Separation And Recycling Of Waste Polyester/Cotton Blended Fabric And Preparation Of Cellulose Acetate

Environmental pollution has always been an unavoidable problem in the development of modern civilization,and it has been destroying the ecosystem on the earth and making our living environment worse.With the growth of world population and the shortening of fashion cycle,the demand for textiles increases year by year,which makes more and more waste textiles.Waste textiles are mainly blended fabrics,among which polyester/cotton blended fabrics are the most common.Due to the special structure of the blended fabric,it is necessary to separate polyester and cotton fiber before recycling.Strong acids,such as H₂SO₄,are often used to separate polyester/cotton blended fabric,which leads to corrosion of equipment and environmental pollution.Phosphotungstic acid?HPW?is a recyclable heteropoly acid,which has been studied in the field of cellulose hydrolysis.HPW can be used to hydrolyze cotton fiber to separate polyester/cotton fabric and avoid secondary pollution.The aim of this paper was to establish a set of recovery method for polyester/cotton blended fabric.In this paper,the hydrolysis process of pure cotton fabric catalyzed by HPW was studied.The effects of reaction temperature,reaction time,HPW concentration,and solid-liquid ratio on the yield and crystallinity of microcrystalline cellulose?MCC?were investigated.The hydrolysis mechanism of cotton fiber catalyzed by HPW was studied.On this basis,the effects of reaction temperature,reaction time,HPW concentration and solid-liquid ratio on the yields of polyester and cotton fiber were investigated,and the optimal separation conditions were determined.Furthermore,the effect of separation treatment on polyester and cotton fiber was investigated.Finally,cellulose acetate?CA?was prepared by acetylation of MCC with ferric chloride.Terephthalic acid?TPA?was prepared from recycled polyester by neutral hydrolysis and purified by DMF cooling crystallization.CA and TPA were characterized and compared with commercial grade products respectively.The results show that:?1?MCC was prepared by hydrolysis of waste cotton fabric with HPW.The yield and crystallinity of MCC were as high as 83.4%and 85.2%,respectively.The optimum process conditions were HPW concentration of 3.47mmol/L,reaction temperature of 140?,reaction time of 6 h,and solid-liquid ratio of 1:40.After hydrolysis,MCC was still cellulose type I,and exhibited better performance than commercial MCC such as a higher crystallinity,smaller particle size?20.37?m?,and narrower particle size distribution?72.75%,8.68–31.1?m?.In addition,HPW could be extracted and recycled,and the activity of recovered HPW remained unchanged.?2?HPW was used to separate waste polyester/cotton blended fabric.The optimum separation conditions were determined as follows:HPW concentration of 3.47 mmol/L,a solid/liquid ratio of 1:20,reaction temperature of 140?,and reaction time of 6 h.The yields of MCC and polyester were as high as 85.12%and 99.77%,respectively.HPW could be recycled,and the activity of recovered HPW remained unchanged.The separation treatment hydrolyzed the cotton fiber into MCC,and reduced the crystallinity and mechanical properties of polyester.?3?Cellulose acetate?CA?was prepared by acetylation of MCC with ferric chloride.The optimum process conditions were 0.5 g MCC,0.1 g ferric chloride,reaction temperature 50?,reaction time 40 min,5 mL glacial acetic acid,and 5mL acetic anhydride.The performance of CA was similar to that of commercial CA,which had application value.?4?TPA was separated and purified by cooling crystallization.The effect of dissolution temperature/crystallization temperature on the yield of TPA was investigated,and the suitable crystallization conditions were determined as90?/30?.The purity of purified TPA was as high as 98.65%,which met the quality standard of TPA.