UV and H2O2/UV degradation of a pharmaceutical intermediate in aqueous solution.
The degradation of 5-methyl-1,3,4-thiadiazole-2-thiol (MMTD), a pharmaceutical intermediate found in some aquifers of Northern Italy, has been investigated by means of UV and UV/H2O2 treatments. The study has been carried out with a 17 W low pressure mercury lamp at room temperature, using a (100)/(1) (H2O2)/(MMTD) molar ratio. The results have demonstrated that: (i) with an initial MMTD concentration of 1 mg/l, 90% MMTD removal can be achieved within 1 hour or less than 5 minutes by UV or UV/H2O2 respectively; (ii) the sole UV irradiation does not cause any MMTD mineralization; (iii) with an initial MMTD concentration of 50 mg/l, 4 hours of UV/H2O2 treatment lead to an almost complete mineralization of the MMTD organic sulfur and to a partial mineralization of carbon (59%) and nitrogen (14%). The identification of degradation by-products, performed by HPLC-UV-MS analysis, revealed that the sole UV irradiation gives rise to the MMTD transformation into a single by-product that continuously accumulates in the solution. Conversely, the UV/H2O2 treatment forms seven intermediates that undergo further degradation through the breakdown of the thiadiazole ring. On the basis of the obtained results a degradation pathway has been proposed.
Lopez
Antonio
A
Istituto di Ricerca Sulle Acque (IRSA), Consiglio Nazionale delle Ricerche (CNR) a, Via F. De Blasio 5, 70123 Bari, Italy. an.lopez@area.ba.cnr.it
Bozzi
Anna
A
Mascolo
Giuseppe
G
Ciannarella
Ruggiero
R
Passino
Roberto
R
D006861:Hydrogen Peroxide / Q000737:chemistry*; D016877:Oxidants / Q000737:chemistry*; D013830:Thiadiazoles / Q000737:chemistry*; D014466:Ultraviolet Rays; D014873:Water Pollutants; D018508:Water Purification / Q000379:methods*
D016877:Oxidants; D013830:Thiadiazoles; D014873:Water Pollutants; C049131:2-methyl-1,3,4-thiadiazole-5-thiol; D006861:Hydrogen Peroxide