Coating of magnetite with mercapto modified rice hull ash silica in a one-pot process

Abstract

In this research, mercapto-silica coated magnetite (Fe3O4-SiO2-SH) has been prepared in aqueous solution through a simple approach so called a one-pot process. The Fe3O4-SiO2-SH was prepared in nitrogen condition by mixing magnetite, 3-mercaptopropyltrimethoxysilane (MPTMS), and sodium silicate (Na2SiO3) solution extracted from rice hull ash, and adjusting the pH of 7.0 using hydrochloric acid. The residue was washed with deionized water, dried at 150°C and separated with an external magnetic field. In that work, the volume of MPTMS and Na2SiO3 was varied and the total amount of Si represented as silica was kept constant. Characters of the material including the functional group presence, the structure, the porosity, the morphology and stability toward various solvents were identified and evaluated. Results of characterization indicated that mercapto-silica has been coated magnetite particle with a simple one-pot process. Coating mercapto-silica on magnetite increases particle size, surface area, and chemical stability. Additionally, Fe3O4-SiO2-SH also shows high stability toward various organic solvents. The magnetic property of magnetite does not change after coating and the addition of nonmagnetic material still gives high value of maximum saturation magnetization. The presence of mercapto groups effective for interaction with heavy metal ions, the high chemical stability without removing the magnetic property promises the prospective application of Fe3O4-SiO2-SH in the future such as for separation and removal of heavy metal ions from aquatic environments.

Functionalization of Silica Coated on Iron Sand Magnetic Material with Diethylenetriamine

“…This by-product may be trapped in the coated magnetic material as an impurity. By using sodium silicate as the silica source, washing the precipitate is an important step to find the coated magnetite with free of unwanted byproduct [19]. Stability of coated magnetic material in acidic medium: The stability of synthesized product was tested against acid, since acid generally is used in adsorption and desorption of Au(III).…”

“…Modification of silica is typically accomplished through silanization reaction, yet requires long and tedious procedure through heating process. To overcome this problem, several studies with a simple technique of sol-gel process for modification of silica with functional groups have been reported [19,[27][28][29].…”

“…Dissolution by acid solution can be diminished by coating magnetic material with silica, as silica forms shell to protect magnetite core particles [2,19]. Magnetic material was completely dissolved in 1 M solution of HCl forming a yellow solution [ Fig.…”

“…The immobilization of functional groups on the silica surface is generally prepared through several processes, in which the silica gel is reacted with a compound containing a functional group in the medium of water-free toluene [2,16,19]. Modification of silica is typically accomplished through silanization reaction, yet requires long and tedious procedure through heating process.…”

“…Sources of magnetic material are able to be derived either from the precursor FeCl3·6H2O and FeCl2·4H2O [2,19,20], Fe(NO3)3·9H2O [21] or FeSO4·7H2O and Fe2(SO4)3·nH2O [22]. Several chemical methods can be used to synthesize magnetic material of iron oxides, including coprecipitation reactions occur in the mixture solution of Fe 2+ and Fe…”