Structural characteristics, surface properties and methylene blue adsorption application of halloysite nanotubes regulated with controllable treatment processes

• Systematic comparison of five treatment strategies reveals that acid treatment of calcined HNTs maximizes methylene blue adsorption by increasing specific surface area while preserving tubular structure. • Optimal treatment (pre-calcination at 600°C for 3 h followed by acid treatment at 60°C for 8 h) yields a specific surface area of 443 m²·g⁻¹ and an adsorption capacity of 190 mg·g⁻¹. • Calcination temperature inversely affects MB reactivity, while moderate acid treatment enhances adsorption by expanding the lumen and reducing surface potential. • Kinetic and Arrhenius analyses confirm that chemical reactions govern acid/alkali interactions with HNTs, providing a basis for controlled structure regulation.