Adsorption of Lead(II), Manganese(II), and Copper(II) onto biochar in landfill leachate: implication of non-linear regression analysis

Abstract

The feasibility of using wood-derived biochar (BC) to remove Pb, Mn, and Cu from landfill leachate was investigated and modeled in this study. The effect of contact time, biochar dosage and particle size on adsorption of the heavy metals onto BC was examined. BC was used in two form i.e. pulverized (PWB) and crushed (CWB) to evaluate the effect of BC particle size on adsorption characteristics. Biochar was produced under the pyrolytic temperature of 740 °C. The kinetics of Pb, Mn, and Cu adsorption onto PWB and CWB were assessed using the pseudo second-order and Elovich models, where both applied models could well describe the adsorption kinetics. Removal rates of the heavy metals were raised by 1.2, 1.4, and 1.6 times, respectively, for Pb, Mn, and Cu, when PWB content of the leachate increased from 0.5 to 5 g L -1 . Equilibrium adsorption capacity of the heavy metals onto BC in leachate system was evaluated using the Langmuir, non-linearized Freundlich, linearized Freundlich, and Temkin isotherms and found to have the following order for PWB: Non-linearized Freundlich>Temkin>Langmuir>Linearized Freundlich. The Langmuir and linearized Freundlich models could not adequately represent adsorption of the heavy metals onto biochar, especially for CWB. The highest removal of 87.96% was obtained for Pb, while the greatest adsorption intensity was found to be 1.58 mg g -1 for Mn. Using the non-linearized Freundlich isotherm significantly reduced adsorption prediction error. The adsorption affinity of PWB for Pb, Mn, and Cu was greater than CWB in all treatments. Wood-derived biochar is suggested to be used for the removal of heavy metals from landfill leachate as an economical adsorbent.