Study on Fenton-based discoloration of reactive-dyed waste cotton prior to textile recycling

The aim of this study is to investigate the feasibility of an alternative Fenton-based advanced oxidation process for the discoloration of reactive-dyed waste cotton as a pre-treatment for textile recycling. For that, pre-wetted dark-colored (black and blue) knitted samples of 300 cm² are treated in 1200mL Fenton-solution containing 14 mM Fe²⁺ and 280mM H₂O₂ at 40 °C. Characterization of the textiles before and after the treatments are performed by UV VIS-spectrophotometry measuring color strength, microscopy, FTIR spectroscopy, thermal analysis and tensile testing measuring tenacity and elongation. Afterwards, the cotton is mechanically shredded for qualitative analysis of the recyclability. The color-strength measurements of the black and blue cotton led to discoloration-efficiencies of respectively 61.5 and 72.9%. Microscopic analysis of discolored textile fabric also showed significant fading of the colored textiles. Mechanical analysis resulted in reduced tensile strength after treatment, indicating oxidation of the cellulosic structure besides the degradation of the dye-molecules, also confirmed by reductions in thermal stability found after thermal analysis. Shredding of the fabric resulted in enhanced opening, but shorter remaining fibers after treatment. The findings of this study provide a proof-of-concept for an alternative color-stripping treatment concerning a Fenton-based advanced oxidation process as a pre-treatment for textile recycling.