The Health Ministry of Spain has recently published the following official guideline to desinfect and reuse of hygenic masks:

1. Wash and disinfect the masks with normal detergent and warm water with temperature between 60º-90º (normal washing machine cycle).
2. Soak the masks in a bleach dilluted with warm water with the proportion of 1:50 for 30 minutes. Then wash with soap and water and rinse well to remove any remaining bleach. Then let the masks dry.

In this article, you find the links to the official documents (in Spanish): https://www.clustercollaboration.eu/achievements/spain-guidelines-desinfection-and-reuse-hygienic-masks