I think I know what Trump was talking about
Methylene Blue is an injectable compound that was once widely used as a disinfectant. Now is used for Cancer Treatments, Malaria and maybe now SARS-CoV-2.
It's what Chloroquine comes from.
A cohort of cancer patients with no reported cases of SARS-CoV-2 infection: the possible preventive role of Methylene Blue
https://riviste.fupress.net/index.php/subs/article/view/888
They already use Methylene Blue and Light to clean up Blood Products.
Methylene blue photochemical treatment as a reliable SARS-CoV-2 plasma virus inactivation method for blood safety and convalescent plasma therapy for the COVID-19 outbreak
https://www.researchsquare.com/article/rs-17718/v1