Abstract
Nitrogen-containing wastewater is an important issue in optoelectronic and semiconductor industries. Wastewater containing nitrogen compounds such as ammonium, monoethanolamine (MEA), and tetramethylammonium hydroxide (TMAH) must be properly treated due to concerns about health and environmental effects. MnCe-GAC (granular activated carbon) processes were developed in this study for the treatment of TMAH-contaminated wastewater in high-tech industries. The MnCe-GAC processes could effectively remove ammonium, MEA, and TMAH from aqueous solutions. The removal efficiencies of ammonium and MEA by these processes were better than observed for TMAH. Parameters affecting TMAH removal such as type of process, type of wastewater (synthetic or real), pH, salts, and t-butanol were investigated. In general, removal efficiencies of TMAH by various processes were in the following order: MnCe-GAC/O3/H2O2 > MnCe-GAC/O3 > MnCe-GAC/H2O2 > MnCe-GAC > GAC. The negative effect of sulfate and nitrate on pollutant removal might be due to the salting-out effect. Based on t-butanol experiments, the main degradation mechanisms of TMAH by the MnCe-GAC/O3/H2O2 process likely involved hydroxyl radicals. The process proposed in this study could be an effective alternative method for the treatment of high-tech industrial wastewater to meet the new TMAH discharge limit.
Highlights
Nitrogen-containing wastewater is an important issue in high-tech industries such as optoelectronic and semiconductor manufacturing industries
Both synthetic and real wastewater (Plant 3) samples were treated by the above processes
A vessel (500 mL) was filled with known concentrations of a target solution with pH adjusted to the desired values (3, 7, or 11), and the solution was circulated through the column as indicated in Samples were collected, filtered, and analyzed in triplicate within acceptable analytical error (±5%)
Summary
Nitrogen-containing wastewater is an important issue in high-tech industries such as optoelectronic and semiconductor manufacturing industries. In thin-film transistor liquid crystal display (TFT-LCD) manufacturing processes, wastewater containing high concentrations of nitrogen compounds (such as ammonium (NH4 + ), monoethanolamine (MEA), or tetramethylammonium hydroxide (TMAH)) is generated [1,2]. TMAH is a caustic developing fluid, widely used in the manufacture of TFT-LCD and light emitting diodes (TFT-LED) and in semiconductor industries as a developer or etchant [2,3,4]. A TFT-LCD factory (sixth generation) could generate. 30,000 cubic meter per day (CMD) of TMAH-containing wastewater [5].
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