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

Abstract

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.

Graphical abstract