Optimization of parameters with experimental design for the adsorption of mercury using polyethylenimine modified-activated carbon

This study reports a facile hydrothermal method to synthesize polyethylenimine-modified activated carbon derived from waste tires (PEI-AC). The obtained material was characterized by Fourier transform infrared spectroscopy (FTIR), Scanning Electron microscopy (SEM) equipped with Energy-Dispersive X-ray spectroscopy (EDX), Thermogravimetric analyzer (TGA), and Brunauer-Emmett-Teller (BET) analyzer. The adsorption efficiency of the new adsorbent for the removal of Hg(II) was evaluated under the effects of its concentration, temperature, adsorption contact time, medium pH and re-usability. The optimum experimental conditions were found under response surface methodology (RSM)using central composite design (CCD). The results of the study show very good adsorption performance and high regeneration efficiency; the adsorption data fitted well into pseudo-second order model. The Langmuir monolayer capacity was determined to be 16.39 mg g^-1. The exothermic enthalpy change (ΔH) of -24.65 kJ mol^-1 and negative Gibbs free energy change (ΔG) assured the viability of the adsorption process. Therefore, the material leverages its cheap source and ease of regeneration in combination with its high and fast uptake capacities to offer a great promise for wastewater remediation.