A Polyurethane-Based Composite Hydrogel as Functional Support for Metal Nanoparticles: An Efficient Catalyst and Antibacterial Agent
摘要
Dye-polluted industrial wastewater is often discarded into water sources, harming the environment and human life. Thus, there is an immediate need to treat dye-polluted wastewater to make it reusable and avoid its negative impacts on the environment. To address this problem, we reported the synthesis of polyurethane-alginate (PUT-NaL) composite hydrogel by the casting method and its use for the fabrication of Au/Ag bimetallic nanoparticles by the in-situ reduction method. PUT-NaL hydrogel and Au/Ag@PUT-NaL nanocomposite hydrogel were characterized by UV–visible, Fourier transform infrared spectroscopy, thermogravimetric analysis, field emission scanning electron microscopy, and energy-dispersive X-ray analysis. The surface plasmon resonance band appeared at 415 nm in the UV–visible spectra, indicating the presence of Au/Ag bimetallic nanoparticles in the hydrogel matrix. Here, Au/Ag@PUT-NaL nanocomposite hydrogel was used as a catalyst for the reduction of toxic dyes such as rhodamine B (RhB), Congo red (CR), and 4-nitrophenol (4-NP). The catalytic reduction of RhB, CR, and 4-NP was completed in 7 min, 14 min, and 8 min, with the apparent rate constants (kapp) found to be 0.701 min−1, 0.657 min−1, and 0.319 min−1, respectively, while using NaBH4 as a reducing agent. A binary mixture of dyes, such as CR and 4-NP or RhB and 4-NP, turned colourless in 11 min and 19 min, respectively. This indicates that a mixture of multiple dyes takes longer to completely reduce due to the availability of a fixed number of catalytic active sites compared to the greater number of available dye molecules. Dye-polluted textile industry wastewater also became colourless in 7 min upon the addition of the Au/Ag@PUT-NaL catalyst and a reducing agent. Au/Ag@PUT-NaL nanocomposites also demonstrated good antibacterial activity against ZD1 Ralstonia spp., with a 29 mm zone of inhibition among all tested bacteria. Thus, Au/Ag@PUT-NaL nanocomposite hydrogels can be used to design nano-filters to treat wastewater polluted with different dyes and microbes.