Scavenging of nitrate ions from water using hybrid Al2O3/bio-TiO2 nanocomposite impregnated thermoplastic polyurethane nanofibrous membrane

Abstract

In the present study, we have exploited the nitrate adsorption property of Al₂O₃/bio-TiO₂ nanocomposite (ABN) and ABN impregnated electrospun thermoplastic polyurethane nanofibrous membrane (ABN/TPU-NFM) for water purification. Nitrate adsorption was investigated both in batch and dip mode studies. Parameters like effect of contact time, adsorbate concentration and membrane size were optimized. The adsorption capacity (Q_o) of the ABN and ABN/TPU-NFM was found to be 30.3 and 14.9 mg g⁻¹, respectively. Kinetics of the adsorption process was studied using pseudo-first-order and second-order models and it was found to obey pseudo-second-order kinetic model. The phase identification, crystalline stability and the surface functional groups of the adsorbents involved in nitrate adsorption were characterized using X-ray diffraction (XRD) and Fourier transform infra-red (FTIR) spectroscopy. Leachability studies carried out using atomic absorption spectroscopy (AAS) indicated that there was no leaching of impregnated nanoparticles from ABN/TPU-NFM in the treated water. No significant cytotoxicity for ABN was observed when tested with mouse fibroblast cells (L929), suggesting that the developed hybrid adsorbent is biocompatible and safe for drinking water purification. Further, field trial was carried out using natural ground water sample collected from nitrate contaminant area and tested for nitrate removal by dip mode adsorption process using ABN/TPU-NFM. The treated water was found to be potable having permissible limit of nitrate. This facile approach of designing nanocomposite impregnated nanofiber membrane is efficient in removing nitrate from contaminated drinking water.