Sol-gel derived Fe3O4 quantum dot decorated silica composites for effective removal of arsenic (III) from water

Iron oxides are getting attention for the removal of toxic arsenic from water. However, the lower surface area and stability of iron oxides are the major concerns. One of the important strategies to overcome the above drawbacks could be by generating zero-dimensional quantum dots (QDs) of iron oxides and making composite with materials having higher surface area. In present work, we report efficient Fe3O4 quantum dot decorated silica (FS) adsorbent prepared by facile sol-gel method under different reaction conditions. The structural morphology, phase purity and physico-chemical properties of the composite are thoroughly investigated. It is found that nano-size of the composite is only formed under a particular condition. High resolution transmission electron microscope clearly shows the formation of Fe3O4 quantum dots (average size of 3-4 nm) with the organically modified silica surface. Among the prepared composites, FS-3 shows best arsenic removal efficiency (38.2 mg g(-1)), which is higher than pure Fe(3)O(4 )and silica particles as well as many other reported composites. Moreover, the adsorption study fit well into pseudo-second order kinetics. The high adsorption capacity of FS-3 could be expected due to improve stability of Fe3O4 due to its QD size, synergistic effect of Fe3O4 QD and silica nanoparticles as well as the improved surface area and pore volume of the composite, increasing effective number of active sites for the adsorption. Fe3O4 and silica both are environmentally sustainable; hence, they could be a potential adsorbent for arsenic removal in near future.