Application of graphene oxide modified with the phenopyridine and 2-mercaptobenzothiazole for the adsorption of Cr (VI) from wastewater: Optimization, kinetic, thermodynamic and equilibrium studies

Abstract In this study response surface methodology (RSM) was discussed as an efficient method for optimization of chromium adsorption onto magnetic graphene oxide(GO-Fe 3 O 4 ) nanocomposites functionalized with two chelating ligands of the phenopyridine (GFP) and 2-mercaptobenzothiazole (GFM). The obtained GFP and GFM nanocomposites characterized using TEM, SEM, FTIR, EDAX, AFM, DLS and TGA. The optimization of adsorption of Cr (VI) onto GFM and GFP was done with the aim of high adsorption performance, minimizing the adsorbent dose and increase of the initial Cr (VI) concentration. Results indicated reduced full second-order (for GFP) and full second-order (for GFM) models were well-fitted with the experimental data. The optimum operating points were achieved (pH, 6.55; adsorbent dosage, 0.098 g L −1 ; contact time, 178.4 min and Cr (VI) concentration, 1 mg L −1 ) and (pH, 6.79; adsorbent dosage, 2.98 g L −1 ; contact time, 118.6 min and Cr (VI) concentration, 4.41 mg L −1 ) for GFP and GFM, respectively. The both adsorbents indicated best fit with Langmuir model. Also, the kinetic models were followed pseudo second order model and pseudo first order model for GFP and GFM, respectively. The thermodynamic studies indicated the sorption of Cr (VI) onto GFP and GFM was endothermic and spontaneous.