Magnetic mesoporous silica for water remediation: Synthesis, characterization and application as adsorbent of molecules and ions of environmental concern

Abstract

Magnetic mesoporous silicas (NSMSiO2) were synthesized by coating nano-sized magnetite (NSM) particles with mesoporous silica shells. The effects of the NSM loading on the morphology, charge development and adsorption properties of the synthesized composites were investigated. Both the shape and the size of aggregates strongly changed as NSM/SiO2 molar ratio increased, i.e., from plates to spherical-like particles, in agreement with reduction on the silica shell thickness. The shell acted as a protective agent that minimized alteration of the magnetite structure and avoided magnetite dissolution in acidic media. The composites have a significant adsorption capacity towards a humic acid and the cationic dye malachite green, showing that they can adsorb both, anionic and cationic species. HA seems to enter the pores and bind the NSM cores, whereas malachite green binds mainly the silica shell. The effect of Ca2+ concentration on the adsorption capacity of the synthesized composite was also evaluated and discussed. The magnetic property of the materials facilitates the recuperation of the adsorbent from aqueous environments.