Photolysis and UV/H 2 O 2 of diclofenac, sulfamethoxazole, carbamazepine, and trimethoprim: Identification of their major degradation products by ESI–LC–MS and assessment of the toxicity of reaction mixtures

Abstract

The photolysis of diclofenac (DCF), sulfamethoxazole (SMX), carbamazepine (CBZ), and trimethoprim (TMP) was investigated using a low-pressure (LP) mercury ultraviolet (UV) lamp (254nm) and a combination of UV with hydrogen peroxide (H 2 O 2). For each experiment, 5mg/L of each pharmaceutical was prepared in pure water and individually degraded by either UV alone or UV/H 2 O 2. DCF and SMX were highly susceptible to UV treatment and completely degraded to below their LC-MS detection limit (1μg/L) after only 8min of UV irradiation. TMP and CBZ were more resistant to UV treatment, with only 58.2 and 25.2% degradation (after 1h UV exposure). The combination of H 2 O 2 addition (up to 0.2g/L) with UV significantly improved the removal rate of TMP and CBZ up to 91.2 and 99.7% of the initial concentration, respectively. A number of novel transformation compounds were identified as UV or UV/H 2 O 2 degradation products using LC-MS. The range and amount of these transformation compounds strongly depended on the applied treatment conditions. The toxicity of each pharmaceutical solution before and after treatment was also evaluated and all parent compounds were non-toxic at the tested concentration (i.e. 5mg/L). DCF, in particular, but also CBZ and SMX, showed an increase in solution toxicity after treatment with UV only, indicating the presence of photolytic degradation products that are more toxic than the parent compounds. Treatment with UV/H 2 O 2 reduced the toxicity of all solutions to below the detection limit of the assay.

Carbamazepine as a Possible Anthropogenic Marker in Water: Occurrences, Toxicological Effects, Regulations and Removal by Wastewater Treatment Technologies

“…For instance, adding a single dose of H 2 O 2 (5-15%) to UV photolysis process resulted in an enhanced CBZ removal of 60-75% [225,226]. In another study, H 2 O 2 -concentration dependent increase in CBZ removal by UV/H 2 O 2 process was reported, and 99% removal was achieved at an initial H 2 O 2 concentration of 120 mg/L [220]. CBZ removal can improve with increasing H 2 O 2 concentration but it will reach a plateau beyond a threshold H 2 O 2 concentration [220].…”

“…Although UV photlysis alone has been observed to be ineffective for CBZ removal (0-20%) in a number of studies [220,231], removal can be significantly improved by adding H 2 O 2 or a photocatalyst such as TiO 2 [214,220]. For instance, adding a single dose of H 2 O 2 (5-15%) to UV photolysis process resulted in an enhanced CBZ removal of 60-75% [225,226].…”

“…Moreover, transformation products formed following the oxidation of PhACs including CBZ can be more toxic than the parent compound [220]. To overcome this issue, the use of biological filters or ACs can be a suitable option [233,234].…”

Recent Advances in Water Management: Saving, Treatment and Reuse

“…Ternes et al [197] reported almost complete removal (>99%) of CBZ (35-1000 ng/L) during ozonation process at an initial dose of 0.5 mg/L. Although UV photlysis alone has been observed to be ineffective for CBZ removal (0-20%) in a number of studies [220,231], removal can be significantly improved by adding H 2 O 2 or a photocatalyst such as TiO 2 [214,220]. For instance, adding a single dose of H 2 O 2 (5-15%) to UV photolysis process resulted in an enhanced CBZ removal of 60-75% [225,226].…”

Impact of Hydrogen Peroxide on the UVC Photolysis of Diclofenac and Toxicity of the Phototransformation Products

“…The main goal of the present work was to compare the outcomes of UVC photolysis and UV/H 2 O 2 in the context of TPs analysis and toxicity assessment. As the previous efforts focused primarily on the photolysis process [12,13], the studies on the application of UV/H 2 O 2 towards diclofenac degradation are still rather scarce [1]. Therefore, there is a need for broad-scope experimental work aimed at providing a comparative perspective on the diclofenac-related outcomes of photolysis and UV/H 2 O 2 .…”