Dehalogenation of α-hexachlorocyclohexane by iron sulfide nanoparticles: Study of reaction mechanism with stable carbon isotopes and pH variations

International audienceThe biodegradation of hexachlorocyclohexanes (HCHs) is known to be accompanied by isotope fractionation of carbon (13C/12C), but no systematic studies were performed on abiotic degradation of HCH isomers by iron (II) minerals. In this study, we explored the carbon isotope fractionation of α-HCH during dechlorination by FeS nanoparticles at different pH values. The results of three different experiments showed that the apparent rate constants during dehalogenation of α-HCH by FeS increased with pH. The lowest apparent rate constant value α-HCH during dehalogenation by FeS was 0.009 d−1 at pH value of 2.4, while the highest was 1.098 d−1 at pH 11.8. α-HCH was completely dechlorinated by FeS only at pH values 9.9 and 11.8, while the corresponding apparent rate constants were 0.253 d−1 and 1.098 d−1, respectively. Regardless of the pH used, the 1,2,4-trichlorobenzene (1,2,4-TCB), 1,2-dichlorobenzene (1,2-DCB), and benzene were the dominant degradation products of α-HCH. An enrichment factor (εC) of −4.7 ± 1.3‰ was obtained for α-HCH using Rayleigh model, which is equivalent to an apparent kinetic isotope effect (AKIEC) value of 1.029 ± 0.008 for dehydrohalogenation, and of 1.014 ± 0.004 for dihaloelimination, respectively. The magnitude of isotope fractionation from this study suggests that abiotic isotope fractionation by FeS must be taken into account in anoxic sediments and aquifers contaminated with HCH isomers, when high concentrations of FeS are present in the above-mentioned anoxic environments

Corrigendum to “Dehalogenation of α-hexachlorocyclohexane by iron sulfide nanoparticles: Study of reaction mechanism with stable carbon isotopes and pH variations” [Sci. Total Environ., vol. 801, 20 December 2021, 149672]

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New Biodegradable Materials for Re-Thought Packaging from Pre-Consumer Wastes by Controlling the Storage Time as Method to Increase the Mechanical Recycling Efficiency

The influence of storage conditions on the mechanical recycling of pre-consumer waste (PRE-CW) from the manufacture of multilayer packaging films starting from starch compounds using a renewable-based polymer with PCL and PBAT, which are biodegradable conventional-based polyesters, was studied. It was found that, unlike materials based on conventional-origin polymers that accumulate in the environment for hundreds of years, the studied compounds degraded, even in the solid state, duringstorage in unventilated spaces and during the rainy hot summers with alternatingheat and rain. The degradation of the mechanically recycled compounds obtained from PRE-CW stored in such conditions was highlighted by the comparative analysis with the primary compounds, which proved the following: specific FTIR spectra changes; 2–3-times higher melt fluidity than for primary compounds; melting in successive processes over the entire positive temperatures range, up to 115 °C, such as in cases of compositional de-mixing of incompatible blends, faced to a single melting endotherm with a maximum at around 120 °C for the primar thermal degradation with the movement of the main destruction stages towards higher temperatures; a high quantity residue at 750 °C in air; dispersed mechanical resistance properties y compounds; crystallization at temperatures 10 °C–15 °C higher. The elimination of storage before the mechanical recycling of the pre-consumer waste from this type of polymeric compound fabrication is a way to increase the mechanical recycling efficiency while obtaining new materials with functional properties required by the applications