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.

This study synthesized a highly efficient KOH-treated sunflower stem activated carbon (KOH-SSAC) using a two-step pyrolysis process and chemical activation using KOH. The resulting material exhibited exceptional properties, such as a high specific surface area (452 m²/g) and excellent adsorption capacities for phenol (333.03 mg/g) and bisphenol A (BPA) (365.81 mg/g). The adsorption process was spontaneous and exothermic, benefiting from the synergistic effects of hydrogen bonding, electrostatic attraction, and stacking interactions. Comparative analysis also showed that KOH-SSAC performed approximately twice as well as sunflower stem biochar (SSB), indicating its potential for water treatment and pollutant removal applications. The study suggests the exploration of optimization strategies to further enhance the efficiency of KOH-SSAC in large-scale scenarios. These findings contribute to the development of improved materials for efficient water treatment and pollution control.