Development of a new approach based on midwave infrared spectroscopy for post-consumer black plastic waste sorting in the recycling industry.

Waste sorting is key to the process of waste recycling. Exact identification of plastic resin and wood products using Near Infrared (NIR, 1-1.7µm) sensing is currently in use. Yet, dark targets characterized by low reflectance, such as black plastics, are hard to identify by this method. Following the recent success of Midwave Infrared (MWIR, 3-12µm) measurements to identify coloured plastic polymers, the aim of this study was to assess whether this technique is applicable to sorting black plastic polymers and wood products. We performed infrared reflectance contact measurements of 234 plastic samples and 29 samples of wood and paper products. Plastic samples included black, coloured and transparent Polyethylene Terephthalate (PET), Polyethylene (PE), Polyvinyl Chloride (PVC), Polypropylene (PP), Polylactic acid (PLA) and Polystyrene (PS). The spectral signatures of the black and coloured plastic samples were compared with clear plastic samples and signatures documented in the literature to identify the polymer spectral features in the presence of coloured material. This information was used to determine the spectral bands that best suit the sorting of black plastic polymers. The main NIR-MWIR absorption features of wood, cardboard and paper were identified as well according to the spectral measurements. Good agreement was found between our measurements and the absorption features documented in the literature. The new approach using MWIR spectral features appears to be useful for black plastics as it overcomes some of the limitations in the NIR region to identify them. The main limitation of this technique for industrial applications is the trade-off between the signal-to-noise ratio of the sensor operating in standoff mode and the speed at which waste is moved under the sensor. This limitation can be resolved by reducing the system's spectral resolution to 16cm-1, which allows for faster spectra acquisition while maintaining a reasonable signal-to-noise ratio.

[1]  C. Wilcox,et al.  Plastic waste inputs from land into the ocean , 2015, Science.

[2]  Giorgia Foca,et al.  Efficient chemometric strategies for PET–PLA discrimination in recycling plants using hyperspectral imaging , 2013 .

[3]  Offer Rozenstein,et al.  A review of progress in identifying and characterizing biocrusts using proximal and remote sensing , 2017, Int. J. Appl. Earth Obs. Geoinformation.

[4]  J. Baeyens,et al.  Recycling and recovery routes of plastic solid waste (PSW): a review. , 2009, Waste management.

[5]  Florent Prel,et al.  A broadband field portable reflectometer to characterize soils and chemical samples , 2013, Defense, Security, and Sensing.

[6]  G. B. B. M. Sutherland,et al.  Infrared Spectra of High Polymers. II. Polyethylene , 1956 .

[7]  M. Prasad,et al.  Negative thermal coefficient behaviour, dielectric and mechanical properties of poly(vinyl chloride)/poly(vinyl alcohol) blends , 2016 .

[8]  Silvia Serranti,et al.  Application of NIR hyperspectral imaging for post-consumer polyolefins recycling , 2012, Other Conferences.

[9]  N. H. Zhurok.  ADAPTATION OF UKRAINIAN LEGISLATION TO THE EU STANDARDS: ANALYSIS DIRECTIVE 2008/98/EC ON WASTE AND REPEALING CERTAIN DIRECTIVES , 2019, Comparative-analytical law.

[10]  Nizar Haoues,et al.  State of the art of plastic sorting and recycling : Feedback to vehicle design , 2007 .

[11]  E. Smidt,et al.  Classification of waste materials using Fourier transform infrared spectroscopy and soft independent modeling of class analogy. , 2008, Waste management.

[12]  Abraham Vázquez-Guardado,et al.  Multi-spectral infrared spectroscopy for robust plastic identification. , 2015, Applied optics.

[13]  James A. Gardner,et al.  MODTRAN5: a reformulated atmospheric band model with auxiliary species and practical multiple scattering options , 2004, SPIE Asia-Pacific Remote Sensing.

[14]  Samuel Krimm,et al.  Infrared spectra of high polymers , 1960 .

[15]  Silvia Serranti,et al.  An innovative recycling process to obtain pure polyethylene and polypropylene from household waste. , 2015, Waste management.

[16]  Satoru Tsuchikawa,et al.  A Review of Recent Near Infrared Research for Wood and Paper , 2007 .

[17]  L. Hanssen,et al.  Wavenumber Standards for Mid‐infrared Spectrometry , 2006 .

[18]  Silvia Serranti,et al.  Upgrading of PVC rich wastes by magnetic density separation and hyperspectral imaging quality control. , 2015, Waste management.

[19]  José Manuel Amigo,et al.  Hyperspectral image analysis. A tutorial. , 2015, Analytica chimica acta.

[20]  K. Cammanna.  NIR-Remote Sensing and Artificial Neural Networks for Rapid Identification of Post Consumer Plastics , 2017 .

[21]  B. G. Achhammer,et al.  Infrared spectra of thermally degraded poly(vinyl-chloride) , 1958 .

[22]  Douglas N Rutledge,et al.  Rapid discrimination of plastic packaging materials using MIR spectroscopy coupled with independent components analysis (ICA). , 2014, Waste management.