Enhanced nitrates-polluted water remediation by polyurethane/sepiolite cellular nanocomposites

Abstract

Nanocomposite hydrophilic flexible polyurethane foams were prepared by in situ polymerization using an organomodified sepiolite as filler. The sepiolite affinity by nitrates dissolved in water was increased by treating them with quaternary ammonium salts (S-QAS), leading to remarkable nitrates maximum adsorption capacity (qmax = 23.30 mg/g). The Langmuir model well described the adsorption process of the nitrates by the modified sepiolite, and more remarkably, the sepiolite suffers no decrease of their nitrates removal capacity after being imbibed in the flexible polyurethane foam. The proper selection of the polyurethane chemistry allows significant contact between the polluted-water and the sepiolite, even when enclosed inside the cell walls. Accordingly, the as-prepared hydrophilic polyurethane/sepiolite foams provided a facile removal of nitrates-pollution from water, even actual nitrates-polluted water with a competitive adsorption environment, without the need to control or modify the pH and temperature of the polluted water neither to add further filtration steps to collect the active particles from the water.