Invited
Polymer-mineral composite sorbents: Effect of structure on pollutant removal from water

One of the complexities water technologies face, is treating low concentration of emerging micropollutants, such as pharmaceuticals, in the presence of higher concentrations of dissolved organic matter (DOM), a heterogeneous mixture of relatively larger soluble organic compounds. We develop polycation-clay composites based on the adsorption of poly-4-vinylpyridinuim to clay as sorbents for simultaneous removal of micropollutants and DOM. Polycation configuration at the adsorbed state, dominantly as trains (Comp-Train) and dominantly as loops and tails (Comp-L&T), was controlled by 1. solution ionic strength 2. polycation concentration 3. polycation charge density. Composite micro- and nano-structure was characterized by zeta potential, FTIR, X-ray diffraction and thermal gravimetric analyses. The removal of the micropollutants from tap water or from treated wastewater by the Comp-L&T was significantly higher than by the Comp-Train, even upon normalizing to the polymer loading. The removal by both composites was obviously higher from tap water (EC=0.75 dS/m) but the reduction in removal from treated wastewater (EC=1.5 dS/m) was not dramatic. Furthermore, this degree of reduction in micropollutant removal by the Comp-L&T was smaller than the degree of reduction by the Comp-Train. On the other hand, polymer configuration did not affect DOM removal. For the Comp-L&T we identified three diverse adsorption sites for the removal of anionic, cationic and nonionic micropollutants. These results support our hypothesis that a loops and tails configuration is beneficial for the removal of the small micropollutants, within the size range of polycation loops and tails.

Finally, the simultaneous filtration of micropollutants and DOM by composite columns was more efficient than by columns of commercial granulated activated carbon.