Effective conversion of waste polyester–cotton textile to ethanol and recovery of polyester by alkaline pretreatment

• A cotton–polyester waste textile was pretreated with alkaline solvent at various conditions.
• Pretreatment increased the glucose and ethanol yields from the textile.
• The properties of recovered polyester evaluated by FTIR, DSC and viscosity analyses.
• The pretreatment resulted in a minor change on the properties of polyester.

The majority of textiles typically contain a biodegradable part that is cellulose and a non-biodegradable part which is a polyester. In this study, alkali pretreatment was evaluated for improvement of ethanol production from the cellulose part of a polyester–cotton textile and recovery of the polyester. The pretreatment was conducted by different alkali solutions of NaOH (12 wt%), NaOH/urea (7/12 wt%), NaOH/thiourea (9.5/4.5 wt%) and NaOH/urea/thiourea (8/8/6.4 wt%) at −20, 0, 23, and 100 °C for 1 h. All of the pretreatments resulted in improvement of enzymatic hydrolysis yield to over 88%, while it was only 46.3% for the untreated textile. The best hydrolysis results were observed by the pretreatments at the reduced temperatures (−20 and 0 °C). The maximum yield of ethanol production from the textile by simultaneous saccharification and fermentation was 70%, obtained after the pretreatment with NaOH/urea at −20 °C whereas it was only 36% for the untreated textile. The polyester part of the textile was recovered after the hydrolysis of the cellulosic part and its properties were studied by FTIR, Differential Scanning Calorimetry (DSC), and viscosity measurements and compared with the untreated polyester used in the textile. The results showed that the alkaline pretreatment followed by hydrolysis resulted in recovery of 98% of the polyester without significant change in its properties.

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