Novel nanomagnetite doped sugarcane bagasse biochar biocomposite for efficient removal of toxic heavy metal ions from wastewater

Abstract

Efficient enrichment and remediation of heavy metals from real wastewater and contaminated soil, both of which frequently contain high concentrations of competing ions, remain significant challenges. Producing advanced carbon-based materials that efficiently remove contaminants from water is crucial for environmental remediation and public health. This investigation describes the concurrent activation and magnetization processes used to synthesize Mag@SAC, a magnetic sugarcane activated carbon, from carbonized sugarcane bagasse (SB) using Fe³⁺ and Fe²⁺ ions. The Mag@SAC biocomposite was thoroughly characterized using Brunauer–Emmett–Teller (BET) and N₂ adsorption isotherm analysis, point of zero charge (pH_PZC), elemental analysis, Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Thermogravimetric analysis (TGA). The as-prepared Mag@SAC was applied to remove toxic heavy metals, Pb²⁺ and Hg²⁺ from solutions, with easy separation achieved by simply applying an external magnet. The adsorption of Pb²⁺ and Hg²⁺ onto Mag@SAC biocomposite follows pseudo-second-order (PSO) kinetics and is best described by the Langmuir isotherm, indicating spontaneous, monolayer chemisorption. This process is supported by a high correlation coefficient (R² ≥ 0.999) and low error functions. Maximum adsorption capacities of 90.82 mg g⁻¹ for Pb²⁺ and 164.20 mg g⁻¹ for Hg²⁺ were obtained under optimal conditions. Thermodynamic analysis indicates that the adsorption of Hg²⁺ onto Mag@SAC is spontaneous and endothermic, whereas the adsorption of Pb²⁺ is spontaneous and exothermic. The Mag@SAC biocomposite can be successfully regenerated up to the 5^th cycle. The mechanisms of adsorption of Pb²⁺ and Hg²⁺ onto the Mag@SAC were elucidated.