Ball milling-assisted synthesis of attapulgite-rice husk biochar composites for efficient formaldehyde removal: Experimental and computational insights

Abstract

This study explores the Ball milling-assisted synthesis of attapulgite-rice husk biochar composites (5 %ATP/BBC) to remove formaldehyde (HCHO) efficiently. The composite was fabricated to enhance surface area and increase exposure to functional groups, which are crucial for adsorption. The experimental findings showed that 5 %ATP/BBC effectively removes HCHO, with a maximum theoretical static adsorption capacity of 0.260 mg/g and a dynamic adsorption capacity of 141.048 mg/g, surpassing both BBC500 and BC500. Chemical adsorption was the predominant process, and the adsorption followed pseudo-second-order kinetics. Further X-ray photoelectron spectroscopy (XPS) analysis indicated that formaldehyde molecules were incorporated onto the biochar surface, as evidenced by changes in C=O and C–C bonds. Molecular-level investigations through density functional theory (DFT) and Bader charge analysis revealed that adsorption involves charge redistribution, with ATP playing a key role as an active site. These findings were confirmed by charge density difference (CDD) analysis, which demonstrated charge transfer during adsorption. The results show that 5 % ATP/BBC can be a sustainable and practical material for HCHO removal, offering valuable insights into developing advanced adsorbents for environmental applications.