In situ fabrication of hierarchical biomass carbon-supported Cu@CuO–Al2O3 composite materials: synthesis, properties and adsorption applications

Abstract

Hierarchical Cu–Al₂O₃/biomass-activated carbon composites were successfully prepared by entrapping a biomass-activated carbon powder derived from green algae in the Cu–Al₂O₃ frame (H–Cu–Al/BC) for the removal of ammonium nitrogen (NH₄⁺-N) from aqueous solutions. The as-synthesized samples were characterized via XRD, SEM, BET and FTIR spectroscopy. The BET specific surface area of the synthesized H–Cu–Al/BC increased from 175.4 m² g⁻¹ to 302.3 m² g⁻¹ upon the incorporation of the Cu–Al oxide nanoparticles in the BC surface channels. The experimental data indicated that the adsorption isotherms were well described by the Langmuir equilibrium isotherm equation and the adsorption kinetics of NH₄⁺-N obeyed the pseudo-second-order kinetic model. The static maximum adsorption capacity of NH₄⁺-N on H–Cu–Al/BC was 81.54 mg g⁻¹, which was significantly higher than those of raw BC and H–Al/BC. In addition, the presence of K⁺, Na⁺, Ca²⁺, and Mg²⁺ ions had no significant impact on the NH₄⁺-N adsorption, but the presence of Al³⁺ and humic acid (NOM) obviously affected and inhibited the NH₄⁺-N adsorption. The thermodynamic analyses indicated that the adsorption process was endothermic and spontaneous in nature. H–Cu–Al/BC exhibited removal efficiency of more than 80% even after five consecutive cycles according to the recycle studies. These findings suggest that H–Cu–Al/BC can serve as a promising adsorbent for the removal of NH₄⁺-N from aqueous solutions.