Ball-milled dysprosium oxide loaded biochar-montmorillonite composite for efficient removal and great recycling performance of cationic organic pollutants

New and sustainable approaches for the removal of cationic organic pollutants, such as methyl violet (MV) and methylene blue (MB) dyes, from aqueous solutions are needed. In this study, hickory wood was pyrolyzed with montmorillonite and then ball milled with dysprosium oxide at 350 rpm for 3 h, without any use of toxic compounds. The resulting composite was rich in oxygen-containing functional groups (e.g., carboxyl and hydroxyl), had uniform lamellar-porous micromorphology and a surface area (88.9 m 2 g −1 ) 2.5 times that of the original biochar. The composite exhibited excellent removal of aqueous methylene blue (113.6 mg g −1 ) and methyl violet (107.6 mg g −1 ), which was approximately 6.6 and 2.6 times that of the biochar. Modeling and characterization results suggest that the adsorption of cationic organic pollutants on the composite was controlled by multiple mechanisms including electrostatic attraction, hydrogen bonding, ion exchange, and surface complexation. After five regenerations, the composite maintained methylene blue (87.4 %) and methyl violet (84.8 %) removal ability, thus demonstrating good stability and reusability potential. These findings highlight the advantages and potential of ball-milled dysprosium oxide-loaded-biochar-montmorillonite composite for water treatment and environment remediation.