Removal of tetramethylammonium hydroxide (TMAH) in semiconductor wastewater using the nano-ozone H2O2 process

Abstract

In this study, we used a nano-ozone bubble to enhance the efficiency of the ozone/H(2)O(2 )process for the degradation of tetramethylammonium hydroxide (TMAH) found in semiconductor wastewater at high levels. The nano-ozone bubble significantly increased ozone mass transfer rate compared to that of the macro-ozone bubble. The half-life of nano-ozone bubbles was 23 times longer than that of the nano-ozone bubbles. Due to the high ozone mass transfer rate and its durability, the nano-ozone bubble increased the TMAH degradation rate compared to that of the macro-ozone. The addition of H2O2 significantly increased the TMAH degradation rate constant by (OH)-O-center dot production during the nano-ozone bubbles/H(2)O(2 )process. The optimum conditions for TMAH removal was 25 degrees C and pH 10. Within 90 min of the nano-ozone/H(2)O(2 )process, TOC removal was 65 % while 80 % of nitrogen was converted into nitrate (NO3) with 95 % of TMAM removal. Decreases in acute (40-fold) and chronic (2-fold) toxicity were achieved after applying the nano-ozone/H(2)O(2 )process to TMAH containing wastewater. However, there was no significant chronic toxicity decrease during the nano-ozone/H(2)O(2 )process of TMAH.