Efficient removal of petroleum hydrocarbons from soil by percarbonate with catechin-promoted Fe(III)/Fe(II) redox cycling: Activation of ferrous and roles of ·OH and ·CO3-

Abstract

Advanced oxidation processes are widely used to remove petroleum hydrocarbons from soil, but usually consume large quantities of ferrous and acidify the soil. This study tested an advanced oxidation approach based on percarbonate in laboratory experiments. It removed 88% petroleum hydrocarbons in soil with a pH increase from 8.2 to 10.2. ·OH and ·CO3- were the main reactive species, and degraded 41% and 37% PHCs from soil respectively. The o-dihydroxybenzene structure in catechin was found to reduce ferric to ferrous, and prolong the generation of ·OH from 120 s to over 1800 s. The petroleum hydrocarbons were degraded to intermediates including alkanes and olefins through hydrogen-abstraction by ·OH and ·CO3-, and by dimerization and β-scission of alkyl radicals. These intermediates were then oxidized to CO2 and H2O by ·OH and ·CO3-. The main residual intermediates in the soil were low-molecular-weight n-alkanes and branched alkanes, and they were found to inhibit the growth of oats (Avena sativa L.) much less than the original petroleum hydrocarbons. These findings provide a fundamental basis for designing effective technologies which use percarbonate to remove organic pollutants.