Preparation of composite materials of NiAl-LDHs@WSF and study of their adsorption properties for Congo Red

In order to improve the utilization rate of waste silk fibers and reduce the harm of dyeing wastewater, a composite material was prepared by physical crosslinking using waste silk fibroin (WSF) and nickel aluminum hydrotalcite layered double hydroxides (NiAl-LDHs) as raw materials. In this work, the composite material was used to adsorb Congo Red (CR) from dye wastewater, which is a typical dye representative. Meanwhile, this composite material underwent characterization tests including scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and Brunauer–Emmett–Teller (BET) surface area measurements. The research results indicate that the composite material possesses the unique nanostructure of NiAl-LDHs, anion exchange properties, and biocompatibility of silk fibroin extracted from waste silk fibers. Adsorption experiments showed that CR removal by NiAl-LDHs@WSF followed a quasi-second-order kinetic model and Langmuir isotherm model, indicating monolayer adsorption. Under conditions of pH = 3 and temperature 308 K, 0.02 g adsorbent achieved a maximum capacity of 746.6 mg/g within 2 h. The preparation of NiAl-LDHs@WSF and study of its dye adsorption properties will open up new paths for the recycling and sustainable development of waste silk fibers, and provide effective measures to alleviate the shortage of raw material resources in the textile industry.