Adsorption-based removal of pharmaceutical from water: A critical review on adsorbent performance

Pharmaceuticals and their persistent residues are usually found in the effluents of wastewater treatment plants (WWTPs). The European Commission, therefore, proposes that large WWTPs implement a quaternary treatment to remove such dissolved critical micropollutants before they are released into the environment. An additional adsorption stage downstream of the wastewater treatment plants could offer a potential solution. A large number of different adsorbents have been examined in the literature for their ability to adsorb dissolved pharmaceuticals. Most studies were undertaken at pollutant concentrations several orders of magnitude above those typically found in wastewater and focused on maximum adsorbate loadings as a performance criterion. This review draws on literature data regarding the adsorption performance of various pharmaceuticals by the most important adsorbent classes, including carbons, clays, silica, zeolites, and polymers. It demonstrates that the adsorption capacity alone is insufficient to describe an adsorbent’s efficiency in achieving the decontamination levels targeted by the EU. Instead, for typical European WWTP effluents with pharmaceutical contaminants in the lower ng to µg per liter range, both the adsorption capacity and the adsorption affinity of the adsorbent must be considered in order to determine the required adsorbent amount. Finally, DCF was considered as a case study in order to determine the quantities of adsorbents required for the removal of DCF in the low concentration range typical of wastewater.