Remediation of soil contaminated with PAHs and γ-HCH using Fenton oxidation activated by carboxymethyl cellulose-modified iron oxide-biochar

The remediation of soil contaminated with hydrophobic organic pollutants has attracted great public concern. In the present study, a novel catalyst using biochar supported ferro ferric oxide modified by carboxymethyl cellulose (CMC-Fe3O4/BC) was developed to activate the Fenton reaction for hazardous hydrophobic organic pollutants, and the degradation mechanisms were analyzed in terms of free radicals, electron transfer pathways and degradation intermediates. The results showed that the CMC-Fe3O4/BC-activated H2O2 system degraded nearly 100% of pyrene in the aqueous system after a 1440-min reaction. The catalyst was also applied to remediate industrial field soil contaminated with PAHs and γ-HCH. The removal rate of the total pollutants reached 61.1% after a 10-day reaction, which was higher than that of Fe3O4/BC without modification. CMC enabled the Fe3O4 particles to more equably distribute on the BC surface, further effectively activating H2O2 to generate more ⋅OH and forming different degradation products compared to the Fe3O4/BC. Additionally, the CMC-Fe3O4/BC-activated H2O2 system obviously enhanced electron transfer on the BC surface. Thus, the PAHs and γ-HCH could be degraded via electron transfer pathways. [Display omitted] •CMC-Fe3O4/BC activated H2O2 effectively degraded PAHs and γ-HCH in field soil.•OH and electronic transfer played key roles in the field soil remediation.•CMC made Fe3O4 equably distributed on BC surface, benefiting to the remediation.•Two new degradation products were generated using CMC-Fe3O4/BC than Fe3O4/BC.•CMC played key role in the PAHs oxidation degradation.