Most studies have reported that suspended photocatalysts are more efficient due to large surface area available for the reaction. The main drawback of using nano- or micro-particles in suspension is the requirement for post-treatment retrieval or recycling of the catalyst, potentially making the treatment more complex and expensive. Therefore, photocatalysis employing immobilized TiO₂ have gained more attention. Unfortunately, immobilizing TiO₂ on a solid substrate reduces the surface area available for reaction and limits the mass transfer of reactants to the photocatalyst surface in addition to making it more expensive. Besides, the question of the mechanical stability of the photocatalytic layer arises.

The capability of TiO₂ to inactivate a wide range of pathogens has been a successful field of research since 1985. E. coli has been the most frequently studied microorganism for water disinfection studies, as it is an indicator of faecal contamination and reference for water quality. Other bacteria (including spore-forming species) and fungi such as Bacillus pumilus, Serratia marcescens, Staphylococcus aureus, total coliforms, Pseudomonas aeruginosa, Salmonella typhimurium, Enterobacter cloacae, Saccharomyces cerevisiae, Candida albicans, and Fusarium solani were also inactivated using TiO₂ photocatalysis. In addition, plant pathogens were found to be inactivated in water using TiO₂-based catalysts like spores of Fusarium solani, Fusarium oxysporum, Fusarium verticillioides, Fusarium equiseti and Fusarium anthophilum. Other infectious agents such as viruses and prion proteins were also investigated, and some authors demonstrated the inactivation capacity of irradiated TiO₂ to degrade and inactivate them in water. Moreover, the capability of immobilized TiO₂ to inactivate oocysts of Cryptosporidium parvum was demonstrated under natural sunlight.

So far, the broad application of this technique has been mostly hampered by the lack of appropriate photocatalysts that combine efficiency and low cost with mechanical stability and easiness of recovery and reuse. But these problems are solved with ASDIS photocatalyst (patent granted at the Spanish Patent and Trademark Office in Madrid, with No. ES2916381 and issue date 13 April 2023, and pending at the Ecuador’s National Service of Intellectual Rights in Quito, Application No. SENADI-2021-16937 with priority date 10 March 2021), where the semiconductor is not just immobilized at the surface of the support material, but homogeneously mixed to form a cheap, bulky composite easy to filter out.