In Situ Ca‐ and Mg‐ Codoped Biochar Derived from Tobacco Stem for Phosphate Adsorption and Desorption

Abstract

Phosphorus is an important element for plant growth. The efficient use and recovery of phosphorus is crucial due to limited phosphate resource reserves. This study explored the potential application of an in situ Ca and Mg co‐doped biochar derived from tobacco stem to reclaim and reuse phosphate from aqueous solutions. We performed various batch adsorption experiments and industrial analysis based on different parameters. The findings indicate that biochar prepared using the raw material particle size range of 0.85–2 mm and pyrolyzed at 800 °C presented good pore structure and specific surface area. Ca and Mg elements in biochar exhibited great influence on its phosphate adsorption property. The maximum phosphate adsorption capacity of the tobacco stem‐based biochar was 54.66 mg/g, and the experimental data agreed with the Langmuir equation, suggesting monolayer adsorption. The adsorption process conformed to the pseudo‐second‐order kinetic equation, indicating that chemisorption was the dominant adsorption process and that the adsorption was controlled by intra‐particle diffusion. Furthermore, phosphate adsorbed on tobacco stem‐based in situ Ca and Mg co‐doped biochar was released under acidic, alkaline, and neutral conditions. Therefore, in situ Ca and Mg co‐doped biochar prepared from tobacco stems is a potential environmentally friendly and low‐cost adsorbent for phosphorus recovery.