Plasma assisted-synthesis of magnetic TiO2/SiO2/Fe3O4-polyacrylic acid microsphere and its application for lead removal from water.

Hybrid microsphere of polyacrylic acid (PAA) grafted TiO2/SiO2/Fe3O4 (TSF-PAA) was synthesized via coating polyacrylic acid on the core-shell-shell TiO2/SiO2/Fe3O4 (TSF) structure with the aid of plasma technique. The synthesized microsphere was applied to remove Pb2+ from water. The state-of-the techniques including TEM, FTIP, TGA, and XPS were used to characterize the morphology and the surface functionalities of the microsphere and confirmed that PAA was successfully grafted on TSF surfaces and active functional groups were introduced. A combination of the BET, VSM, and XRD results showed that plasma treatment decreased surface area of TSF by 36%, whereas its magnetic property and crystalline structure were not significantly altered. Both the Pb2+-sorbed magnetic TSF and TSF-PAA can be separated with a magnet from the aqueous phase. The pH and dosage changes of the microspheres exerted an intense influence on their lead removal efficiency. Compared to TSF, the removal capacity of Pb2+ by TSF-PAA was considerably improved from 65% to 95%, attributable to the fact that PAA coating induced by plasma treatment additionally introduced carboxylic and hydroxyl groups to TSF. Their introduction greatly enhanced the interaction between Pb2+ and TSF-PAA relative to that with TSF, which had hydroxyl groups only as supported by XPS analysis.