**Preface to "Heterogeneous Catalysis and Advanced Oxidation Processes (AOP) for Environmental Protection (VOCs Oxidation, Air and Water Purification)"**

The quality of air and water is a key contemporary problem. The globalization economy and the current pandemic situation have given rise to new problems related to environmental protection. Catalysis science has always given smart, green, and scale-up eco-friendly solutions. In the last year, together with the traditional and efficient catalytic thermal treatments, new and emerging techniques such as photothermal treatments or advanced oxidation processes have provided good results both for air and water purification.

Based on the above considerations, this Special Issue on "Heterogeneous Catalysis and Advanced Oxidation Processes (AOP) for Environmental Protection (VOCs Oxidation, Air and Water Purification)"highlights the state of research on VOC oxidation (catalytic oxidation, photocatalytic oxidation or photothermal catalytic oxidation), air purification, and wastewater treatments (adsorption, membrane filtration, AOP, photocatalysis, Fenton and PhotoFenton, ozonation, etc.), as well as on the development of new catalysts for environmental protection.

From the high-quality papers presented in this book, researchers interested in these topics can find interesting and fascinating information, with contributions from some of the most important University and research centers in the world.

> **Roberto Fiorenza** *Editor*
