Magnetic composite sponges based on chitosan and whey protein modified magnetite nanoparticles for dye removal from water.

In this work, a novel application of whey protein isolate (WPI) for surface coating of magnetic nanoparticles (MNPs) is demonstrated. WPI-modified MNPs (WPI-MNPs) were prepared via chemical co-precipitation of ferrous and ferric salts. A mixture of chitosan and MNPs (or WPI-MNPs) was subject to lyophilization to produce magnetic composite sponges (designated as Chi-MNPs, and Chi-WPI-MNPs, respectively). Scanning electron microscopy (SEM) images clearly show improvement in dispersibility of WPI-MNPs on Chi-WPI-MNPs compared to the uncoated samples. The saturation magnetization profiles of all MNP samples, which were measured by a vibrating sample magnetometer (VSM), show superparamagnetic properties. The pore structure determined by mercury intrusion porosimeter (MIP) reveals a larger average pore size for Chi-WPI-MNPs compared to Chi-MNPs. The percentages for methylene blue (MB) dye removal of Chi-WPI-MNPs increased by 23.3% and 12.7% when compared to those of neat and Chi-MNPs sponges, respectively. The adsorption isotherms of all sponges can be described by both Langmuir and Freundlich models. The sponge containing WPI-MNPs could be reused with a 23.7% reduction in adsorption efficiency after 4 cycles of use. [ABSTRACT FROM AUTHOR]