Extraction and Reuse of Disperse Dyes from Polyethylene Terephthalate (PET) Fabric in a Subsequent Dyeing Process

Current recycling processes for dyed polyester textiles primarily focus on recovering the PET substrate, while the disperse dye retained within the polymer structure is generally overlooked and consequently lost as a potentially reusable resource. This study investigated the recovery and reuse of both disperse dyes and poly(ethylene terephthalate) (PET) from dyed fabric, with the aim of improving resource utilization and supporting the development of more sustainable textile recycling processes. Virgin PET (V_PET) was dyed with C.I. Disperse Blue 79.1 and C.I. Disperse Red 343, followed by extraction using chlorobenzene and dimethyl sulfoxide (DMSO). FTIR and 1H NMR analyses showed that fractions recovered by chlorobenzene extraction retained the principal FTIR and proton NMR spectral features of the purified reference dyes and were therefore chosen for further study. Chlorobenzene extraction at 100 °C for 2 h was selected based on dye removal and retention of fabric properties. Bursting strength of the fabric decreased after dyeing and further decreased after chlorobenzene extraction. V_PET showed a bursting strength of 691 N, which decreased by approximately 1–3% after dyeing. The greatest reduction was observed for the Disperse Blue-dyed fabric extracted at 120 °C, with a bursting strength of 616 N. Crystallinity also decreased from 44.41% for V_PET to approximately 35–36% for polyester fabrics after dye extraction (R_PET). The R_PET retained whiteness indices of 71–72 and could be successfully redyed, exhibiting higher color strength than V_PET. The recovered disperse dyes could be reused for PET dyeing. These results demonstrate the potential of disperse dye extraction for recovering both the dye and PET substrate.