Development of sustainable magnetic polyurethane polymer nanocomposite for abatement of tetracycline antibiotics aqueous pollution: Response surface methodology and adsorption dynamics

Poor surface characteristics and mechanical strength have impeded the industrial utilization of starch-based polymers for wastewater treatment. Though miniaturization of adsorbent materials to nano-scale level, has improved the surface area of materials, nano-scale adsorbents often form stable colloidal suspension/emulsion, and thus pose separation challenges. This study was designed to develop a novel starch-based magnetic polyurethane polymer for removal of tetracycline antibiotics from water media. Magnetic starch was synthesized by in-situ co-precipitation of Fe2+ and Fe3+ in the presence of starch, and thereafter subjected to one-step reticulation with 4,4-methylene diphenyl diisocyanate to produce magnetic starch polyurethane polymer nanocomposite (MSPP). The characterization studies with FTIR, SEM, TEM, XRD, VSM, BET, and XRF indicated successful synthesis. The characterization, adsorption isotherm and pH studies indicated π-π and π-cation interaction as possible adsorption interactions. Besides optimization of desirable properties of MSPP, the RSM approach provided empirical evidence for the existence of the suggested adsorption interaction, as adsorption increased with increment in magnetite content and degree of crosslinking of the MSPP nanocomposite which were responsible for π-cation and π-π interactions, respectively. The adsorption/desorption profile of MSPP indicated multiple potential applications beyond water treatment. Aside incorporation of magnetic separation, the regenerability, cheap, and sustainable nature of starch precursor confers a comparative cost advantage to the developed polymer. Considering its effectiveness in both simulated and real-time wastewater samples, MSPP holds great promise for commercialization of starch-based polymer adsorbents beyond decontamination applications.