Kinetics of Cu(II) and fulvic acid adsorption on modified biochar derived from rice husk

The kinetics of Cu(II) and fulvic acid (FA) adsorption onto biochar has been investigated. The modified biochar samples derived from rice husks were characterized by scanning electron microscopy equipped with the energy-dispersive X-ray spectroscope and Fourier transform-infrared spectroscopy. Some characteristic parameters, such as specific surface area and zeta potential, were also determined. The optimum condition of Cu(II) adsorption was temperature of 308 K, 2 g L-1 of adsorbent dosage and 25 mg L-1 of FA concentration. The maximum removal efficiencies of Cu(II) ions and FA were almost 81% and 94%, respectively. The experimental data for adsorption of Cu(II) and FA on modified biochar was fitted by various adsorption kinetic models. The results showed that the pseudo-second-order equation was the best-suited model. Elovich equation was consistent with the experimental data suggested chemical interactions between modified biochar and adsorbates. Also, the intraparticle diffusion model fitted the experimental data well, indicating that the process of Cu(II) and FA adsorption was diffusion-controlled. In addition, complexation reactions between FA and Cu(II) promoted the adsorption of adsorbates on modified biochar. The relatively high desorption efficiency proves the strong regeneration capacity of modified biochar.