Separation of waste polyester/cotton blended fabrics by phosphotungstic acid and preparation of terephthalic acid

Abstract

In order to recycle waste polyester/cotton blended fabrics (WBFs), an environmentally friendly process was designed for separating WBFs with phosphotungstic acid (H3PW12O40, HPW). Polyester and microcrystalline cellulose (MCC) were obtained after the process and the polyester was further degraded into terephthalic acid (TPA) by neutral hydrolysis. The effects of separation conditions were investigated, and the optimum conditions were determined as follows: HPW concentration of 3.47 mmol/L, a solid/liquid ratio of 1:20, reaction temperature of 140 °C, and reaction time of 6 h. Under the optimum conditions, the yields of polyester and MCC were 99.77% and 85.12%, respectively. HPW could be extracted and recycled easily with diethyl ether without affecting the yields of polyester and MCC. In addition, the separated polyester, MCC and prepared TPA were characterized. The results showed that the crystallinity of polyester decreased, and the cotton was hydrolyzed to MCC after the separation treatment. TPA was prepared with a high purity of 99.92%, and exhibited high crystallinity, favorable thermal stability, and small particle size.