Dye Extraction by Functionalized Magnetic Nanoparticles with Surfactants and Cyclodextrins through Specific and Host–Guest Interactions

Functionalized magnetic nanoparticles (NPs) were synthesized by using different surfactants and cyclodextrins (CDs) for the extraction of toxic dyes from the aqueous bulk at room temperature to exploit the surfactant/CD-dye interactions operating at the solid-liquid interface. The extraction of dyes was monitored by UV-visible studies and quantitatively estimated. Both hexamethylene bis(hexadecyl dimethylammonium bromide) (16-6-16) and tris(2-(N-dodecyl <i>N</i>,<i>N</i>-dimethylammonio)ethylamine) tribromide (TriCAT) functionalized magnetic NPs proved to be excellent extractors, whereas extraction was highly facilitated at high or low pH when CD-functionalized magnetic NPs were used. Self-association among the dye molecules impeded the extraction. A combination of both polar as well as nonpolar along with dye-dye interactions participated in the extraction. Quantification was carried out by performing surface analysis of dye-loaded magnetic NPs. FTIR and XPS identified the functionalities participating in the extraction, whereas TEM, FESEM, and their EDS analyses determined the elemental composition. The amounts of N and S acted as fingerprinting elements for the adsorption of dyes at the solid-liquid interface, whereas overall amounts of C and O qualitatively differentiated among the relative amounts of dyes extracted. All results concluded that the extraction was much facilitated for those dyes which demonstrated a low degree of self-association in aqueous bulk and a high degree of solid-liquid interfacial adsorption.