Nanoelectrocatalysts-Enhanced Methods for Removal of Volatile Organic Compounds in Wastewater

The degradation by biological processes of a large majority of organic volatile contaminants in wastewater is limited. This is so, largely because the reaction is inhibited at concentrations higher than 50 mg.L−1, thus, requiring costly physical or physiochemical pre-treatment(s). Electrochemistry currently plays an important role in a vast number of fundamental studies and applied areas in the treatment of pharmaceutical effluents. Pharmaceutical effluents are wastewater generated through various pharmaceutical processes such as the manufacturing of active pharmaceutical ingredients and product formulation. This wastewater is characterized by high concentrations of organic matter, catalysts such as TiO2/g-C3N4 and cathodic WO3/W nanocatalysts, and toxic pollutants that include Benzene, ethylbenzene, and Toluene). In recent times, electrochemical treatment has been attracting researchers as an emerging technology used for the removal of organic and inorganic impurities from water and wastewater. Many scientists are attempting to use these methods for the treatment of wastewater owing to the many advantages associated with electrochemistry compared to their biological or biotechnological counterparts. Although several review papers are available regarding the application of electrochemical methods for the environmental clean-up of pharmaceutical wastewater, research focussing on the development of efficient technologies coupled with the use of electrochemical and photocatalytic nanocatalysts continues. This chapter presents a detailed review of methods for the electrochemical degradation of volatile organic compounds in wastewater catalysed by nanocatalysts with an emphasis on pharmaceutical wastewater or effluents. An extensive review of the mechanism and application of these nanocatalysts-promoted electrochemical processes for degradation, mineralization, and detoxification of different organic pollutants present in industrial pharmaceutical wastewater will be reported. Electrochemical methods for the destruction of organic pollutants in wastewater is becoming very attractive in the industry because it is a powerful and promising clean method with undisputable environmental friendliness. Furthermore, the electrochemical treatment methods can be set up easily and show high efficiency. Analytical challenges encountered in the physical and electrochemical characterisation of some of these nanocatalysts will be briefly discussed. The reason for an accurate analytical characterisation is to check the composition, structure, dispersion on, and active surface area of the nanocatalysts, as well as the electrochemical systems. This guarantees the quality of the electrochemical data obtained. Finally, electrochemical and differential electrochemical mass spectrometry measurements used in specific cases to study and evaluate the influence of the electrocatalyst structure on its electroactivity will be discussed. This type of study allows for the investigation of the effect of the composition in terms of foreign metal atoms and atomic content of nano-metals-based catalysts (e.g. ZnO, TiO2, or CuO) towards the electro-oxidation of the organic pollutants. This chapter concludes by presenting the summary of the principles, advantages, and limitations, as well as the performances and some of the successful applications of the nanocatalysed electrochemical degradation of volatile organic compounds in wastewater using pharmaceutical effluents as an example.