Functionalization of the magnetite nanoparticles with polysilsesquioxane-bearing N- and S-complexing groups to create solid-phase adsorbents

Sol–gel method based on the reaction of hydrolytic co-polycondensation of alkoxysilanes was applied to obtain composites of magnetite and silica with amino and mercapto functional groups of core–shell structure. Magnetite core ensures easy removal of materials from solutions in a quick and effective way with a help of a magnet. Using 1,2-bis(triethoxysilyl)ethane as a structure-forming agent (instead of traditional tetraethoxysilane) allowed synthesis of mesoporous samples with well-developed porous structure (specific surface area values of 400–800 m2/g). In combination with high content of available functional groups, introduced to the process of one-pot synthesis using 3-aminopropyltriethoxysilane and 3-mercaptopropyltriethoxysilane as functionalyzing agents, it endowed the synthesized composites with high sorption capacities to silver(I), copper(II), and lead(II) ions. Meanwhile, the affinity to the molecules of dyes (Acid Red 88 and Methylene Blue) was shown to be in direct correlation with the composites’ surface charges and uptake can reach 118 mg/g and 88 mg/g, respectively. These results indicate the possibility of magnetite nanoparticles’ one-step functionalization with mesoporous silica layers and simultaneous introduction of different functional groups. Such properties make them very attractive for application in adsorption technologies as effective adsorbents of metal ions as well as organic pollutants.