Development of functionalized biochar composites for enhanced boron adsorption from aqueous solutions

This study focuses on developing biochar-based adsorbents with high adsorption capacity and rapid adsorption rates for removing boron from aqueous solutions. Hydroxy-enriched biochar composites (BC (carboxylated biochar), BC-PDA (polydopamine loaded biochar), MBC-PDA (polydopamine loaded magnetic biochar), BC-AlOOH (AlOOH loaded biochar), and BC-ZnCl₂ (biochar modified by ZnCl₂)) were synthesized specifically for boron adsorption to utilize the superior adsorption capacity of biochar. All adsorbents were synthesized using straightforward experimental techniques from date palm cellulosic fibers as promising lignocellulose feedstock and subjected to various characterization methods. Boron adsorption kinetics, isotherms, mechanism, and adsorbent recycling were investigated using batch adsorption experiments. The experimental results showed adsorption capacity values of 14, 20.5, 21.5, 43.2, and 44.2 mg/g for BC, BC-PDA, MBC-PDA, BC-AlOOH, and BC-ZnCl₂ composites at 360 min. The prominent adsorption capacity of the synthesized adsorbents was related to the abundant existence of -OH functional groups on the BC adsorbent surface and the abundance of pores widely distributed throughout the surface, facilitating the chemical and physical adsorption of boron. The synthesized adsorbents exhibited a promoted boron adsorption capacity and ease of recovery and reusability.