Evaluation of Biochar derived from partial pyrolysis of Chara Algae for adsorption of lead and copper from aqueous solutions A

This study aimed to evaluate the efficiency of biochar (BC) produced from Chara algae via semi-anaerobic pyrolysis as an adsorbent for removing lead (Pb²⁺) and copper (Cu²⁺) ions from aqueous solutions in a batch system. The preparatory process involved washing the algal biomass with tap water and deionized water, followed by a two-stage drying process: solar drying (48 h) and then thermal drying (75°C, 24 h). Dried sample was then ground into fine particles (250–400 μm) and subjected to a semi-anaerobic heat treatment at temperatures between 400 and 600°C for 50 min to adjust the physicochemical properties of the biochar. The adsorption performance was studied under a range of operating conditions, including a range of pH (2–6), contact time (10–150 min), initial heavy metal ion concentrations (20–100 mg/L), temperatures ranging from 25 to 80°C, and various adsorbent concentrations (0.1–3 g/L). The adsorbent was characterized using advanced analytical techniques. Fourier transform infrared spectroscopy (FTIR) was used to identify the functional groups active in adsorption, scanning electron microscopy (SEM) to analyze the surface structure, and energy-dispersive X-ray spectroscopy (EDS) to determine the elemental composition and confirm metal adsorption. Under best conditions (pH 6, dosage 1.0 g/L), the maximum adsorption capacities recorded were 322 mg/g for Pb²⁺ and 196 mg/g for Cu²⁺. The dynamic adsorption studies further confirmed the removing heavy metals from aqueous media, indicating its promise for scalable water treatment. applications.