Environmentally Friendly Catalysts for Energy and Water Treatment Applications

Dear Colleagues,

After the first successful Special Issue focused on energy and pollution control applications as catalysts, available here, we propose a second edition in the same line, now focused on water with regard to the environment, under the title: “Environmental Friendly Catalysts for Energy and Water Treatment Applications”.

Catalysts are extensively used in different technologies and play a fundamental role in the efficient generation of energy and industrial emission control. Despite the fact that catalysts have remarkable performance, they pose, in some cases, a negative environmental impact due to their massive use, which is imposed by intensive production strategies. Therefore, a reorientation in the search for new materials such as environmental friendly catalysts (EFCs) is urgently needed. Hence, the development of novel EFCs to face sustainable energy production, climate change problems, water resources conditioning and to abate industrial effluents has become a challenge in the current research fields.

A great variety of catalytic materials, which include single metals as well as mixed metals (and their oxides), are currently being used, either supported over alumina, silica, titania, ceria, zirconia, activated carbons, and zeolites or directly attached to the reactor itself, allowing their continuous use and avoiding waste emissions. Similar cases are found in Fenton catalysis, converted into EFCs through heterogeneous Fenton-like variants. Moreover, the combined use of catalysts with UV/solar irradiation or in combination with O₃ and H₂O₂ will always be preferable to that of other oxidant agents (persulfates). Heterogeneous catalysts are also used as electrodes for energy and environmental applications. Indeed, electrochemical processes are key technologies for sustainable development. This Special Issue addresses the aforementioned topics.

Prof. Dr. José Ignacio Lombraña
Dr. Hugo Olvera Vargas
Dr. Sandra Yazmin Arzate Salgado
Guest Editors

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• sustainable advanced oxidation processes (AOPs)
• green electrocatalytic processes
• sustainable catalytic processes
• water resources conditioning
• wastewater remediation
• green energy production
• environmentally friendly catalysts
• multiple reused catalysts

Title: Kinetic study of the water quality parameters during the oxidation of diclofenac by UV photocatalytic variants
Authors: N. Villota1* , B. Echevarria2, U. Duoandicoechea1, J.I. Lombraña3, A. De Luis2
Affiliation: 1 Universidad del País Vasco UPV/EHU, Dpto. de Ingeniería Química y del Medio Ambiente. Escuela de Ingeniería de Vitoria-Gasteiz. 2 Universidad del País Vasco UPV/EHU, Dpto. de Ingeniería Química y del Medio Ambiente. Escuela de Ingeniería de Bilbao. 3 Universidad del País Vasco UPV/EHU, Dpto. de Ingeniería Química. Facultad de Ciencia y Tecnología.
Abstract: Diclofenac, DCF (C14H11Cl2NO2) is a non-steroidal anti-inflammatory drug widely used, causing significant occurrence in waste effluents. DCF is especially persistent and difficult to degrade, with numerous toxic effects on aquatic fauna and humans. In 2015 DCF was included as priority pollutant (EU Directives on water policy). In this work, UV irradiation and their combination with hydrogen peroxide only or catalysed by iron salts (photo-Fenton) are analysed to find the most efficient alternative. DCF aqueous solutions were treated in a stirred 150 W UV photocatalytic reactor, with UV (300 and 570 nm), half-power, mercury lamps. According the case, 1 mM H2O2 and 0-5.0 mg/L Fe(II) catalyst, as FeSO4, was added. During reaction, DCF, pH, turbidity, UVA at 254 and 455 nm, dissolved oxygen (DO) and TOC were followed. The degradation of DCF yields a strong increase in the aromaticity because of the rise of aromatic intermediates, very stable and non-degradable by UV light. Thus, only if H2O2 is added, UV can completely degrade these aromatic colour intermediates. However, adding Fe2+ (photo-Fenton) the aromaticity remains constant due to iron complexes, that generates maximum colour and turbidity at an stoichiometric Fe(II):DCF ratio of 3. As a result of the study, it is concluded that, with UV light only, strong yellow colour is generated and maintained along the reaction, but adding H2O2, colourless appearance, low turbidity (<1 NTU) and [DO]=8.1 mg/L is obtained. Surprisingly, photo-Fenton was found inappropriate to degrade DCF.