Multilayer Active Nanostructures of Metal Oxide Semiconductors-Assisted Photooxidation of Wastewater for Voltammetric Determination of Heavy Metals

Abstract

The presence of organic matter (e.g. surfactants) is the most crucial problem in many analytical methods, such as inductively coupled plasma mass spectrometry (ICP MS), graphite furnace atomic absorption spectrometry (GF AAS) or electrochemical methods (stripping voltammetry). Voltammetry is a sensitive method of metal determination, only one an alternative to ICP MS. Only one limitation of the method is an influence of the organic matrix on the measurements. After the wet digestion with H2O2 accelerated with UV irradiation the evaporation of an excess of reagent is required. We present the application of “sunlight” assisted digestion in the presence of bare WO3 or multilayer metal oxide semiconductors (e.g. WO3 and Fe2O3) to the decomposition of dissolved organic matter, using the anionic surfactant sodium dodecyl sulfate (SDS) and the nonionic surfactant (1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (Triton™X-114) in natural water samples, prior to the determination of traces residues of lead by stripping voltammetry methods. The results of the study showed firstly that the preparation of reproducible WO3 layers characterized by high mechanical and chemical resistance was possible, and secondly that it was also possible to obtain a high efficiency of decomposition, equal in efficiency to that of the reference method, which was the hydrogen peroxide oxidation assisted by UV, with evaporation nearly to dryness. The developed procedure is suggested to be a no-reagents method for the decomposition of added SDS, leading to 100 % recovery of added Pb (II). Physicochemical properties (structure, morphology and spectroscopic identity) of the resulting hybrid (composite) WO3 films were assessed using X-ray diffraction, scanning electron microscopy, as well as UV-Vis and Raman spectroscopies. The electrochemical method (anodic stripping voltammetric - ASV) will be applied in practical study of the determination of various trace metals in natural water samples. For comparison, GFAAS and ICP-MS measurements would be performed as reference methods confirming the correctness of electrochemical measurements due to their different tolerance to the presence of the organic matrix in the samples.