphite to an exfoliated sheet-like structure, while XRD patterns indicated an increase in interlayer spacing due to oxygen functionalization. Batch adsorption experiments were conducted to investigate the effects of initial dye concentration, adsorbent dosage, solution pH, agitation speed, and contact time on crystal violet removal. Plackett–Burman design identified solution pH, dye concentration, and adsorbent dosage as the most significant variables. Optimization using Box-Behnken design achieved maximum removal efficiency of 99.98% at pH = 4.5, dye concentration = 5.0 mg/L, and adsorbent dosage = 0.6 g/L. Kinetic data fitted the pseudo-second-order model ( = 0.998), suggesting chemisorption as the dominant mechanism, while equilibrium data were best described by the Langmuir isotherm ( = 0.955), indicating monolayer adsorption on a homogeneous surface. The enhanced removal efficiency of graphene oxide is attributed to its high surface area and abundant oxygen-containing groups, which enable strong electrostatic attraction toward cationic crystal violet molecules. This study demonstrates that graphene oxide is an efficient adsorbent for crystal violet removal, with potential applicability in industrial wastewater treatment systems.