This review provides a descriptive analysis of metformin, highlighting its environmental presence and classification as an emerging contaminant. It examines the risks associated with metformin and evaluates advanced oxidation processes (AOPs) for its degradation, including photolysis, photocatalysis, electrolysis, and ozonation. Metformin, a widely used biguanide for type 2 diabetes, is increasingly detected in aquatic environments due to its incomplete metabolism in humans, raising ecological concerns. While certain AOPs, such as ultraviolet (UV) photocatalysis and ozonation, achieve high degradation rates of 99.9% and 100%, respectively, they produce toxic by-products harmful to aquatic systems. Solar photocatalysis, despite a lower degradation rate (74.22%), stands out for operating without artificial energy and generating fewer hazardous by-products. The review identifies gaps in current degradation strategies and underscores the need for clean, sustainable methods. Future research directions include advancing biological and photocatalytic technologies to improve AOPs’ efficiency while minimizing environmental risks.

Access to drinking water is a human right recognized by the United Nations. It is estimated that more than 2.1 billion people lack access to drinking water with an adequate microbiological quality, which is associated to 80% of all diseases, as well as with millions of deaths caused by infections, especially in children. Water disinfection technologies need a continuous improvement approach to meet the growing demand caused by population growth and climate change. Heterogeneous photocatalysis with semiconductors, which is an advanced oxidation process, has been proposed as a sustainable technology for water disinfection, as it does not need addition of any chemical substance and it can make use of solar light. Nevertheless, the technology has not been deployed industrially and commercially yet, mainly because of the lack of efficient reactor designs to treat large volumes of water, as most research focus on lab-scale experimentation. Additionally, very few applications are often tested employing actual sunlight. The present work provide a perspective on the operation trends and advances of solar heterogeneous photocatalytic reactors for water disinfection by systematically analyzing pertaining literature that made actual use of sunlight, with only 60 reports found out of the initially 1044 papers detected. These reports were discussed in terms of reactor employed, photocatalyst used, microorganism type, overall disinfection efficiency, and location. General prospects for the progression of the technology are provided as well.

Phenol is a recalcitrant anthropogenic compound whose presence has been reported in both wastewater and drinking water; human exposure to phenolic substances can lead to health problems. The degradation of phenol (measured as COD decrease) through solar heterogeneous photocatalysis with immobilized TiO₂ was performed in two different reactors: a flat-plate reactor (FPR) and a compound parabolic collector (CPC). A 2³ full factorial experimental design was followed. The variables were the presence of TiO₂, H₂O₂ addition, and the type of reactor. Data were fitted to the pseudo-first-order reaction-rate-kinetics model. The rate constant for photocatalytic phenol degradation with 1 mM of H₂O₂ was 6.6 × 10⁻³ min⁻¹ for the FPR and 5.9 × 10⁻³ min⁻¹ in the CPC. The calculated figures of merit were analyzed with a MANCOVA, with UV fluence as a covariate. An ANCOVA showed that the type of reactor, H₂O₂ addition, or fluence had no statistically significant effect on the results, but there was for the presence of TiO₂. According to the MANCOVA, fluence and TiO₂ presence were significant (p < 0.05). The CPC was on average 17.4% more efficient than the FPR when it came to collector area per order (A_CO) by heterogeneous photocatalysis and 1 mM H₂O₂ addition.