Adsorption of residual amine collector HAY from aqueous solution by refined carbon from coal fly ash and activated carbon

Refined carbon (RC) derived from coal fly ash (CFA) as well as powdered activated carbon (PAC) was investigated as adsorbent to remove residual amine collector HAY from aqueous solution. The RC and PAC were characterized by scanning electron microscopy (SEM), surface area measurement, Zeta potential measurement and Fourier transform infrared (FTIR) spectroscopy. The effect factors and mechanisms of HAY adsorption onto RC and PAC were studied in detail. The results show that the experimental kinetic data agree well with the pseudo second-order equation, and the Langmuir isotherm model is found to be more appropriate to explicate the experimental equilibrium isotherm results than the Freundlich model. The adsorption capacities of PAC and RC increase with pH. It is found that alkaline condition is conducive to the adsorption of HAY onto PAC and RC and the adsorption efficiency of RC is close to PAC at pH near 11. Zeta potential variation of adsorbents suggests that HAY generates electrostatic adsorption onto RC and PAC. FTIR analysis shows that the adsorption is dominantly of a physical process. The Box-Behnken design optimization conditions of process are RC 1 g/L, pH 11, temperature 302 K and initial HAY concentration 100 mg/L. Under these conditions, the measured adsorption ratio and adsorption capacity are 87.91% and 87.91 mg/g, respectively. Thus, the RC is considered to be a potential adsorbent for the removal of residual amine from aqueous solution.