Assessment and optimization of total ammonia nitrogen adsorption in aqueous phase by sodium functionalized graphene oxide using response surface methodology

Total ammonia nitrogen (TAN) uptake by sodium functionalized graphene oxide as an efficient adsorbent was evaluated and optimized using response surface methodology (RSM). Batch adsorption tests were carried out based on a central composite design experimental plan at 3 pH levels (6, 7, and 8) and 3 temperature levels (5, 25, and 45 degrees C). The equilibrium condition was reached within 5 min. Quadratic models for percent TAN removal (R%) and solid phase TAN concentration (q(e)) as response were obtained and evaluated by statistical analysis to predict the experimental data. The models were reduced by eliminating insignificant terms. The final reduced models were significant (p < .0001) with R-2 values .96 for R% and .97 for q(e), respectively. The optimum pH and temperature to reach the maximum values for R% (58.23%) and q(e) (27.45 mg/g) were predicted by the RSM. The laboratory experiments were in very good agreement with the predicted optimized values for R% and q(e) by RMS as the error was 1.2 and 0.3%, respectively.