Comparison of the efficiencies of pyrite and zero-valent iron activated peroxydisulfate systems to degrade methomyl in water

作者：Hayat, Waseem; Zhang, Yongqing^*; Liu, Ze-hua^*; Du, Xiaodong

来源：SEPARATION AND PURIFICATION TECHNOLOGY, 2023, 306: 122619.

DOI：10.1016/j.seppur.2022.122619

• Methomyl (MET)
• Pesticides pollution
• Peroxydisulfate (PDS) oxidation
• Water treatment
• Zero-valent iron (ZVI)

The high leachability and solubility of methomyl (MET; C5H10N2O2S) result in water pollution; while, the polluted water channels can be depolluted by environmentally-friendly and highly-effective degradation tech-nique. Therefore, MET degradation in water by peroxydisulfate (PDS) oxidation was investigated in this study employing the two most naturally-abundant iron species i.e. pyrite (PyR) and zero-valent iron (ZVI) as activators for PDS activation. The experiments were conducted at different activators' dosage, pollutant concentration, oxidant concentration, initial pH and initial temperature for comparative assessment of degradation-efficiencies of PyR/PDS and ZVI/PDS systems. Using 0.25 g/L PyR/ZVI and 1.0 mmol/L PDS, PyR/PDS and ZVI/PDS systems respectively led to 98.8 % and 97.5 % degradation of 20.0 mg/L MET in 20 min, which became rapid by increasing the activators' dosage and oxidant concentration in both systems. Further, the degradation has been more than 90.0 % at initial pH 3.0 to 11.0, which slowed with increasing the MET concentration in two systems. The free-radicals quenching analysis showed that degradation by PyR/PDS system was mainly executed by sulfate (SO4 center dot-) and hydroxyl ((OH)-O-center dot) radicals; while, SO4 center dot- and super oxide radical anion (O-2(center dot-)) were dominant during degradation by ZVI/PDS system. PyR/PDS system had low stability and applicability, which supports the employment of ZVI/PDS system for efficient degradation of MET in water.