Removal of triphenyl phosphate by nanoscale zerovalent iron (nZVI) activated bisulfite: Performance, surface reaction mechanism and sulfate radical-mediated degradation pathway. (May 2020)

• Record Type: Journal Article
• Authors: Chen, Ruxia; Yin, Hua; Peng, Hui; Wei, Xipeng; Yu, Xiaolong; Xie, Danping; Lu, Guining; Dang, Zhi
• Is Part Of: Environmental pollution. Volume 260(2020)
• Publication Date: 2020-05
• Subjects: Triphenyl phosphate -- nZVI -- Bisulfite -- Surface reaction -- Sulfate radical (SO4−); Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2020.113983
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Recently, sulfate radical-based advanced oxidation processes (SR-AOPs) have been studied extensively for the removal of pollutants, however, few researches focused on the activation of bisulfite by nanoscale zerovalent iron (nZVI), especially, surface reaction mechanism and sulfate radical-mediated degradation pathway have not been elucidated in detail. In this study, influencing factors, the kinetics, transformation pathway and mechanism of triphenyl phosphate (TPHP) degradation in the nZVI/bisulfite system were systematically discussed. Compared with Fe 2+, nZVI was found to be a more efficient and long-lasting activator of bisulfite via gradual generation of iron ions. The optimal degradation efficiency of TPHP (98.2%) and pseudo-first-order kinetics rate constant ( k obs = 0.2784 min −1 ) were obtained by using 0.5 mM nZVI and 2.0 mM bisulfite at the initial pH 3.0. Both Cl − and NO3 − inhibited the degradation of TPHP and the inhibitory effect of Cl − was stronger than that of NO3 − due to the higher reaction rate of Cl − with SO4 − . Furthermore, SEM, XRD and XPS characterization revealed that a thin passivation layer (Fe2 O3, Fe3 O4, FeOOH) deposited on the surface of fresh nZVI and a few iron corrosion products generated and assembled on the surface of reacted nZVI. Radical quenching tests identified that SO4 − was the dominant reactive oxidative species (ROS) for TPHP removal. Based on HRMS analysis, six degradation products were determined and a sulfate radical-mediated degradation pathway was proposed. In a word, this study revealed that the nZVI/bisulfite system had a great potential for the TPHP elimination in waterbody. Graphical abstract: Image 1 Highlights: nZVI could permanently activate bisulfite so as to degrade TPHP efficiently. .SO4 − was a key free radical for TPHP degradation. The surface reaction mechanism of nZVI was emphatically elucidated. Six degradation products and an evolution pathway were proposed.