Mechanochemically synthesized silicotungsten acidified ZVI composite for persulfate activation: Enhancement of the electron transfer and Fe slowly release mechanism.

ABSTRACT

Zero-valent iron (ZVI) is a promising technology for groundwater treatment, and its efficiency primarily depends on the electron transfer. However, there are still some problems such as low electron efficiency of ZVI particles and high yield of iron sludge that limits the performance, which warrant further investigation. In our study, a silicotungsten acidified ZVI composite (m-WZVI) was synthesized by ball milling to activate PS to degrade phenol. m-WZVI has a better performance on phenol degradation (with a removal rate of 91.82%) than ball mill ZVI(m-ZVI) with persulfate (PS) (with a removal rate of 59.37%). Compared with m-ZVI, the first-order kinetic constant (kobs) of m-WZVI/PS is 2-3 times higher than that of the others. Iron ion was gradually leached in m-WZVI/PS system, being only 2.11 mg/L after 30 min, having to avoid excessive consumption of active substances. The underlying mechanisms of m-WZVI for PS activation mainly include 1) were elucidated through different characterizations analyses that accounted for silictungstic acid (STA) can be combined with ZVI, and a new electron donor (SiW124-) was obtained, which improved the transfer rate performance of electrons for activating PS; 2) singlet oxygen (1O2) is the main active substance for phenol degradation, but other radicals also played an important role. Therefore, m-WZVI has good prospects for improving the electron utilization of ZVI.