Photocatalytic degradation of methylene blue using nanoporous carbon-supported Fe composites, effect of P concentration.

Abstract

Carbon-supported PO4 3-/Fe3+-based nanocomposites were prepared by a thermal hydrolysis method. Fe concentration was constant ca. 1 wt. % while different molar ratios PO4 3-/Fe3+ were varied from 0-1.5. The influence of the molar ratio upon the kinetics of adsorption and photocatalytic activity in the degradation of methylene blue was evaluated. The photocatalytic tests were performed at ambient temperature in an open-to-air photoreactor and using a medium pressure Hg-lamp. The photoactivity of Fe-containing sample decreased in comparison to that of the commercial activated carbon F-400 in absence of phosphate, while a volcano-type behaviour was found with a maxima photoactivity up to 8 times higher than F-400 for the sample that contains a PO4 3-/Fe3+ equal to 0.5. A ternary photocatalyst was prepared using the best carbon-supported P-Fe-based material and a commercial TiO2 and the photocatalytic activity was measured showing a synergy effect between both solids up to a factor of 3 was verified. A mechanism for trimer aggregation of methylene blue adsorption with carbon-supported P-Fe-based nanocomposite is proposed to explain the decrease in surface density and photoactivity at high PO4 3-/Fe3+ molar ratio.