As the world faces water supply challenges, new water treatment technologies are increasingly drawing attention. One of the complexities water technologies pace is treating low concentration of emerging micro-pollutants, such as pharmaceuticals, in the presence of dissolved organic matter (DOM), a heterogeneous mixture of relatively large soluble organic compounds. We have demonstrated the efficient filtration of nonionic micro-organic pollutants by polymer-clay composite columns even in the presence of DOM. In the current study, new polymer-clay composites based on the adsorption of quaternized poly-4-vinylpyridine-co-styrene to montmorillonite were developed and optimized as sorbents for anionic micro-organic pollutants. Composite structure and stability were controlled by solution ionic strength; an increase in ionic strength induced polymer adsorption, increased surface charge and promoted a polymer loops and tails configuration. Composite structure was characterized by zeta potential, FTIR, X-ray diffraction and thermal gravimetric analyses. The affinity of the anionic pharmaceutical, diclofenac, to the composite was high and did not decrease dramatically with an increase of ionic strength, indicating that the interactions are not only electrostatic. Polymer adsorption in a loops and tails configuration, as opposed to a train one, promoted diclofenac removal. The adsorption kinetics of diclofenac to the composites was substantially faster than to granulated activated carbon (GAC). Equilibrium was reached within 10 minutes for the composites, whereas, for GAC it was reached only after 2-3 hours. Filtration of diclofenac in the presence of humic acid (a component of DOM) by the GAC columns was reduced, while the removal by the composite columns was not compromised and remained high. This important finding led us to investigate DOM removal by such composites. Indeed, DOM removal by the composites was high and attributed mainly to electrostatic interactions. A threshold in composite zeta potential was observed. Finally, DOM filtration with composite columns was significantly superior to filtration by GAC columns which may suggest that DOM and diclofenac adsorbed to different sites on the composite surface.

Developing polymer-clay composite sorbents for the removal of emerging organic pollutants from water

251st National Meeting (2016)

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