Adsorption capacity of biochar and leonardite for lead removal Pb2+ from water

Vera-Marmanillo V.; Pilares L.A.; Vergara R.Z. · Carbon Trends (2026) · DOI: 10.1016/j.cartre.2026.100682

Resumen

The adsorption capacity of biochar and leonardite for lead removal in water was evaluated under controlled laboratory conditions. The physical and chemical characteristics of both materials were analyzed, including porosity via Scanning Electron Microscopy (SEM), Total Organic Carbon (TOC) via the Walkley-Black method, and elemental chemical analysis via Energy Dispersive Spectroscopy (EDS). Optimal factors (pH, adsorbent dose, agitation speed, and contact time) were determined by applying an experimental design consisting of 4 treatments with double replication for determining the optimal pH and 9 treatments with triple replication for determining the dose, contact time, and agitation speed. The micrographs demonstrated that biochar exhibits a porous structure with a pore diameter size between 20.21μm and 32.30μm. The surface area of biochar at a particle size of 0.250 mm is 28.85 m²/g and the TOC is 35.295 g/kg. Leonardite did not exhibit porosity, which led to its activation with Calcium Chloride (CaCl₂); its total carbon content was 31.1%. EDS analysis revealed a high total carbon content for both biochar and leonardite. The optimal adsorption pH was 5 for both materials. Since each experimental unit contained 50 mL of solution, the applied adsorbent dosages correspond to 2.0 mg mL⁻¹ (100 mg), 1.5 mg mL⁻¹ (75 mg) and 1.0 mg mL⁻¹ (50 mg) for leonardite. Biochar performed better at 50 rpm and 10 min, whereas leonardite was optimal at 100 rpm and 20 min. Statistical analysis revealed that both dose and agitation speed are significant factors for adsorption. Contact time did not present a significant main effect (p > 0.05); however, a significant three-way interaction among dose, agitation speed and contact time was observed for biochar, indicating that the influence of contact time depends on the simultaneous levels of the remaining operational variables. Leonardite removed 99.19% of the lead, proving to be a highly effective option, while biochar achieved 55.83% removal.

Instituciones: Universidad Nacional de San Antonio Abad del Cusco