Thermodynamics of the adsorption of nickel ions from aqueous phase using graphene oxide and glycine functionalized graphene oxide

Adsorption capacity of Ni^{2 +} on graphene oxide (GO) and glycine functionalized graphene oxide (GO-G) surfaces was well investigated and elucidated. Amino group was used to functionalizing agent for the surface modification of GO to GO-G. The effect of numerous influential parameters such as contact time, temperature and initial concentration of Ni^{2 +} in the aqueous solution was well illustrated and optimized using batch adsorption study. The optimized values of adsorbent dose, initial concentration of Ni^{2 +}, contact time, and pH were found to be 20 mg, 15 mg/L, 50 min, and 6 respectively, ongoing through the impact of temperature it was seen that, when the temperature was increased from 283 to 308 K, the removal of Ni^{2 +} by GO surface decreased but the removal of Ni^{2 +} by functionalized GO-G surface decreased until 298 K and after that it was increased. Adsorption isotherm study for the adsorption process was carried out using four types of the Langmuir and Freundlich isotherm models. Results clearly depict that adsorption of Ni^{2 +} ions on to the GO adsorbent surface was well fitted and found to be in good agreement with the type (II) Langmuir isotherm model as the obtained regression constant value (R²) is found to be 0.999 while the adsorption of Ni^{2 +} on GO-G surface was found to be in good agreement with the Freundlich isotherm model because the regression constant value (R²) is found to be 0.999.