Study on the hydrogen production promotion effect and immobilization mechanisms of copper during the pyrolysis process of waste cotton textiles

Landfilling waste textiles causes a waste of resources. Copper is the main metal in waste textiles, and it is one of the widely used pyrolysis catalysts. This research investigated the role of copper during the pyrolysis process of waste cotton textiles, including the promoting effect on hydrogen generation and its immobilization in biochar. The pyrolysis experiment was conducted on waste pure cotton textiles impregnated with different concentrations of copper nitrate solutions. The experimental results showed that the addition of copper increased the hydrogen concentration by 121%, while the pyrolysis process reduced the copper leaching rate by 57.5%. Hydrogen concentration increased by 123% as the temperature increased, but the high temperature would affect the immobilization of copper. Hydrogen production and copper immobilization could be improved simultaneously around 700 celcius. The gas evolution was monitored by TG-MS and the biochar was characterized by XRD, FTIR, and XPS. The results indicated that the complexation of oxygen-containing functional groups and the generation of metallic copper decreased the leaching of copper, the heterostructure of copper on the surface of biochar catalyzed the secondary cleavage of organic fraction, increasing the production of hydrogen. The mechanism of hydrogen generation involved the decomposition of cellulose, the cleavage of organic macromolecules, and the secondary reaction of small molecule gases.