Treatment of Semiconductor Wastewater Containing Tetramethylammonium Hydroxide (TMAH) Using Nanofiltration, Reverse Osmosis, and Membrane Capacitive Deionization

As the semiconductor industry has grown tremendously over the last decades, its environmental impact has become a growing concern, including the withdrawal of fresh water and the generation of harmful wastewater. Tetramethylammonium hydroxide (TMAH), one of the toxic compounds inevitably found in semiconductor wastewater, should be removed before the wastewater is discharged. However, there are few affordable technologies available to remove TMAH from semiconductor wastewater. Therefore, the objective of this study was to compare different treatment options, such as Membrane Capacitive Deionization (MCDI), Reverse Osmosis (RO), and Nanofiltration (NF), for the treatment of semiconductor wastewater containing TMAH. A series of bench-scale experimental setups were conducted to investigate the removal efficiencies of TMAH, TDS, and TOC. The results confirmed that the MCDI process showed its great ability as well as RO to remove them, while the NF could not make a sufficient removal under identical recovery conditions. MCDI showed higher removals of monovalent ions, including TMA+, than divalent ions. Moreover, the removal of TMA+ by MCDI was higher under the basic solution than under both neutral and acidic conditions. These results were the first to demonstrate that MCDI has significant potential for treating semiconductor wastewater that contains TMAH.