Low-temperature catalytic aqueous phase oxidation of microcystin-LR with iron-doped TiO pillared clay catalysts.

TiO-PILCs and iron-doped TiO-PILCs were employed in order to destroy toxic microcystin-LR in the presence of HO under the UV light. While less than 5% of the initial microcystin-LR and TOC disappeared in 240 min with the TiO-PILCs, almost complete conversion of microcystin-LR could be achieved in 180 min on the 10 wt% iron-doped TiO-PILC-A. On the exterior surface of the iron-doped TiO-PILCs were mainly located iron particles which had nano-sized diameter and Fe/Fe cations together. Through Fenton-type oxidation on iron particles with HO, the big microcystin-LR molecules were converted primarily into smaller intermediate organic molecules of hydrocarbons, carboxylic acids and organic amines. The smaller intermediate molecules were believed to be diffused into the pores of the iron-doped TiO-PILCs and to be further mineralized into CO and HO through the action of photocatalysis on the TiO pillars. However, complete conversion of TOC could not be obtained due to the iron particle deactivation. XPS, TPO and TEM studies showed the continuous accumulation of carbonaceous materials onto the surface of iron particles.