Insights into enhanced removal of fluoranthene by sulfidated nanoscale zero-valent iron: In aqueous solution and soil slurry

Activity and recyclability enhancement of pH-dependent Fe0@BC-mediated heterogeneous sodium percarbonate (SPC)-reducing agents (RA) system

Dyes pose great threats to the aquatic environment and human health. Fe0-based Fenton-like systems have been widely employed for the degradation of organic dyes. However, the regulation of degradability and recyclability was still unclear. In this study, Rhodamine B (RhB) was served as the model pollutant, hydroxylamine hydrochloride was selected as the RA, the natural photocatalysis system demonstrated stable operation. RA, as performance enhancement agent, was firstly reported in micro/nano-Zero-Valent Iron@Biochar (m/nZVI@BC) based SPC-RA system. Carrier size-fractionated m/nZVI@BC was fabricated by one-step carbothermal method. As a result, RA synergistically interacted with SPC, and the reaction time reduced from 15 min to 4 min. In the 0.010 g m/nZVI@BC-mediated SPC-RA system, over 95% of RhB (100 mg·L-1, 1041.667 mg·g-1) was successfully degraded. The maximum degradation ability could still exceed 1g·g-1 via 5 times repeated applications. Meanwhile, the loss of degradability, caused by halving SPC concentration could be compensated by RA dosage measurement. The entire degradation process was predominantly dominated by free radicals (•OH> 1O2> •O2-> •CO3-). Reactive oxidizing species (ROSs) were primarily excited by α-Fe0, Fe3C and N sites of biochar (BC). Light and BC carrier dedicated slight influence. These discoveries shed a light on the activity and recyclability regulation of catalytic material, aligning with the principles of green chemistry and cleaner production. This study demonstrates a novel approach to efficient management of solid waste disposal, reuse of waste biomass, advanced treatment of dye-containing wastewater, pollution control in aquatic environments.

Efficiency and mechanism on photocatalytic degradation of fluoranthene in soil by Z-scheme g-C3N4/α-Fe2O3 photocatalyst under simulated sunlight

Polycyclic aromatic hydrocarbons (PAHs) in soil have potential harm on human health. However, remediation of PAH-contaminated soils through photocatalytic technology remains a challenge. Therefore, the photocatalyst g-C₃N₄/α-Fe₂O₃ was synthesized and applied to photocatalytic degradation of fluoranthene in soil. The physicochemical properties of g-C₃N₄/α-Fe₂O₃ and various degradation parameters, such as catalyst dosage, the ratio of water/soil, and initial pH, were investigated in detail. In soil slurry reaction system (water/soil=10:1, w/w), the optimal degradation efficiency on fluoranthene was 88.7% after simulated sunlight irradiation for 12 h (contaminated soil=2 g, initial fluoranthene concentration=36 mg/kg, catalyst dosage=5%, and pH=6.8), and the photocatalytic degradation followed pseudo-first-order kinetics. The degradation efficiency of g-C₃N₄/α-Fe₂O₃ was higher compared with P25. Degradation mechanism analysis showed that •O₂^- and h⁺ are the main active species in photocatalytic degradation process of fluoranthene by g-C₃N₄/α-Fe₂O₃. Coupling g-C₃N₄ and α-Fe₂O₃ enhances the interfacial charge transport capacity via Z-scheme charge transfer route and inhibits the recombination of photogenerated electrons and holes of g-C₃N₄ and α-Fe₂O₃, then significantly improves the production of active species and photocatalytic activity. Results showed that photocatalytic treatment of soil by g-C₃N₄/α-Fe₂O₃ is an effective strategy for remediation of soils contaminated by PAHs.