Cost of adsorbent preparation and usage in wastewater treatment: A review

•The cost of adsorbent preparation and usage was reviewed (2016 – 2022).•A quantitative metric the adsorbent cost performance, Ĉ (in $/mol) was developed.•Adsorbents at 〈 1 $/mol are relatively cheap while those 〉 200 $/mol are expensive.•Cost analysis can extend the practical relevance of routine adsorption studies .