Adsorption of Tetramethylammonium Hydroxide on Activated Carbon

Abstract

Tetramethylammonium hydroxide (TMAH) is widely used in manufacturing thin-film transistor liquid crystal displays (TFT-LCD) and semiconductors. Because of its toxicity and nitrogen content, TMAH-containing wastewater has to be properly treated before discharge. In this study, several commercial activated carbons were characterized and used for TMAH adsorption. Activated carbon with micropores showed higher adsorption capacity for TMAH. The adsorption kinetics could be represented by pseudo-second-order model, and the Langmuir model fitted the adsorption of TMAH on activated carbon under different pH adsorption well. Higher pH was favorable for TMAH adsorption, while there was no TMAH adsorption at pH 4.7±0.2. The adsorption was spontaneous and exothermic. Exhausted carbon could be easily regenerated by 0.1 N HCl, with no considerable reduction in performance even after five cycles of adsorption-desorption. It was proposed that electrostatic interaction was the main mechanism of TMAH adsorption on the activated carbon.