This is a good read too and should be included probably somewhere here on the forum. Simply for the fact that members here are perhaps more likely to deal with soluble platinum than BeO.
https://ipa-news.com/assets/sustainability/IPA_Guidance/Chapter 6_PGM_Guide.pdf
https://ipa-news.com/assets/sustainability/IPA_Guidance/Chapter 6_PGM_Guide.pdf