Removal of estrone in water and wastewater by photocatalysis: A systematic review

Introduction. Estrone (E1) is a type of natural hormone estrogen which is produced mainly by the ovaries, adipose tissue, fibroblasts skin, placenta, and brain. E1 is part of the so called endocrine disrupting compounds (EDC), a type of organic contaminants present at trace levels in the water that can interfere with the normal function of the endocrine systems in humans and wildlife. Objective. To describe the experimental conditions that have given the best results in the degradation or photocatalytic removal of estrone referenced in the scientific literature using photocatalysis. Materials and methods used a systematic review, directed by search criteria, inclusion and exclusion, to extract information concerning the experimental conditions. Results. The results show that a) a higher removal rate is achieved with a higher load of the catalyst or with a modified catalyst; b) the use of radiation at 254 nm is convenient in matrices containing mixtures of compounds; c) the ideal pH will be lower than the isoelectric point or the zero charge point of the catalyst; d) the removal rate is faster in ultra-pure water than in synthetic or real wastewater. The study was limited to the identification of investigations in which the degradation was performed using TiO₂ as a catalyst and the articles fulfilled the inclusion and exclusion criteria. Conclusions. The main contribution of this research is the identification of the best conditions for the degradation of the pollutant in different conditions and matrices, which is the basis for the work of the research group. The removal of estrone is greater when the catalyst load is increased or by the use of a modified one; or when the pH is lower than the isoelectric point or the zero charge point of the catalyst; higher in ultra-pure water than in wastewater.