Enhanced gemfibrozil removal from treated wastewater by designed “loopy” clay-polycation sorbents: Effect of diclofenac and effluent organic matter

Novel clay-polymer nano composites (CPN) were designed for the removal of gemfibrozil (GFZ) from treated wastewater (TWW). The pyridine groups of poly-4-vinylpyridine (PVP) were 100% or 50% (randomly) substituted with bromo-ethanol to synthesize OH100PVP and OH50PVP, respectively. The effect of polymer charge density and loading on the structures of the CPNs, were investigated. At high polymer loadings OH100PVP adsorbed mainly in a flat configuration, as trains, while OH50PVP adsorbed in a more extended configuration, as loops and tails. The affinity and capacity of GFZ towards the OH50PVP CPN was significantly higher than to the OH100PVP, despite the latter's higher charge density, this high affinity of GFZ was explained in terms of more accessible adsorption sites due to the extended configuration of OH50PVP. The kinetics of GFZ removal from TWW by the CPN and by granulated activated carbon (GAC) was measured and modeled by the time dependent Langmuir equation. The effect of effluent organic matter (EfOM) and of a competing anionic pharmaceutical, diclofenac (DCF), on the kinetics of GFZ removal was thoroughly explored. Finally, the overall removal of the studied anionic pharmaceuticals was four-fold higher than by GAC at realistic contact times.