Polymerization of graphene oxide with polystyrene: Non-linear isotherms and kinetics studies of anionic dyes

This study describes the preparation of graphene oxide modified with polystyrene (GO-PS) and its application to Reactive Blue 19 (RB 19), Direct Red 81 (DR 81) and Acid Blue 92 (AB 92) adsorption from aqueous media. The adsorbents were characterized by Brunauer-Emmett-Teller (BET) technique, Fourier transform-infrared resonance (FTIR) spectroscopy, Energy-dispersive X-ray (EDX) spectroscopy and scanning electron microscopy (SEM) analysis. The average pore diameter of graphene oxide (GO) increased from 4.853 nm to 7.051 nm after polymerization. Adsorption capacities of GO-PS for dyes removal were evaluated through batch studies. For Reactive Blue 19, Direct Red 81 and Acid Blue 92 dyes (with an initial dye concentration of 20 mg/L), the adsorption capacities of final adsorbent were found to be 13.13, 19.84 and 15.44 mg/g, respectively. The adsorption equilibrium, isotherm and kinetic non-linear models were tested for the adsorption process and the experimental data were best fitted by the Freundlich isotherm with the high correlation coefficient (R-2) of 0.999. The maximum adsorption capacities of dyes were achieved 43.280, 40.663 and 39.067 mg/g for Direct Red 81, Acid Blue 92 and Reactive Blue 19, respectively, by using the Langmuir isotherm model. Moreover, the adsorption kinetics of the dyes on GO-PS was well-described by Elovich (for Reactive Blue 19) and intraparticle diffusion models (for Direct Red 81 and Acid Blue 92). The results of this research revealed that GO-PS is a promising adsorbent for removal of anionic dyes in aqueous solution.