engleski

Influence of the Pharmaceutical Adsorption on the Electrochemical Response of Photocatalysts

It is well known that adsorption of organic substances on metal oxides is relevant to water remediation through photocatalytic or photoelectrocatalytic processes due to the short life time of generated charge. The adsorption will provide oxidative degradation of organics by valence-bound holes or by radicals generated during a photocatalytic or photoelectrocatalytic process [1, 2]. Therefore, in order to estimate the efficiency of a photocatalytic or photoelectrocatalytic process it is important to determine the affinity of an organic pollutant for the adsorption. Preliminary investigations by electrochemical techniques can provide us with useful information related to the adsorption and redox reactions of the pollutants. The target pollutants investigated in this work were pharmaceuticals, while potential photocatalysts were TiO2, SnS2, TiO2/SnS2 and reduced graphene oxide/TiO2/SnS2. The investigations were carried out in a 0.1 mol dm-3 NaCl solution by using linear polarization, electrochemical impedance spectroscopy and by monitoring open circuit potential. Three different pharmaceuticals were tested (memantine hydrochloride, diclofenac and salicylic acid) and all the measurements were carried out by using UV or LED lamps as light sources. The obtained results indicate that the presence and type of the pharmaceutical will significantly influence the photoelectrochemical response of the catalyst. Some of the tested pharmaceuticals have exhibited hole scavenger properties that increased the photocurrent response while others decreased the photocurrents due to the adsorption lessening the photoactivity of the catalyst. Pharmaceutical adsorption also influenced the open circuit potential as well as the electrochemical impedance spectroscopy results. Therefore it was concluded that the adsorption process can be successfully monitored by fast and simple electrochemical techniques. Furthermore, by monitoring the photocatalyst response in the dark as well as light it is possible to distinguish the photocatalytic and electrochemical contribution to the oxidation of pharmaceuticals.

pharmaceuticals, adsorption, electrochemical, photocatalyst

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