| Title | Kinetic investigation on UV and UV/H2O2 degradations of pharmaceutical intermediates in aqueous solution |
| Abstract | The degradation kinetics of two pharmaceutical intermediates [5-methyl-1,3,4-thiadiazole-2-methylthio (MMTD-Me) and 5-methyl-1,3,4-thiadiazole-2-thiol (MMTD)] have been studied in order to assess the effectiveness and the feasibility of UV processes for the degradation water polluted by such intermediates. Experiments were carried out, at 25°C, treating, in a batch reactor, aqueous solutions (1 and 100 mg/L) of both compounds by UV radiations (254 nm) in the presence or absence of hydrogen peroxide. For both substrates, the results showed that: (i) no degradation occurred when H2O2 alone was used; (ii) UV and UV/H2O2 processes were both effective for degrading the substrates; (iii) substrates degradation by photo-oxidation was always faster than by direct photolysis; (iv) during direct photolysis, a lower substrate initial concentration lead to a faster and more efficient degradation. The quantum yields of the photolytic process were experimentally measured for both substrates resulting 14.1 1.5 and 12.0 0.7 mmol/einstein-1 for MMTD-Me and MMTD, respectively. Carrying out photo-oxidation experiments using excess of peroxide [i.e., initial substrate concentration of 1 mg/L and H2O2/substrate molar ratios of 50/1, 42/1, 34/1 and 23/1], first- and second-order rate constants for MMTD-Me and MMTD degradation were calculated. In particular, the values of these latter resulted (8.30.8)108 and (1.60.5)1010 M-1s-1, respectively. Our results show that to remove a few g/L of the pharmaceutical intermediates, a H2O2 dose of 1 mg/L, 99% would only need 55 min for (MMTD-Me) and 2.7 min (MMTD) |
| Source | Journal of photochemistry and photobiology. C, Photochemistry reviews (Print) 156, pp. 121–136 |
| Keywords | kineticspharmaceutical intermediatesUVUV/H2O2water treatment |
| Journal | Journal of photochemistry and photobiology. C, Photochemistry reviews (Print) |
| Editor | Elsevier Science, Amsterdam, Paesi Bassi |
| Year | 2003 |
| Type | Articolo in rivista |
| Authors | Lopez A.(1), Bozzi A.(2), Mascolo G. (3), Kiwi J.(4) |
| Text | 42068 2003 kinetics pharmaceutical intermediates UV UV/H2O2 water treatment Kinetic investigation on UV and UV/H2O2 degradations of pharmaceutical intermediates in aqueous solution Lopez A. 1 , Bozzi A. 2 , Mascolo G. 3 , Kiwi J. 4 1,2,3 CNR Ist. di ricerca sulle Acque. 4 Swiss Federal Institute of Technology Lausanne, Switzerland. The degradation kinetics of two pharmaceutical intermediates 5 methyl 1,3,4 thiadiazole 2 methylthio MMTD Me and 5 methyl 1,3,4 thiadiazole 2 thiol MMTD have been studied in order to assess the effectiveness and the feasibility of UV processes for the degradation water polluted by such intermediates. Experiments were carried out, at 25°C, treating, in a batch reactor, aqueous solutions 1 and 100 mg/L of both compounds by UV radiations 254 nm in the presence or absence of hydrogen peroxide. For both substrates, the results showed that i no degradation occurred when H2O2 alone was used; ii UV and UV/H2O2 processes were both effective for degrading the substrates; iii substrates degradation by photo oxidation was always faster than by direct photolysis; iv during direct photolysis, a lower substrate initial concentration lead to a faster and more efficient degradation. The quantum yields of the photolytic process were experimentally measured for both substrates resulting 14.1 1.5 and 12.0 0.7 mmol/einstein 1 for MMTD Me and MMTD, respectively. Carrying out photo oxidation experiments using excess of peroxide i.e., initial substrate concentration of 1 mg/L and H2O2/substrate molar ratios of 50/1, 42/1, 34/1 and 23/1 , first and second order rate constants for MMTD Me and MMTD degradation were calculated. In particular, the values of these latter resulted 8.30.8 108 and 1.60.5 1010 M 1s 1, respectively. Our results show that to remove a few g/L of the pharmaceutical intermediates, a H2O2 dose of 1 mg/L, 99% would only need 55 min for MMTD Me and 2.7 min MMTD 156 Lopez A., Bozzi A., Mascolo G., Kiwi J. Journal of Photochemistry and Photobiology A Chemistry, 2003, 156 1 3 pp. 121 126. 2003_J_Photoch_Photobiol_A_Chem.pdf Articolo in rivista Elsevier Science 1389 5567 Journal of photochemistry and photobiology. C, Photochemistry reviews Print Journal of photochemistry and photobiology. C, Photochemistry reviews Print Journal of photochemistry and photobiology. Print antonio.lopez LOPEZ ANTONIO giuseppe.mascolo MASCOLO GIUSEPPE |
