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

The cost of adsorbent preparation and usage is an important factor that determines its suitability for use in wastewater treatment in light of other competing technologies. Adsorbent cost can be determined via the cost of raw materials, discounted cash flow, cost indices, cost of adsorbent per gram of the adsorbate removed, Annual Capital Expenditure (CAPEX) and Operating Expenditures (OPEX), and the cost of adsorbent application in an adsorption operation. The need to unify the various concepts of adsorbent cost of different researchers and the evaluation of how the process efficiency affects the process cost prompted the need for this study. This paper aimed to review the cost of using different adsorbents for treating wastewater. It also developed a quantitative metric for comparing adsorbent costs known as the “adsorbent cost performance,” termed as Ĉ (and computed in $/mol). This was elucidated as the dollar cost of producing and using 1 g of an adsorbent for the removal of 1 mole of a chemical species in the aqueous phase, considered at the theoretical point of maximum uptake of the chemical species. There is a wide variation in adsorbent cost performance, but most adsorbents fall between 1 and 200 $/mol. Adsorbents at < 1 $/mol threshold can be considered very cheap for the intended application, while those at > 200 $/mol can be considered very expensive. More investigations into adsorbent cost analysis are encouraged, especially in routine adsorption studies, to help extend the practical relevance of these papers.