Photocatalytic decomposition of Cu-EDTA complex by macroporous and bimodal porous titania

Abstract

Ethylenediaminetetraacetic acid (EDTA), a strong chelating agent, is widely used in applications such as metal plating, water softening, photography, textile and paper manufacture, and industrial cleaning of the power generating station. EDTA forms very stable chelates with almost all metals (1:1) that causes water contamination. To remove this heavy metal along with chelating compound such as Cu-EDTA, macroporous titania and bimodal porous titania photocatalysts were prepared by spray pyrolysis. XRD (X-ray Diffraction), SEM (Scanning Electron Microscopy), TEM (Transmission Electron Microscopy), $N_2$ adsorption/desorption method, and mercury porosimeter were used to characterize the prepared titania photocatalysts. Photoactivity of titania photocatalysts was determined by measuring the decomposition rate of Cu-EDTA and fraction of removed copper. The concentration of metal-EDTA was measured by HPLC (high performance liquid chromatography). The concentration of copper in the solution was measured by AA (atomic absorption spectrophotometer). Polystyrene(PS) latex particles of various submicrometer size were used as templates to prepare macroporous titania. PS latex changed surface area of the photocatalyst by forming macroporous titania and changing macropore size. PS latex particles of 220 nm and 50 nm in diameter were used as templates in the optimum mixing ratio of 15:1 and 20:1 to prepare porous titania with bimodal pore size distribution. Mixed PS latex of 220 nm and 50 nm in diameter changed pore morphology of the photocatalyst from macropore only to the mixed pores of macropore and mesopore. In this study, the photoactivity of macroporous titania was much higher than that of nonporous titania because of the increased surface area. The photoactivity was increased linearly with the decrease of PS latex size up to 170 nm because the surface area was increased linearly with the decrease of PS latex size. When the size of PS latex diminished to 130 nm, photo...