Increases in phosphate loads into freshwater rivers and lakes from agriculture and urban sources can make them prone to eutrophication. Prefiltration using the catch basin insert filters can be a viable solution to remove the excess phosphates entering the freshwaters. Catch basin insert filters have layers of filter media material that can remove the pollutant of interest using the adsorption process. Previous studies have shown FeO2 and MnO2 coated sorbents are effective for phosphate removal. In this study, we have coated polypropylene fabric with MnO2 and performed batch experiments to investigate its usage as a phosphate filter media that can be added into catch basin inserts. Results showed that the phosphate removal efficiency for MnO2 coated fabric was better than commercially available adsorbent filter media. Kinetic studies showed that the sorbent followed pseudo-second-order kinetics and Freundlich isotherm model fits revealed that the cooperative adsorption process is dominant. Thermodynamic calculation confirmed that phosphate adsorption onto MnO2 coated filter media is spontaneous. We have also developed other low-cost phosphate adsorbents from waste materials such as iron oxide coated walnut shells and pistachio nutshells to investigate a cost-effective sorbent where production can be scaled up to clean large amounts of agricultural and urban runoff.

Novel low-cost adsorbents for phosphate removal from freshwaters

ACS Fall 2021

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