Photocatalytic materials and light-driven continuous processes to remove emerging pharmaceutical pollutants from water and selectively close the carbon cycle

Pharmaceutical pollutants are increasingly being present in water effluents. Over the past decades, the emergence of advanced oxidation processes has provided a tool to catalytically remove organic pollutants and harmful pathogens. However, researchers have focused too often on increasing the degradation rate of the contaminants, without ensuring as well the formation of more biodegradable products. As a result, by-products that are more toxic than the initial substrate have frequently been formed, limiting the industrial and societal exploitation of this technology. In an attempt to urgently fill this gap, this minireview analyses in a holistic manner past and present technologies for water purification, outlining possible examples of ultraselective photocatalytic materials and reactor concepts to obtain biodegradable products. Based on the analysis conducted, guidelines for the rational design of catalytic materials and for the selection of emerging reactor concepts are put forward. We also highlight current technological barriers and future research needs that should be explored in greater depth in the quest for integrated and intensified continuous-flow operations. Past and present technologies for wastewater purification and future research directions are critically discussed in this review.