Application of an ozone-activated peroxymonosulfate process to effectively degrade tetramethylammonium hydroxide (TMAH) in semiconductor wastewater

In this study, ozone-activated peroxymonosulfate (O3/PMS) was used to remove tetramethylammonium hydroxide (TMAH) from artificial semiconductor wastewater. The rate constant for the O3/PMS process was approximately 14.4 times higher than that for the process employing only O-3. This was attributed to the explosive production of hydroxyl radicals (center dot OH) in the process, the contribution of which was confirmed using a scavenger test. The degradation efficiencies were the highest at pH 7.0 (1.80 x 10(-2) min(- 1) ) and 40 degrees C (2.18 x 10(-2) min(- 1) ). Alkalinity and humic acid, which are potent scavengers of center dot OH, significantly reduced the degradation of TMAH. Remarkably, removal efficiencies of 64.4 % for TMAH and 43.7 % for the total organic carbon (TOC) were achieved at a relatively high initial concentration of 100 mu M. However, approximately 27 % of the nitrogen was converted to the final byproducts, NH4+ and NO3- , indicating that a considerable number of nitrogen fragments remained as intermediates. Degradation pathways and intermediates were proposed based on the spectrometry data. Given that the toxicity of the demethylated intermediates was roughly 20-30 times lower than that of TMAH, the acute toxicity to A. fischeri was reduced by approximately half (46.4 f 2.57 %). The results of this study demonstrated the substantial potential of the O-3/PMS 3 /PMS process for treating wastewater containing TMAH.