Covalent organic framework-coated alumina for the removal of geosmin from water in recirculating aquaculture systems

Geosmin, a prevalent taste and odor contaminant, can be perceived at extremely low concentrations, and its presence negatively impacts the commercial value of fish in recirculating aquaculture systems (RAS). Conventional water treatment processes have proven inefficient at removing geosmin, creating a need for alternative treatment solutions. To this end, adsorption is a promising method due to its simplicity and the reusability potential of adsorbents. Herein, we report the design, fabrication, and testing of a new adsorbent material based on a covalent organic framework (COF) immobilized onto alumina pellets for the removal of geosmin from RAS water. First, the selected β-ketoenamine-based COF was studied as adsorbent for geosmin. To allow for easier application of the material, the COF was then supported on alumina pellets as a homogeneous layer suitable for the application. After confirming the adsorption efficiency of the COF pellets for geosmin, they were tested in RAS water, both as a standalone removal method and in conjunction with ozonation in a treatment train. The COF pellets achieved 38% removal of geosmin from RAS water artificially spiked with realistic geosmin concentrations of 500 ng/L, and up to 70% when combined with ozonation. These results highlight the potential of COF pellets to be used as an effective method for geosmin removal, alone or as part of combined treatment with ozonation. • COF for the first time described to adsorb geosmin efficiently from water. • TpBD-Me2 COF can be efficiently regenerated and recycled with hexane. • Novel composite of TpBD-Me2 COF grown on polyethyleneimine-functionalized alumina pellets. • COF pellets adsorb geosmin from water up to 3.80 ± 0.22 mg of geosmin/g of COF. • Ozonation followed by adsorption by COF pellets removes 70% of geosmin from RAS waters.