Quantifying cellulose content in plastic-cellulose material mixtures

This study investigates the capabilities of various measurement techniques for quantifying the cellulose content in reject material from a carton recycling center, which consists of polyethylene, cellulose, and aluminum, along with impurities. Different measurement techniques, including Fourier Transform Infrared Spectroscopy combined with Attenuated Total Reflectance (FTIR-ATR), cellulose dissolution using cupri-ethylenediamine (CED) from plastic followed by gravimetric analysis, acid hydrolysis combined with chromatography, and Thermal Gravimetric Analysis TGA, are employed in this study. Acid hydrolysis combined with chromatography and TGA shows comparable results when compared to different techniques for analyzing pulper reject. Dissolution with CED showed also comparable results but shows higher variation than TGA or chromatography. FTIR absorbance ratio of 1025/2917 correlates with cellulose content, but it shows high variation and lacks sensitivity below 5% cellulose content in polyethylene. This limitation is attributed to factors such as the limited measurement area (1.8 mm) and the large particle size of the cellulose and LDPE mixtures, possibly caused by inadequate grinding of LDPE. In conclusion, TGA and acid hydrolysis combined with chromatography are the most reliable for quantifying cellulose content in recycling reject, providing more consistent and accurate results than FTIR-ATR or CED dissolution methods.