Buffalo weed (Ambrosia trifida L. var. trifida) biochar for cadmium (II) and lead (II) adsorption in single and mixed system

Biochars (BWBC 300, BWBC 500 and BWBC 700) derived from buffalo weed (Ambrosia trifida L. var. trifida) at different pyrolysis temperatures of 300, 500 and 700°C were investigated for the removal of Cd(II) and Pb(II) ions from aqueous solutions. The physicochemical properties of the biochars were studied using FTIR, scanning electron microscopy (SEM), X-ray diffraction, Brunauer, Emmett and Teller surface area, cation exchange capacity and energy dispersive X-ray analysis. The adsorption at solution pH = 5 could be well described by Freundlich model for Cd(II) and Pb(II) in their single and mixed system with R2 ⩾ 0.95. The maximum adsorption capacities of the biochar BWBC 700 from the Langmuir equation were found to be 11.63 and 333.33 mg g−1 for Cd(II) and Pb(II), respectively. Pseudo-second-order kinetic model was fitted well in describing the adsorption kinetics of Cd(II) and Pb(II) onto the biochar BWBC 700. About 0.02 mol L−1 disodium salt of EDTA was able to desorb Cd(II) and Pb(II) from the biochar BWBC 700 with an approximately 63.5% and 96.8% desorption yield, respectively. Ion exchange and surface complexation found to be the main mechanisms involved in the adsorption process. The developed biochar derived from Ambrosia trifida L. var. trifida found to be a low cost adsorbent and could be used for the effective removal of Cd(II) and Pb(II) in waste waters.