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ABSTRACT FEI, XIUZHU. Towards Closed Loop

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ABSTRACT FEI, XIUZHU. Towards Closed Loop Recycling of Polyester Fabric. (Under the direction of Dr. Harold S. Freeman and Dr. David Hinks). Polyethylene terephthalate (PET) is extensively used in various types of apparel, home textiles, and outdoor products that are regularly placed in landfills after use. But unlike natural fibers, PET is not readily biodegradable. In view of sustainability, research regarding the recycling of textiles derived from PET fibers is of interest, and effective color removal has been recognized as a crucial step towards recycling of colored PET fabrics. To this end, a decolorization process was developed using sodium formaldehyde sulfoxylate (SFS) as the reducing agent. Disperse dye decolorization studies were conducted in water and acetone media, and an optimized combination of treatment time (30 min), water to acetone ratio (1:2), SFS concentration (10g/L), temperature (100oC), and liquor ratio (1:50) was found effective for decolorizing various commercial disperse dyes as well as basic dyes. Results in terms of intrinsic viscosity of decolorized PET showed that the optimized SFS decolorization method has no significant effect on fiber strength. The goal of this work was to study the recyclability of bath and fabric after decolorization, investigate the ecotoxicity of the decolorization process, study the life cycle assessment of the closed-loop recycling process, characterize dyes from commercial fabrics and study their decolorization properties. Fabric decolorization using the optimized SFS method followed by re-dyeing using Disperse Yellow 42, Disperse Orange 30, Disperse Red 60, and Disperse Blue 79 was conducted on cationic dyeable PET. It was found that fabrics containing nitro and anthraquinone dyes, Disperse Yellow 42 and Disperse Red 60, respectively, have better decolorization efficiency than those containing azo Disperse Orange 30 and Disperse Blue 79 dyed fabrics. Bearing in mind that ecotoxicity testing is of increasing importance in the screening of newly developed substances or treatment processes, solutions of six high volume disperse dyes and one basic dye were decolorized using SFS, and the resultant solutions were tested with Daphnia similis and Parhyale hawaiensis to observe the acute toxicity to the two species. The control sample, which is the SFS solution without dyes, showed that EC50 to Daphnia similis is 1.83%, and LC50 to Parhyale hawaiensis is 9.0%. EC50 and LC50 were expressed in percentage of dye solution. Decolorized dye solutions differed in the toxicity, however, the differences were not significant. The toxicity observed in the acute tests is probably mainly related to SFS decolorization medium. Converting EC50 and LC50 of decolorized solution to equivalent concentration, the effluents were considered relatively harmful to Daphnia similis. Control SFS solution and decolorized Disperse Blue 56 were moderately toxic to Parhyale hawaiensis, whereas decolorized Disperse Orange 30 was relatively nontoxic to Parhyale hawaiensis. A closed loop recycling of PET fabric was proposed beginning with collection of post- consumer PET fabrics/garments, followed by chemical decolorization, mechanical reprocessing, and ending with production of recycled PET fibers. A life cycle assessment was conducted to compare the innovative closed loop recycling process and virgin PET production process. Results suggest that recycled PET production has less environmental impacts than the virgin system in six categories, namely, exotoxicity, eutrophication, human health- carcinogenics, human health-non-carcinogenics, ozone depletion, and respiratory effects, but also shows higher impact results in four categories, which are acidification potential, global warming potential, photochemical ozone formation potential, and fossil fuels resource depletion. Contribution analysis shows higher impacts in those four categories result from the consumption of acetone. Sensitivity analysis also shows that overall impact is sensitive to acetone consumption, which means environmental benefits of the recycling method are highly dependent on the acetone consumptions. This life cycle assessment is conducted based on a hypothetical closed-loop scenario. Further work on obtaining specific data in innovative recycling processing for more reliable analysis would be beneficial. © Copyright 2018 by Xiuzhu Fei All Rights Reserve Towards Closed Loop Recycling of Polyester Fabric by Xiuzhu Fei A dissertation submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Fiber and Polymer Science Raleigh, North Carolina 2018 APPROVED BY: _______________________________ _______________________________ Dr. David Hinks Dr. Harold S Freeman Co-chair of Advisory Committee Co-chair of Advisory Committee _______________________________ _______________________________ Dr. Nelson Vinueza Dr. Joseph DeCarolis ii DEDICATION I dedicate my dissertation work to Dr. Harold S. Freeman and Dr. David Hinks for their guidance and support over the years. I also dedicate this work to my parents, my sister, brother in law, and my beloved, Ju Dong. iii BIOGRAPHY Xiuzhu Fei was born in Shaoxing, Zhejiang Province of China in 1991. Shaoxing is a medium size city that relied heavily on textile industry 15 years ago. Many of her relatives were working for textile companies. However, due to the increasing regulations and restrictions, the traditional labor-intensive textile plants and mills lost their competitiveness in recent years. She chose the Dyeing and Finishing Engineering as her major in Jiangnan University, because she wanted to learn more about textiles and bring some benefits to her hometown. Later she was enrolled to North Carolina State University in August 2013 as a master student majoring in Textile Chemistry. Afterwards she was enrolled in the Fiber and Polymer Science Program to pursue a PhD degree. She believes sustainable textiles are the future of the textile world. iv ACKNOWLEDGMENTS Writing this note of thanks is the finishing touch on my dissertation. It has been several years of learning in North Carolina State University, Raleigh, not only in the scientific area, but also on a personal level. I would like to express my sincere acknowledgements to the people who have supported and helped me so much throughout this period. I would first like to thank Dr. David Hinks for founding me throughout my research career. I have never imaged I could study abroad before I received an offer letter from Dr. Hinks 5 years ago. I am deeply grateful for the opportunity. He covered me all the time so I could focus on the research. Without his support, this PhD work would not have been achievable. My greatest appreciation goes to Dr. Harold S. Freeman for all the guidance, instruction and encouragement he gave me during the time I spent at the NC State. He is a very patient and responsible professor. I will always keep every piece of hand-written feedback he gave to me about my thesis and manuscripts. He pointed me to the right direction so that I can successfully complete my dissertation. He is also a considerate person which inspires me a lot in my personality. I would also like to thanks Dr. Nelson Vinueza and Dr. Joseph DeCarolis for their excellent cooperation as kindly being my committee members. I sincerely appreciate the helpful suggestions and comments I received from them. A very special thanks to previous and current group members in Dr. Hinks’s and Dr. Freeman’s research group, especially Dr. Malgorzata Szymczyk, for their help in the lab work and for their companionship in my life. v Finally, many thanks go to my parents, sister and brother in law, for believing in me and supporting me all the time; to all my dear friends for bringing me happiness and joy; and to my dear boyfriend Ju, for his selfless love. vi TABLE OF CONTENTS LIST OF TABLES .............................................................................................................. x LIST OF FIGURES ..........................................................................................................xii 1. INTRODUCTION ............................................................................................................. 1 2. LITERATURE REVIEW .................................................................................................. 3 2.1 Polyethylene terephthalate ........................................................................................... 3 2.1.1 Introduction to polyethylene terephthalate ............................................................. 3 2.1.2 Properties of polyesters ......................................................................................... 5 2.2 Coloration of polyester ................................................................................................ 7 2.2.1 Disperse dyes ........................................................................................................ 8 2.2.2 Basic dyes ........................................................................................................... 14 2.3 Dye characterization .................................................................................................. 16 2.3.1 Ultraviolet-visible spectroscopy .......................................................................... 16 2.3.2 Chromatography ................................................................................................. 17 2.3.3 Mass spectrometry
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