I think the most encompassing word for this topic is decontamination. It even covers some of the answers given so far.
[I'm surprised no one mentioned before. But yes, as OP mentioned contamination already, it seems like it might be less likely that he is looking for an obvious opposite. In the end, the term fits perfectly.]
Decontamination is the process of cleansing an object or substance to remove contaminants such as micro-organisms or hazardous materials, including chemicals, radioactive substances, and infectious diseases. Decontamination is sometimes abbreviated as "decon", "dcon" or "decontam".
The purpose of decontamination is to prevent the spread of micro-organisms and other contaminants that may threaten the health of human beings or animals or damage the environment.
Decontamination is most commonly used in medical environments, including dentistry, surgery and veterinary science, in the process of food preparation, in environmental science and in forensic science.
Methods of decontamination include:
- Physical cleaning
- Water purification
- Ultrasonic cleaning
(highlighted the keywords that you mentioned in the question)
Also, there is a term called clean technique for laboratory decontamination procedures.
Clean techniques refer to laboratory practices employed to reduce the risk of contamination. Clean techniques are employed in the forensic DNA laboratory to prevent the transfer of DNA from analyst to sample, environment to sample, and cross-contamination between samples. Contamination can adversely effect the outcome of a case; therefore, it is essential that the laboratory have procedures in place to limit, recognize, and address contamination.