Facile One-Step Pyrolysis of ZnO/Biochar Nanocomposite for Highly Efficient Removal of Methylene Blue Dye from Aqueous Solution

In this work, we developed a facile one-step pyrolysismethod forpreparing porous ZnO/biochar nanocomposites (ZBCs) with a large surfacearea to enhance the removal efficiency of dye from aqueous solution.Peanut shells were pyrolyzed under oxygen-limited conditions witha molten salt ZnCl2, which played the roles of the activatingagent and precursor for the formation of nanoparticles. The effectsof the mass ratio between the molten salt ZnCl2 and peanutshells as well as pyrolysis temperature on the formation of ZBCs wereinvestigated. Characterization results revealed that the as-synthesizedZBCs exhibited a highly porous structure with a specific surface areaof 832.12 m(2)/g, suggesting a good adsorbent for efficientremoval of methylene blue (MB). The maximum adsorption capacity ofZBCs on MB was 826.44 mg/g, which surpassed recently reported adsorbents.The formation mechanism of ZnO nanoparticles on the biochar surfacewas due to ZnCl2 vaporization and reaction with water moleculesextracted from the lignocellulosic structures. This study providesa basis for developing a simple and large-scale synthesis method forwastewater with a high adsorption capacity.