Key Takeaways & Executive Findings
- •• • MIL-88A(Fe) achieved a maximum adsorption capacity of 97.25 mg/kg for PHE-PYR, with adsorption dominated by physical monolayer surface processes, enhancing local pollutant concentration and subsequent photocatalytic efficiency. • • Under optimal conditions (3% catalyst dosage, 40% soil moisture, 60 min visible light, 200 mg/kg initial pollutant, acidic soil), the synergistic adsorption-photocatalytic degradation reached 79.20%, demonstrating practical viability for soil remediation. • • The catalyst exhibited a narrow bandgap of 3.04 eV and strong visible-light response (200–600 nm), enabling effective photogenerated electron-hole separation, critical for photocatalytic activity. • • Quenching experiments confirmed superoxide radicals (·O2−) and holes (h+) as dominant reactive species; GC-MS identified PYR conversion to PHE via hydroxylation/oxidation as a key degradation pathway, leading to complete mineralization.
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants ubiquitously present in soils, posing severe risks to ecosystems and human health. This study synthesized MIL-88A(Fe) via a hydrothermal solvent method and applied it to the photocatalytic degradation of phenanthrene-pyrene (PHE-PYR) composite contaminants in soil, investigating the adsorption-photocatalytic synergy. Results demonstrated that adsorption of PHE-PYR onto MIL-88A(Fe) was dominated by physical and monolayer surface adsorption, with a maximum adsorption capacity of 97.25 mg/kg. This strong adsorption increased pollutant concentration near active sites, accelerating photocatalytic degradation. Under optimal conditions—3% catalyst dosage, 40% soil water content, 60 min visible light irradiation, initial pollutant concentration of 200 mg/kg, and acidic soil—the total degradation efficiency reached 79.20%. Photoelectrochemical characterization revealed significant visible-light response (200–600 nm), a narrow bandgap of 3.04 eV, and favorable band structure facilitating efficient electron-hole separation. Quenching experiments identified superoxide radicals (·O2−) and holes (h+) as primary reactive species. GC-MS analysis of intermediates indicated that PYR undergoes hydroxylation, oxidation, and ring-opening to form PHE, which is further hydroxylated and oxidized, ultimately mineralizing to CO2 and H2O. This work provides an efficient strategy for remediating PAH-contaminated soils.
1. Introduction
Polycyclic aromatic hydrocarbons (PAHs) such as phenanthrene and pyrene are persistent organic pollutants that accumulate in soils due to industrial activities, posing long-term ecological and health risks. Conventional remediation methods, including physical removal and biological treatment, often suffer from slow kinetics, incomplete degradation, or high energy demands. Photocatalysis offers a promising alternative, but its efficiency is frequently limited by poor light utilization and rapid electron-hole recombination. The development of efficient, visible-light-active photocatalysts remains a critical bottleneck for practical soil remediation.
Metal-organic frameworks (MOFs), particularly iron-based MIL-88A(Fe), have emerged as attractive candidates due to their high surface area, tunable porosity, and photocatalytic activity. This study addresses the bottleneck by integrating adsorption and photocatalysis in a single material, enhancing pollutant concentration near active sites and facilitating degradation. The experimental protocol demonstrates a synergistic effect, achieving 79.20% degradation of PHE-PYR under optimized conditions, offering a scalable and energy-efficient approach for PAH-contaminated soil cleanup.
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ZHANG Chengxue, ZHANG Shuai, ZHAO Saisai, WANG Xiaocong, XIA Meng (2026). MIL-88A(Fe) Adsorption-Photocatalytic Synergistic Degradation of Phenanthrene-Pyrene Composite Pollutants in Soil. Journal of Environmental Engineering Technology. https://doi.org/10.13205/j.hjgc.202604026
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Frequently Asked Questions
What is the maximum adsorption capacity of MIL-88A(Fe) for PHE-PYR and what type of adsorption is it?
The maximum adsorption capacity is 97.25 mg/kg, and the adsorption is dominated by physical adsorption and monolayer surface adsorption, as indicated by the study.
What are the optimal conditions for achieving the highest degradation efficiency of PHE-PYR in soil?
The optimal conditions are 3% catalyst dosage, 40% soil water content, 60 minutes of visible light irradiation, initial pollutant concentration of 200 mg/kg, and acidic soil, yielding a total degradation efficiency of 79.20%.
What is the bandgap of MIL-88A(Fe) and how does it influence photocatalytic activity?
The bandgap is 3.04 eV, which is narrow enough to absorb visible light (200–600 nm) and facilitates effective separation of photogenerated electron-hole pairs, enhancing photocatalytic performance.
Which reactive species are primarily responsible for the degradation of PHE-PYR?
Quenching experiments identified superoxide radicals (·O2−) and holes (h+) as the main reactive species driving the degradation process.
What is the proposed degradation pathway of PHE-PYR?
GC-MS analysis suggests that PYR is first converted to PHE via hydroxylation, oxidation, and ring-opening reactions. PHE then undergoes further hydroxylation and oxidation, ultimately mineralizing to CO2 and H2O.
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