Magnetic semiconductor photocatalysts for the degradation of recalcitrant chemicals from flow back water

摘要

In the present study treatability of persistent organic compounds from the flow back water after hydrauling fracturing was investigated. The combination of TiO_2 photocatalyst and magnetic oxide nanoparticles enhance the separation and recoverable property of nanosized TiO_2 photocatalyst Fe_3O_4/ TiO_2 and Fe_3O_4©SiO_2/TiO_2 nanocomposites were prepared by heteroagglomeration. The photocatalysts' characteristics by X-ray diffractometry (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS) showed that sample with the mass ratio of Fe_3O_4 to TiO_2 equal 1:4 and molar ratio of TEOS:Fe_3O_4 = 8:1 and NH_4OH:TEOS = 16:1 obtained by deposition TiO_2 P25 (Evonik) on magnetite core had about 124 m~2 g~(-1) specific surface area and superparamagnetic properties. The prepared composites contained TiO_2 and Fe_3O_4 crystal phases. The photocatalytic activity was estimated by measuring the decomposition rate of three model pollutants identified in the flow back water from one of the Baltic Shale Basin. Regarding flow back water treatment after shale gas exploration, the progress of photo-catalytic degradation of organic compounds was measured by chemical oxygen demand (COD) concentration. The Fe_3O_4®SiO_2/TiO_2_P25 composite nanoparticles were recovered and re-used without significant reduction of efficiency.