Separation and Recovery of Tetramethyl Ammonium Hydroxide with Mesoporous Silica Having a Hexagonal Structure (MCM-41)

Abstract

Separation and recovery of tetramethyl ammonium hydroxide (TMAH) was investigated using several types of MCM-41 (mesoporous silica having hexagonal structure) adsorbents. The MCM-41s were prepared by hydrothermal synthesis with structure-directing agents with different alkyl chains. The prepared MCM-41s were characterized with X-ray diffraction, transmission electron microscope, nitrogen gas adsorption, and zeta potential, and then used for adsorption of TMAH. The adsorption of TMAH with MCM-41s increased with pH up to pH ≈ 10 and then decreased as the MCM-41 dissolved. The adsorption of TMAH progressed via the Langmuir mechanism. The maximum adsorption corresponded to the pore diameter and the pore volume of the MCM-41s. MCM-41 also possesses selectivity for TMAH against phenol. The chromatographic operation was conducted using granulated MCM-41 to avoid excessive pressure-drop through the packed column and quantitative adsorption-elution processing of TMAH could be achieved.

Keywords:

• Ion exchange
• adsorptive separation
• tetramethyl ammonium hydroxide
• mesoporous silica

ACKNOWLEDGEMENT

The authors are grateful to Prof. Asaoka of The University of Kitakyushu (UoK) for his suggestion regarding the granulation of MCM-41, to Prof. Sakurai of UoK for zeta potential analysis, and to Prof. Lee and Mr. Mizutani of UoK for TEM analysis. The XRD and TEM measurements were performed at the Instrumentation Center of UoK. This work was supported by a Grant-in-Aid for Young Scientists (B) (No. 21760614) from the Japan Society for the Promotion of Science (JSPS).