Preparation of KMnO₄ modified N-doped bamboo biochar by microwave pyrolysis for enhancing heavy metals adsorption...

Heavy metals in aqueous solutions have a remarkable environmental toxicity, making their remediation an urgent priority. Recent research indicates that modifying biochar significantly improves its ability to remove heavy metals from aqueous solutions. Thereby, we utilized potassium permanganate (KMnO₄) modification to further enhance the adsorption efficiency of KMnO₄-modified nitrogen-doped bamboo biochar (MNBB), specifically targeting Zn²⁺ and Cu²⁺. The resulting MNBB exhibited a high specific surface area (613.78 m²/g) and a rich abundance of surface functional groups. Batch adsorption experiments and comprehensive characterizations revealed excellent adsorption capacities, with a maximum capacity of 83.96 mg/g for Zn²⁺ and 141.24 mg/g for Cu²⁺, representing enhancements of 39 % and 60 % over NBB, respectively. The removal efficiency of Zn²⁺ and Cu²⁺ could still be maintained at 35.39 % and 54.12 %, respectively, after five adsorption-desorption cycles. The adsorption data were fitted by kinetics and isotherm models, indicating that the adsorption process was mainly explained by monolayer adsorption and chemical adsorption. The dominant adsorption mechanisms were identified as cation-π interactions, surface complexation, precipitation, and adsorption-reduction interactions. This research offers crucial theoretical understanding and practical guidance for effectively utilizing biomass resources and employing modified biochar to remove heavy metals from water systems.