Improvement of Solar Photo-Fenton by Extracts of Amazonian Fruits for the Degradation of Pharmaceuticals in Municipal Wastewater

Extracts of copoazu (Theobroma gramdiflorum), canangucha (Maurita Flexuosa), and coffee (coffea arabica) were explored as enhancers of the solar photo-Fenton process to eliminate acetaminophen, sulfamethoxazole, carbamazepine, and diclofenac. The process performance, at pH 6.2 and 5 mg L− 1 of iron without the extracts, has a very limited action (~ 35% of the pollutants degradation at 90 min of treatment) due to the iron precipitation. Interestingly, the extracts addition increased the soluble iron forms but only copoazu extract improved the pollutants degradation (~ 95% of elimination at 90 min of the process action). The copoazu extract acted as a natural complexing agent, maintaining the soluble iron up to 2 mg L− 1 even after 90 min, and consequently enhancing the pollutants degradation. The effect of copoazu extract dose on the process performance was also assessed, finding that an iron: copoazu extract molar ratio equal to 1:0.16 was the most favorable condition. Then, the process improved by copoazu extract was applied to municipal wastewater. Remarkably, the process led to ~ 90% of total pharmaceuticals degradation at 20 min of treatment. This work evidences the feasibility of amazonian fruits extracts to improve the solar photo-Fenton process to degrade pharmaceuticals in aqueous matrices at near-neutral pH.

Pharmaceuticals degradation by UV and UV/H2O2 treatments

The degradation by UV and UV/H2O2 treatments of the pharmaceutical intermediate 5-methyl-1,3,4-thiadiazole-2-methylthiol (MMTD-Me) has been investigated and compared to that of its parent compound [5-methyl-1,3,4-thiadiazole-2-thiol (MMTD)] previously studied. The investigation has been carried out with a 17 W low pressure mercury lamp, at room temperature, with an initial MMTD-Me concentration of 1 mg/l and with a molar ratio H2O2/substrate of 100/1. The results show that: (i) the complete MMTD-Me removal is achieved within 60 and 20 minutes by UV and UV/H2O2 treatment respectively; (ii) the UV only irradiation does not cause any MMTD-Me mineralization; (iii) the UV/H2O2 treatment, after 4 hours, leads to a complete mineralization of MMTD-Me organic sulfur and to a partial mineralization of carbon and nitrogen (79 and 16% respectively). Degradation by-products identification, performed by HPLC-UV-MS, revealed that the UV only irradiation gives rise to the sequential transformation of MMTD-Me into two by-products one of which, the last one, accumulates in the solution. Conversely, the UV/H2O2 treatment leads to the formation of two intermediate by-products that undergo further degradation with the breakdown of the thiadiazole ring. These results confirm the effectiveness of UV based processes, alone or in combination with H2O2, in degrading pharmaceutical intermediates.