I would add “sorption” as a Level 1 topic and put adsorption and absorption as subtopics.
unfortunately, there are only two levels available in the platform: “categories” and “subcategories” so we are in the CDR wiki category and the Unit Operations subcategory. Below that level, we cannot further sort the entries in tiers. But we can make the organization in text, and I will do that with brief edits to each of the entries: Sorption, Adsorption, Absorption, and Desorption.