Preparation, adsorptive properties and chemical regeneration studies of high-porous activated carbon derived from Platanus orientalis leaves for Cr(VI) removal

Activated carbon (AC) was prepared from Platanus orientalis leaves by H3PO4 activation using a microwave heating method and characterized by SEM (scanning electron microscopy), Brunauer-Emmett- Teller (BET) surface area analysis and FTIR (Fourier transform infrared spectroscopy) techniques. AC exhibited a surface area of 1089.67 m(2)/g and a relatively high pore volume of 1.468 cm(3)/g. Utilization of AC for the removal of Cr(VI) from aqueous solution was researched. The adsorption efficiency was highly pH dependent and adsorption capacity of AC for Cr(VI) could reach up to 135.24 mg/g. Adsorption equilibrium could be quickly reached within 2 h. A kinetic study indicated that the adsorption of Cr(VI) conformed to the pseudo-second-order model (R-2 > 0.99). An intraparticle diffusion model was applied to describe the adsorption kinetics, and the results showed that there are other factors that affect the rate. Chemical regeneration for AC saturated with Cr(VI) was performed and HNO3 displayed the best regeneration performance among the four chemical regeneration agents (HNO3, H2SO4, NaOH, NaCl). The regeneration performance increased at first and then decreased with the rise of HNO3 concentration, and regeneration reaction could reach equilibrium within 4 h in the first cycle. The FTIR spectra revealed that HNO3 successfully introduced N-H bonds onto the AC surface in the regeneration process.