Oligomerization of aniline catalyzed by Iron-tetraamidomacrocyclic ligand (Fe-TAML) near neutral pH

Aniline is a nitrogen-containing compound that contributes to both total organic carbon (TOC) and total nitrogen (TN) in wastewaters. Herein, we focus on converting aniline into oligomers, which aggregate into solid particles and can be separated from the wastewaters. By using this strategy, we can remove not only aniline but also TOC and TN in the wastewater without producing any secondary wastes. In this reaction, aniline is first reacted with H2O2 in the presence of Iron-tetraamidomacrocyclic ligand (Fe-TAML) near a neutral pH. Only 800 ppm of H2O2 and 2 ppm of Fe-TAML are needed to react with 1000 ppm of aniline at pH 8. After 2 days of reaction, solid particles are produced, and they can be filtered out with a membrane. The treatment efficiency can be further improved by lowering the pH to 6. Under this condition, the solid particles are big enough to settle under gravity in one day. After that, the top-layer solution can be separated from the solid particles. Following the oxidation- settling strategy, aniline, TOC, and TN of the decanted solution are reduced to 27.0, 99.0, and 29.0 ppm, respectively. This new strategy is effective in aniline removal with minimal H2O2 and catalyst usages.