MIL-88A（Fe） adsorption-photocatalytic synergistic degradation of phenanthrene-pyrene composite pollutants in soil

Polycyclic aromatic hydrocarbons （PAHs）， as a typical class of persistent organic pollutants （POPs）， are widely present in soils and pose a serious threat to ecosystems and human health. In this study， MIL-88A（Fe） catalyst was prepared using a hydrothermal solvent method and applied to the photocatalytic process of phenanthrene-pyrene （PHE-PYR） composite contaminated soil to investigate the adsorption-photocatalytic synergistic effect of MIL-88A（Fe） catalyst. The results showed that the adsorption behavior of MIL-88A（Fe） catalyst on PHE-PYR composite pollutants was dominated by physical adsorption and surface monolayer adsorption， with the maximum adsorption amount reaching 97.25 mg/kg， and the stronger adsorption capacity increased the concentration of pollutants near the active sites on the catalyst surface， which accelerated the pollutants' photocatalytic degradation efficiency； The adsorption-photocatalytic degradation of PHE-PYR composite pollutants in soil reached 79.20% at 3% catalyst dosage， 40% soil water content， 60 min light time， initial pollutant concentration of 200 mg/kg， and initial soil acidity. To further explore the photocatalytic reaction mechanism， the photoelectrochemical characterization results showed that the MIL-88A（Fe） catalyst had a remarkable photoresponsive ability in the visible wavelength range， and the narrow forbidden band width （3.04 eV） and energy band structure were conducive to the effective separation of photogenerated electron-hole pairs， which facilitated the photocatalytic reaction； and the results of the quenching experiments showed that the superoxide radicals （·O2-） and holes （h+） were the main active substances in the photocatalytic reaction system， and PYR was converted to PHE by hydroxylation， oxidation and ring-opening reaction under the action of the active radicals， and then PHE was further decomposed by hydroxylation and oxidation reaction， and finally mineralized to generate CO2 and H2O， which realized the PHE-PYR composite pollutants in soil The composite pollutants of PHE-PYR in soil were efficiently degraded.