Removal of bismerthiazol from water using zerovalent iron: Batch studies and mechanism interpretation

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Abstract Bismerthiazol [N,N′-methylene-bis(2-amino-5-mercapto-1,3,4-thiadiazole)] is one of the most widely used thiadiazole fungicides. While the bismerthiazol has great mobility in the subsurface environments (e.g., soil), the bismerthiazol and its derivative (i.e., thiadiazole) were shown to be toxic to organisms. The methods used for treatment of bismerthiazol, however, have not been presented to date. This study thus investigated the effectiveness of using microscale zerovalent iron to remove bismerthiazol from water. Batch experiments were performed to investigate the kinetics of removal of bismerthiazol by zerovalent iron at different bismerthiazol concentrations, iron dosages and solution pHs. Results show that the zerovalent iron is very effective to remove bismerthiazol from water. The removal can be described by pseudo-second-order kinetic model. X-ray diffraction and mass spectrometry examinations show that bismerthiazol was removed from water through complex with iron surfaces by forming Fe–S bond. The presence of NaCl in the solutions has minor influence on the remove of bismerthiazol whereas CaCl 2 can decrease the removal efficiency at high concentrations (e.g., 0.1 M). The presence of NaNO 3 has significant influence on the removal of bismerthiazol even at low concentrations (e.g., 0.01 M). Whereas pesticides are commonly removed by zerovalent iron thorough degradation, our results indicate that removal of bismerthiazol by zerovalent iron is due to surface complex. Our study shows that the zerovalent iron might be potentially useful for utilities to control fungicides in water and wastewater treatment.