Application of Ozone Related Processes to Mineralize Tetramethyl Ammonium Hydroxide in Aqueous Solution

Abstract

Tetramethyl ammonium hydroxide (TMAH) is an anisotropic etchant used in the wet etching process of the semiconductor industry and is hard to degrade by biotreatments when it exists in wastewater. This study evaluated the performance of a system combined with ultraviolet, magnetic catalyst (SiO2/Fe3O4) andO3, denoted as UV/O3, to TMAH in an aqueous solution. The mineralization efficiency of TMAH under various conditions follows the sequence: UV/O3> UV/H2O2/O3>H2O2/SiO2/Fe3O4/O3>H2O2/O3>SiO2/Fe3O4/O3>O3> UV/H2O2. The results suggest that UV/O3process provides the best condition for the mineralization of TMAH (40 mg/L), resulting in 87.6% mineralization, at 60 min reaction time. Furthermore, the mineralization efficiency ofSiO2/Fe3O4/H2O2/O3was significantly higher than that ofO3,H2O2/O3, and UV/H2O2. More than 90% of the magnetic catalyst was recovered and easily redispersed in a solution for reuse.