Insight into utilisation of ilex pur-purea waste extract as an eco-friendly promoter in Fe activated persulfate oxidation for remediation of organic contaminated soil

Abstract

Extensive research has been conducted with regard to in situ remediation of organic contaminated soil by Fe2+-activated sulphate radical-based advanced oxidation processes (SR-AOPs). However, rapid Fe2+ exhaustion and a narrow applicable pH has inhibited the development of this technology. In this study, we propose a strategy for introducing extra excess ilex pur-purea leaves from garden pruning into the persulfate (PS)/Fe2+ system to promote the degradation of organic contaminants in soil. The results demonstrated that adding small quantities of additional ilex in the Fe2+/PS system could exert a long-term influence on Fe3+/Fe2+ circulation and promote the degradation of naphthalene (NAP), whereby the removal efficiency increases from 38.59% to 71.78% over 180 min. Meanwhile, owing to the excellent simultaneous chelating and reducing abilities of the ilex extra under pH = 2–9, we obtained a performance superior to the conventional chelating agent (ethylene diamine tetraacetic acid) and reducing agent (ascorbic acid). Investigation of the mechanism revealed that protocatechuic acid and its byproducts (semiquinone and benzoquinone) were the main reactive components in the added ilex extra, by which adequate SO4−· and ·OH were generated for NAP degradation. Furthermore, in situ field remediation potential was supported in contaminated real soil, by the efficacy of NAP degradation in soil characterized by diverse environmental factors. More importantly, at least 60 times the dosage of PS and iron reagents were saved, which greatly reduced the cost of remediation and secondary pollution risks. This study not only revealed the effect of ilex addition on the acceleration of the degradation of organic contaminants by the Fe/SR-AOPs, but also shed new insight into the application of eco-friendly natural plant wastes for in-situ remediation of contaminated soil.