Soil decontamination by natural minerals: a comparison study of chalcopyrite and pyrite

Environmental context With the rapid pace of industrialisation and urbanisation, soil contamination by organic pollutants has become a global focus of concern due to its serious threat to ecosystems and human health. Although a myriad of synthetic catalysts have been developed, natural minerals have the potential to be developed into cost-effective, environmentally benign and efficient catalysts to decontaminate soil. The efficient performance of natural minerals demonstrated in this study indicates a potential for their utilisation in the removal of refractory organic pollutants in soil. Rationale Organic pollution of soil has raised worldwide concern owing to the potential effects on ecosystems and human health. Natural metal minerals rich in transition metal elements have the potential to be developed into environmentally benign activators of peroxymonosulfate (PMS) and hydrogen peroxide (H2O2) for soil decontamination. Methodology A comparison study employing natural chalcopyrite (NCP) and natural pyrite (NP) as activators in the combined Fenton-like systems of PMS and H2O2 to degrade organic pollutants in soil has been carried out. Tetracycline hydrochloride (TCH) and phenanthrene (PHE) were selected as representatives of widely existing contaminants, antibiotics and polycyclic aromatic hydrocarbons, in the study. Key parameters including initial pH, catalyst and oxidants dosage were also optimised. Results A total organic carbon (TOC) removal efficiency of 68.66% was achieved for TCH (500 mg kg–1) with the addition of 0.75 g L–1 NCP, 1.23 mM PMS and 1.23 mM H2O2 within 4 h, whereas a slightly lower mineralisation efficiency of 64.78% was obtained by the NP heterogeneous system. For PHE (50 mg kg–1), 93.04% of TOC was removed using a NCP/PMS/H2O2 process, which was much higher than that of NP (45.76%) after 24 h. The quenching experiments indicated that ˙OH prevailed over SO4˙−EN22116_IE1.gif, and ˙O2−EN22116_IE2.gif also played a vital role in the PMS/H2O2 coupling process. Discussion The more superior performance of NCP has been elucidated via X-ray photoelectron spectroscoy analysis and comparison of catalytic mechanisms. The existence of Cu+ played an important role in the transformation of Fe3+ to Fe2+ and facilitated the continuous generation of active radicals. A possible degradation pathway was proposed based on the intermediates identified by GC-MS analysis. We anticipate this study would provide implications for the utilisation of natural minerals in the removal of refractory organic pollutants in soil.