Extraction of contaminants from HDPE wastes: is a rinse sufficient?

Abstract : The issue of plastic waste valorisation or recycling has become urgent lately. With China’s decision to recycle plastic wastes only if those are thoroughly cleaned and decontaminated, EU faces an impasse. Some European waste collectors use solvents or lye while grinding wastes to ensure decontamination. Nevertheless, that method has not be proven to be efficient enough. The goal of the following study is to evaluate the decontamination effects of a rinse and consequently assess if chemical migration into plastic takes place in the plastic jar lifetime. Present work dealt with real plastic waste provided by a waste collector. Consequently, it a blend of chipped jerry cans that had contained several chemicals. In order to evaluate the solvent rinsing decontamination capacity, an Accelerated Solvent Extraction (ASE) was performed (110 bars for 120°C) on plastic wastes ground to 1 mm particles (HDPE- 1mm). As a results, 21 molecules were extracted, quantified an identified with GC-MS analysis. A comparison with clean HDPE showed that this method did not extract organic additives at required levels to be detected. The quantification of minerals was not performed. Same not grounded plastic wastes (HDPE-2cm) were also rinse for 24h with several solvents: either pure acetone, acetonitrile, dichloromethane or mixtures of acetone / acetonitrile, acetone / dichloromethane and acetonitrile / dichloromethane at different proportions (9:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:9). Using GC-MS analysis, the contaminants in the rinse solutions were identified and quantified to be compared with the analysis performed after ASE. Firstly, as expected, 24h rinsing process performance was lower than ASE. Best observed extraction performance was 57% of ASE. Besides, not every molecules were extracted with a simple rinse, this method is not selective and thorough enough. Secondly, some mixtures were more efficient than pure solvents: acetone/acetonitrile 1:1. As a result, those contaminated plastics cannot be cleaned thoroughly by rinsing. They must be excluded from recycling in favour of valorisation.
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Esteban Helias, Francisco Javier Escudero Sanz, Didier Grouset. Extraction of contaminants from HDPE wastes: is a rinse sufficient?. WASTEENG 18 - 7th International Conference on Engineering for Waste and Biomass Valorisation, Jul 2018, Prague, Czech Republic. p.899-906. ⟨hal-01890489⟩

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