Progress of Cryogenics and Isotopes Separation , ISSN: 1582-2575
2019, Volume 22, Issue 2
Pages 55-64

Reductive dechlorination of α-hexachlorocyclohexane by iron sulfide nanoparticles in batch experiments mimics its anaerobic biodegradation in environment - preliminary results

Abstract

Iron sulfide (FeS) is a reductive mineral naturally occurring in many anoxic environments. It is associated with sulfate-reducing bacteria that grow in anoxic aquifers and sediments. Many previously studies have reported the capacity of FeS for reductive dehalogenation of various halogenated organic pollutants. Therefore, a new method for FeS nanoparticles synthesis was developed in this study, to be used in reductive dechlorination of α-hexachlorocyclohexane (α-HCH), mimicking its transformation pathways in anoxic environments. To synthesize the FeS nanoparticles, a solution of 0.2M Na₂S was added over a solution of 0.2M FeSO₄, under a N₂ flow. The XRD analysis showed an almost amorphous phase of FeS nanoparticles, while the Raman and FTIR spectra were in accordance with the ones of FeS phases from the literature. The dehalogenation reaction was performed by mixing 1g of FeS nanoparticles with 100 mL N₂ flushed-water and by adding α-HCH from a stock solution in acetone to a final concentration in water of 9.80 mg/L. The dechlorination reaction was performed for 20 days in an incubator at 30°C and 125 rpm. For sampling, 14 mL aliquots of α-HCH solution were taken with syringes at determined intervals for gas chromatography-mass spectrometry (GC-MS) analysis. The degradation products identified by GC-MS were β-pentachlorocyclohexene, benzene and 1,2,4 trichlorbenzene, showing that the dehydrochlorination is the main degradation pathway of α-HCH by FeS. The experiment highlighted that the synthesized FeS nanoparticles degraded the α-HCH to an extent of about 53%, demonstrating their potential in dehalogenation of HCH isomers.

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