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

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 (k obs ) 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 (SiW 12 4− ) was obtained, which improved the transfer rate performance of electrons for activating PS; 2) singlet oxygen ( 1 O 2 ) 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.