Supercritical water oxidation: a breakthrough approach for remediation TNT-contaminated pink water

Abstract

ABSTRACT This study aimed to optimize the operating conditions of the supercritical water oxidation (SCWO) process for 2,4,6-trinitrotoluene (TNT)-containing pink water treatment. Lab-scale SCWO experiments were performed by varying the temperature (400–600°C), reaction time (45–180 sec), and oxidant ratio (100–300%). The performance of SCWO in terms of pink water treatment was evaluated using TNT and total organic carbon (TOC) removal efficiency, SCWO effluent toxicity, and generated by-products. The results showed that as temperature and residence time increased, the TNT and TOC removal efficiency increased due to solute-solvent reaction acceleration under SCWO conditions and long contact time between organic matter and oxidant. The optimal conditions for SCWO were identified as follows: a temperature of 500°C, a reaction time of 120 seconds, and an oxidant ratio of 150%. These conditions resulted in a TNT removal efficiency of 99.9% and a TOC removal efficiency of 93.5%. The by-products analysis results showed a relationship between operating temperature and the type of by-products produced. Various compounds such as toluene, nitrobenzene, TNT isomers, naphthalene, and simple alkane structures were formed. However, above 500°C, many of these species decomposed, giving rise to octadecanoic acid and 13- Docosenamide. The microbial toxicity test demonstrated that SCWO effluents showed no toxicity for all investigated SCWO conditions, demonstrating the superiority of the SCWO method for the toxicity removal of TNT-containing pink water.