Role of operating parameters in photoelectrocatalytic degradation of anticancer drugs: Ifosfamide, 5-fluorouracil and imatinib using CdS/TiO2

Abstract

The ineffective removal of drugs in conventional wastewater treatment plants causes the search for new, effective and environmentally friendly methods. The promising alternatives consist photoelectrocatalysis. However, there is still lack of information about applied it for anticancer drugs removal and the influence of process conditions on its effectiveness. In the presented research CdS/TiO2 nanocomposite was applied in photoelectrocatalytic degradation of tree anticancer drugs: ifosfamide, 5-fluorouracil and imatinib. The effect of the process parameters such as applied potential, irradiation power, pH and conductivity of solution, drug concentration and presence of inorganic ions was investigated. It was shown that efficiency of drug degradation strongly increased with increasing irradiation power and with decreasing pH. The minor effect on the degradation efficiency of drug was observed with changing the potential and conductivity of the solution. In turn, presence of Cl−, NO3−, HCO3−, HPO42− in the treated solution acted as scavengers of hydroxyl radicals and decrease the decomposition rate. Studies on photoelectrocatalytic mechanism, shown that imatinib degradation occurs mainly as a result of holes activity, with slightly lower contribution of superoxide and hydroxyl radicals. On the other hand, 5-fluorouracil was degraded mainly by the holes and hydroxyl radicals, the superoxide radicals had a marginal participation. Based on a identified by-products, degradation pathways for 5-fluorouracil and imatinib have been proposed. Finally, research confirmed decreasing eco-toxicity towards duckweed (Lemna minor) of drugs solutions treated by photoelectrocatalysis.