화학공학소재연구정보센터
Process Safety and Environmental Protection, Vol.139, 315-324, 2020
Novel pre-treatment of dirty post -consumer polyethylene film for its mechanical recycling
The excessive consumption of plastic films in many applications due to their lightness and versatility and the low recycling rate of this type of material is a very significant matter that increases the problem of plastic film pollution. Plastic recycling has been a popular topic in conferences and technical jour- nals during the past few years, but studies on the washing process are rarely published. Washing is an essential step in the mechanical recycling of these materials. This work provides an assessment on the feasibility of the washing procedure to clean post -consumer polyethylene film, presented in municipal solid waste, which had not been collected selectively, to increase mechanical recycling of post -consumer plastic films. Particularly, the study analyses (1) the characteristics of the washing water after cleaning procedure at room temperature, at 60 ? C and at 60 ? C with addition of NaOH chemical; (2) benefits of a drying stage before washing on the cleaning efficiency and characteristics of residual water and (3) benefits of physical or physical -chemical treatment of water by using a single step of settling or a two- step process that includes flocculation -coagulation and later settling, in the possibility of wastewater recycling for its use again in the washing process. Results showed very low differences between washing procedures at room temperature and at 60 ? C. However, with the addition of NaOH chemical best clean- ing was achieved although a more difficult wastewater treatment was found, due to high COD, BOD 5 , chlorides, nitrogen and phosphorous content. Results also showed that drying before washing signifi- cantly improved decontamination of post -consumer polyethylene film decreasing the consumption of fresh water and the requirement of depuration of it. Finally, the stage of physical -chemical treatment of wastewater by means of the use of coagulants and flocculants showed the possibility of increasing the reuse of water in the process for cleaning of plastic with relatively low cost. ? 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.