A novel strategy utilizing wool waste to prepare carbonized porous C/N/O co-doped TiO ₂ composites for enhancing adsorption and photocatalytic degradation of organic pollutants

The extensive production of waste wool in the textile industry poses significant environmental challenges. To address this issue, we present a novel recycling approach that transforms waste wool into a carbonized, porous, and C/N/O co-doped TiO 2 composite material. This was achieved through a simple one-step hydrothermal synthesis followed by calcination in either a nitrogen or an air atmosphere. This innovative method not only repurposes waste wool but also creates a material with impressive adsorption and photocatalytic properties, offering a new solution for environmental remediation. The calcination process effectively dispersed TiO 2 nanoparticles, increasing the number of active sites. When calcined in a nitrogen atmosphere, the graphitization of wool biochar was enhanced, nitrogen doping of TiO 2 was achieved, and oxygen vacancies were created, all of which significantly improved the adsorption performance. The resulting composite exhibited an adsorption capacity for methylene blue dye that was 13.8 times higher than that of the untreated sample, and 9.9 times higher than that of the sample calcined in air. Furthermore, the composite retained 99% of its original adsorption capacity after a second calcination cycle, indicating strong recycling potential. Photocatalytic performance tests showed a marked improvement in the degradation efficiency of methylene blue, Congo red, and tetracycline hydrochloride under simulated solar irradiation. The primary active species involved were singlet oxygen ( 1 O 2 ) and photogenerated holes (h + ), while superoxide radicals ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:mo>⋅</mml:mo> <mml:msubsup> <mml:mrow> <mml:mtext>O</mml:mtext> </mml:mrow> <mml:mn>2</mml:mn> <mml:mo>−</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> ) and hydroxyl radicals (‧OH) also contributed to the photodegradation of methylene blue. The use of wool waste as a catalyst support material not only extends its practical applications but also helps reduce the environmental impact of organic pollutants.