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.

For further information, specifically on the use of desinfecting products please check the official publication (in Spanish) here.

In addition, you can also find the outline of three different masks available and how to use and re-use them in this article published by the El Pais newspaper (in Spanish).