Efficient destruction of humic acid with a self-purification process in an Fe0-FeyCz/Fex-GZIF-8-rGO aqueous suspension

Natural organic matter (NOM) has diverse negative impacts on water purification, however, preventing them occurrence very difficult. Herein, humic acid (10 mg/L), as the main component of NOM, is completely destructed within 120 min in the Fe-0-FeyCz/Fe-x-GZIF-8-rGO air-saturated aqueous suspension without additional energy input, while its mineralization is followed by three kinetic constants within 480 min. During the process, HA was first complexed with Fe-0-FeyCz/Fe-x-GZIF-8-rGO by pi-pi interaction and H-bonding interaction and cleaved to aromatic compounds and then to alkanes and alcohols with some small acids before 120 min. The electron paramagnetic resonance (EPR) analysis and density functional theory (DFT) calculations confirmed that a strongly polarized alkane-alcohol complex was formed after 150 min with an electron-rich hydroxyl group area in alcohol and an electron-poor alkane area. Moreover, the more electrons of alkane in the complex are delocalized and trapped by O-2, with the adsorption of the alkane-alcohol complex on the catalyst surface based on the analyses of both electrochemical impedance spectroscopy (EIS) and chronoamperometry, greatly promoting the surface cleavage and hydrolytic process of alkane in the complex and producing more center dot OH for pollutant degradation than it does from the HA surface complex, which results in the highest mineralization rate in the period of 150-390 min. Our findings demonstrated that the current system is very promising for complex mixture-containing water purification without additional energy.

Automated summary

This study demonstrates that the Fe-0-FeyCz/Fe-x-GZIF-8-rGO catalyst can effectively remove organic matter from water. By forming complexes with humic acid, more hydroxyl radicals (OH) are generated for pollutant degradation, resulting in a higher mineralization rate.