INFLUENCE OF SOME AROMATIC AND ALIPHATIC-COMPOUNDS ON THE RATE OF PHOTODEGRADATION OF PHENOL IN AQUEOUS SUSPENSIONS OF TIO2

The influence of 3-nitrophenol, 4-nitrophenol, pentachlorophenol, etha nol, 2-propanol, ethanoic acid and ethanedioic acid on the photodegrad ation rate of phenol in an aqueous suspension of TiO2 (anatase) irradi ated in the near-UV region was investigated. Binary mixtures of organi c compound and phenol in molar ratios of 1:1 and 10:1 were used for th e photoreactivity experiments performed in a batch reactor. The minera lization rate of all the mixtures was also monitored by measuring the total organic carbon (TOC) concentration. The reactivity results indic ate that the photodegradation rate of phenol is mainly determined by t he total amount of aromatic substrates present in the reacting medium independently of their nature, while it is scarcely affected by the pr esence of aliphatic compounds. The TOC results indicate that the miner alization rate of aromatic compound-phenol mixtures is sensitive to th e mixture composition, and the simultaneous presence of phenol and ali phatic compounds negatively affects the mineralization rate. A tentati ve explanation of the above behaviour is proposed by taking into accou nt (i) the similar manner of photoadsorption of phenol molecules and o f the other aromatic compounds on the active surface site(s), (ii) the different sites of photoadsorption for aromatic and aliphatic substra tes and (iii) the possible formation of stable intermediate compounds from the degradation products of phenol and aliphatic compounds.