Purify

v.capable, hopefulprofessional

What it means

To remove harmful or unwanted material so something becomes clean or safe.

Reach for it when describing a process that eliminates contaminants from a substance

Layers of sand and charcoal purify the collected rainwater.

everyday
sanitize
for reducing microorganisms to an accepted hygiene level
not when Sanitize does not mean removing every impurity or all microbes.
warm
cleanse
when unwanted material is washed or cleared away
not when Cleanse can sound ceremonial or wellness-oriented and may not guarantee purity.
professional
decontaminate
when dangerous biological, chemical, or radioactive matter is removed
not when Decontaminate addresses safety and can leave harmless impurities behind.
professional
filter
if contaminants are physically separated by a barrier or medium
not when Filtering removes selected particles but may leave dissolved hazards.
professional
sterilize
if all viable microorganisms must be destroyed or removed
not when Sterilize is a narrower and much stronger microbiological claim.
formal
refine
when processing removes rough components to improve material quality
not when Refining may prioritize performance or taste rather than safety.
literary
clarify
when suspended matter is removed from a liquid to make it clear
not when Clarify concerns appearance and does not establish that the liquid is safe.

purify water
The portable unit can purify water for thirty people each day.
purify the air
Dense plantings helped purify the air beside the school entrance.
purify a substance
The chemist repeated the wash to purify a substance needed for testing.

The definition and the example on this page are written here. The dictionaries above ground which meaning is being described, not the wording.