A critical review on combining adsorption and photocatalysis in composite materials for pharmaceutical removal: Pros and cons, scalability, TRL, and sustainability

Abstract

Pharmaceuticals have been detected in water matrices with different concentrations raising the concerns about their effects on the environment and human health. Despite these concerns there are no clear regulations established by governments about the maximum accepted values of these pollutants in potable water. It is important that stake holders establish regulatory limits to the permitted concentration of pharmaceuticals in water bodies. Adsorption and photocatalysis are common techniques that have been studied to treat these pollutants. However, they each have challenges and limitations. As a result, combining both processes seem to be the way forward. Composite materials combining adsorption and photocatalysis tend to in most cases have an improved specific surface area, electron hole separation efficiency and electrical properties that are beneficial for their application in water treatment. In this work the advantages, disadvantages, sustainability, and cost implications of the methods used to synthesize these composites materials were discussed. To better outline their impact in combining adsorption and photocatalysis, the challenges and limitations of using a single technique were listed. The technology readiness level (TRL) of the techniques was also presented. Different types of composite materials have been studied, and their stability, regeneration and recyclability are still under development. It is evident how focus on pollutants has been expanded during the last decade, and year by year more research results on how to remove pharmaceuticals from water are reported. The synthesis, design and efficiency of the materials have improved through the years, however though still at the laboratory scale.