Comparative study on nano-crystalline titanium dioxide catalyzed photocatalytic degradation of aromatic carboxylic acids in aqueous medium

A study on deactivation and regeneration of titanium dioxide during photocatalytic degradation of phthalic acid

“…The adsorption of carboxylic acids over negatively charged TiO 2 surface can be considered as electrostatic interaction of carboxylate ion with protonated titanol (>Ti-OH 2 + ), formed by reaction of titanol (>Ti-OH) with H + ions of carboxylic acid. The phthalic acid and the intermediate acids (like intermediate A, B and C) formed during PCD (Scheme 1) undergo PCD by surface adsorption followed by electron transfer [16]. The carboxylic acid intermediates formed during TiO 2 catalyzed reactions have been reported to be strongly adsorbed on the surface active sites [14,15].…”

“…The PCD of phthalic acid was carried out in aqueous medium as reported in our previous work [16]. The aqueous solution of phthalic acid (250 ml; 100 ppm) was taken in a photocatalytic batch reactor equipped with a magnetic stirrer and water cooling jacket from outside the reactor.…”

“…The aqueous phase photocatalysis in water helps to remove reaction intermediates and products from the catalyst surface, whereas, in gas phase these species try to accumulate on the surface causing the deactivation of the catalyst. In our previous study on TiO 2 catalyzed PCD of substituted aromatic carboxylic acids (benzoic acid, phthalic acid, o-chloro benzoic acid and o-nitro benzoic acid) in aqueous medium, TiO 2 was found to be an active photocatalyst for removal of highly stable carboxylic acid compounds [16]. However, it was observed that the spent TiO 2 catalyst had lesser catalytic activity for PCD of phthalic acids in next cycles than fresh TiO 2 catalyst showing deactivation of the catalyst.…”

“…The studies on deactivation and regeneration of TiO 2 for PCD in liquid phase reactions are scanty and it needs to be studied in detail for practical application of this technique. Therefore, in continuation of our previous work on TiO 2 catalyzed PCD of phthalic acid [16], the present study was aimed to investigate the cause of deactivation of TiO 2 catalyst during PCD of one of the aromatic carboxylic acid; phthalic acid as a model organic pollutant. The major regeneration methods used in gas phase catalysis reported in the literature include thermal treatment in presence of air [17,18], H 2 O 2 treatment in presence as well as in absence of UV light [13], sonication in water and methanol [19], irradiation of UV light in flow of humid air [8], etc.…”

Quantum chemical modeling study of adsorption of benzoic acid on anatase TiO2 nanoparticles

“…The present work is focused on investigating the adsorption of aromatic molecules on the anatase TiO 2 surface, for which benzoic acid (BZA) has been selected as a model compound, in part due to its environmental impact as a common recalcitrant contaminant [11]. We have carried out computational modeling in order to simulate different modes of adsorption of BZA onto the anatase TiO 2 surface, and to probe the electronic properties and stability of the various modes of adsorption.…”