Efficient removal of toxic azo dyes from contaminated water by adsorption on the GO surface.

The purpose of this study is to examine the possibility of GO to be used as an adsorbent for five novel potentially hazardous azo-dyes for their removal from aqueous solution. Adsorption characteristics of GO for azo-dyes removal were investigated by means of experimental and computational DFT as well as Monte Carlo approaches. Experimental studies include the effect of adsorbent dose, contact time, and initial concentration, while computational investigation involves DFT and Monte Carlo (MC) simulations. Through DFT studies geometric, electronic, and thermodynamic parameters were explored and possible mechanism of interactions and adsorption energies by predicted through MC by searching lowest possible adsorption complexes. Experimental data were evaluated by Langmuir models in order to describe the equilibrium isotherms. Equilibrium data fitted well to the Langmuir model. Thermodynamic parameters i.e., free energy change, enthalpy change, and entropy change revealed that the removal of azo-dyes by adsorption on the surface of GO molecular sieves was spontaneous. Nature of the process was found to be physiosorption involving non-covalent interaction. The study unveiled that GO can be used as an efficient adsorbent material for the adsorption of azo-dyes from aqueous solution.