Removal of Organic Dyes in Environmental Water onto Magnetic-Sulfonic Graphene Nanocomposite

A magnetic-sulfonic graphene nanocomposite (G-SO 3 H/Fe 3 O 4 ) was synthesized and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. It was used for removal of three cationic dyes: safranine T (ST), neutral red (NR), victoria blue (VB), and three anionic dyes: methyl orange, brilliant yellow, and alizarin red, from environmental water. The experimental conditions were optimized, including pH, amount of adsorbent, adsorption kinetics, adsorption isotherms, ionic strength, etc. The results show that G-SO 3 H/Fe 3 O 4 can adsorb cationic dyes more efficiently and selectively than anionic dyes at pH 6.0. In the first 10 min of adsorption time, more than 93% of the cationic dyes were removed by the sorbent. Adsorption kinetics follow the pseudo-second-order kinetic model well. The adsorption isotherm coincided with Langmuir and Freundlich adsorption models. The maximum adsorption capacities of G-SO 3 H/Fe 3 O 4 for ST, NR, and VB dyes were 199.3, 216.8, and 200.6 mg g −1 . The adsorbed cationic dyes were eluted by using different pH values of ethanol as the solvent. The established method was simple, sensitive, and rapid, and was suitable for the adsorption of cationic dyes in environmental water.