Organophosphorus pollutant degradation in wastewater using the microscale zero-valent iron/O3 process: optimization, performance, and mechanism

Tetrakis(hydroxymethyl)phosphonium sulfate (THPS) is commonly used as a preservative and fungicide in leather production that leads to its presence in tannery wastewater. As a typical organic phosphorus pollutant, THPS poses potential threats to both the ecological environment and human health. Herein, this investigation used the microscale zero-valent iron (mZVI)/O3 process to eliminate THPS from aquatic environments. The mZVI/O3 system demonstrated superior removal performance, achieving high removal efficiencies of total phosphorus (TP), organic phosphorus (OP), and chemical oxygen demand (COD) compared to traditional systems (i.e., mZVI alone, O3 alone, Fe2+/O3, and Fe3+/O3). Moreover, batch experiments were conducted to optimize the key operational parameters (such as initial pH, mZVI dosage, O3 concentration, and stirring rate). The TP, OP, and COD removal efficiencies in the mZVI/O3 system reached 97.10%, 97.31%, and 81.56% within 20 min, respectively, under optimized conditions. Based on the experimental results and characterization analysis, the THPS degradation mechanism by the mZVI/O3 system was primarily a combination of oxidation (60.37% ± 7.41%) and flocculation (39.63% ± 7.41%). Furthermore, the mZVI/O3 system demonstrated unprecedented removal performance in various actual wastewater samples. The system eliminated organic pollutants and improved biodegradability of actual wastewater. This study not only establishes the mZVI/O3 process as a robust, cost-effective, and environmentally sound approach for OP degradation but also offers substantial promise for practical wastewater treatment applications.