Amicarbazone degradation promoted by ZVI-activated persulfate: study of relevant variables for practical application

Alarming amounts of organic pollutants are being detected in waterbodies due to their ineffective removal by conventional treatment techniques, which warn of the urgent need of developing new technologies for their remediation. In this context, advanced oxidation processes (AOPs), especially those based on Fenton reactions, have proved to be suitable alternatives, due to their efficacy of removing persistent organic compounds. However, the use of ferrous iron in these processes has several operational constraints; to avoid this, an alternative iron source was here investigated: zero-valent-iron (ZVI). A Fenton-like process based on the activation of a recently explored oxidant-persulfate (PS)-with ZVI was applied to degrade an emerging contaminant: Amicarbazone (AMZ). The influence of ZVI size and source, PS/ZVI ratio, pH, UVA radiation, dissolved O₂, and inorganic ions was evaluated in terms of AMZ removal efficiency. So far, this is the first time these parameters are simultaneously investigated, in the same study, to evaluate a ZVI-activated PS process. The radical mechanism was also explored and two radical scavengers were used to determine the identity of major active species taking part in the degradation of AMZ. The degradation efficiency was found to be strongly affected by the ZVI dosage, while positively affected by the PS concentration. The PS/ZVI system enabled AMZ degradation in a wide range of pH, although with a lower efficiency under slightly alkaline conditions. Dissolved O₂ revealed to play an important role in reaction kinetics as well as the presence of inorganic ions. UVA radiation seems to improve the degradation kinetics only in the presence of extra O₂ content. Radicals quenching experiments indicated that both sulfate (SO₄^•-) and hydroxyl (^•OH) radicals contributed to the overall oxidation performance, but SO₄^•- was the dominant oxidative species.