Removal of drugs in aqueous systems by photoassisted degradation

Abstract

Aqueous solutions of tetracycline, lincomycin and ranitidine were irradiated with UV light in homogeneous and heterogeneous systems. Two commercial polycrystalline TiO 2 powders (Degussa P25 and Merck) were used as photocatalysts. After 5 h, an appreciable photolytic degradation of tetracycline and ranitidine was observed while the degradation of lincomycin was noticeably lower. As far as the mineralization is concerned, a small decrease of the TOC values was measured in the case of tetracycline whereas negligible variations were found for lincomycin or ranitidine. The presence of the photocatalysts greatly enhanced the degradation rates of the drugs with respect to those observed during the homogeneous experiments. The Langmuir-Hinshelwood kinetic model adequately describes the experimental results and both the pseudo-first order kinetic constants of the reactions and the adsorption constants were calculated. Merck TiO 2 was more active than P25 Degussa for the photodegradation of tetracycline and ranitidine, whereas both photocatalysts showed similar performances for lincomycin. In the presence of TiO 2 Degussa P25, tetracycline was almost completely mineralized, but the reduction of the initial TOC was ca. 60% in the case of lincomycin and ranitidine. A less significant mineralization was observed by using Merck TiO 2 .

Photocatalytic degradation of tetracycline using nanosized titanium dioxide in aqueous solution

“…Some researchers studied the application of UV/TiO 2 for degradation of TC antibiotics and concluded that this process was very efficient. Addamo et al (2005), who studied the application of this process for TC removal from aqueous solution, reported that TC removal efficiency above 98 % was obtained after 120 min with 100 % removal of total organic carbon. Reyes et al (2006), who studied TC photodegradation, reported 100 % of TC degradation after 120 min with higher mineralization level (90 %).…”

“…Photodeamination occurs after the TC exposure to UV irradiation. The removal of volatile dimethylamine needs the loss of only 2 carbon atoms according to the 22 atoms of tetracycline (Addamo et al 2005). Addamo et al (2005) reported 4a,12a-anhydro-4-oxo-4-dedimethylaminotetracycline as a major degradation product of TC photolysis by UV, whereas Jeong et al (2010) proposed products resulting from the loss of -NH 2 from the 2-carboxamide group and demethylation from the dimethylamine group at C-4, followed by loss of -OH at C-3.…”

Degradation of Aqueous Pharmaceuticals by Ozonation and Advanced Oxidation Processes: A Review

“…A very high second-order rate constant for the hydroxyl radical reactions was reported for the protonated form of ranitidine (pK a = 8.2; Figure 28 In addition, about 60% of TOC was removed by prolonged treatment for 5 h. On the other hand, direct photolysis was much less effective in ranitidine conversion and mineralization (Addamo et al, 2005). Hydroxylation of furan ring and S-oxidation were suggested as possible degradation pathways, although they were not experimentally demonstrated.…”

“…C, and about 60% of initial TOC was removed from the solution. Although S-oxidation of methylthio group and oxidation of pyrrolidine ring followed by a cleavage of amide bond were suggested as possible routes of lincomycin degradation by TiO 2 process (Addamo et al, 2005), the actual degradation intermediates and by-products were not determined, with the exception of sulfate ion.…”

Treatment options for wastewater effluents from pharmaceutical companies

“…Investigations into the removal of the pharmaceuticals using TiO 2 , include but are not limited to work on antibiotics, lipid regulators, x-ray contrast media, antiepileptics and antiphlogistics (Doll and Frimmel, 2005a, b and c;Perez-Estrada et al, 2005a). Removal rates have been reported at 98 % for antibiotics when used in combination with UV (Addamo et al, 2005). However, removal rates for carbamazepine are under 10 % (Doll and Frimmel, 2005a).…”