Pb(II) adsorption by biochar from co-pyrolysis of corn stalks and alkali-fused fly ash

Numerous studies have reported the potential of silica as a biochar (BC) modifier. However, despite its high silica content, fly ash is rarely used for BC modification. Herein, modified BCs were produced by co-pyrolysis of corn stalks with alkali-fused fly ash (AFFA) at 200 and 600 & DEG;C (denoted as AFFA/BC). The Pb(II) adsorption mechanism and adsorption performance were investigated. The AFFA/BC had larger specific surface areas than the pure BC samples (2.54-137 vs. 0.50 m(2) g(-1)) owing to their stable carbon structure. The Pb(II) adsorption capacity of AFFA/BC in water was approximately 6% higher than that of BC owing to the increased cation (Na+) exchange and new bonding sites, such as C-O and Si-O. AFFA/BC exhibited good Pb(II) adsorption performance in high-concentration simulated wastewater (pH 4-6), with a maximum adsorption capacity of 110.29 mg g(-1). The Pb(II) adsorption mechanism was in accordance with the pseudo-second-order kinetic and Langmuir isotherm models. At 25 & DEG;C and pH 5, the theoretical Pb(II) adsorption capacities of AFFA(200)/BC and AFFA(600)/BC were 201.66 and 186.81 mg g(-1), respectively, compared to 145.98 mg g(-1) of BC. Physical adsorption, precipitation, cation exchange, and complexation were identified as the main Pb(II) adsorption mechanisms through X-ray photoelectron spectrometry.

Automated summary

This study investigated the potential of alkali-fused fly ash as a modifier for biochar and found that the modified biochar exhibited improved Pb(II) adsorption capacity. The modification process increased the specific surface area and introduced new bonding sites, leading to enhanced cation exchange and Pb(II) adsorption performance. The modified biochar also demonstrated good adsorption performance in high-concentration simulated wastewater. The Pb(II) adsorption mechanism was found to involve physical adsorption, precipitation, cation exchange, and complexation.