Removal of organic pollutants from mononitrotoluene (MNT) wastewater by reduced pressure distillation

• Reduced pressure distillation was introduced to remove organic pollutants from mononitrotoluene (MNT) wastewater.
• Majority of the organic pollutants were removed after reduced pressure distillation.
• When the distillation temperature was 60 °C, 98.9% of COD was removed and 99.5% of acute toxicity was reduced.

Mononitrotoluene (MNT) wastewater is a kind of explosive wastewater generated from MNT production, which is toxic and poorly degradable. The reduced pressure distillation was introduced to remove the organic pollutants from this wastewater. The effect of distillation temperature on chemical oxygen demand (COD) removal was studied. The chemical changes of MNT wastewater before and after distillation were evaluated by using UV–Vis spectroscopy, Gas Chromatography/Mass Spectroscopy (GC/MS) and Fourier Transform Infrared Spectroscopy (FTIR). The acute toxicity of MNT wastewater and its distillate was evaluated by bacterium bioluminescence assay using a freshwater bacterium Vibrio-qinghaiensis sp. Nov. The results indicated that the main organic components in MNT wastewater were three mononitrotoluene isomers (2-nitrotoluene, 3-nitrotoluene, 4-nitrotoluene) and benzoic acid, 2-methyl-3,5-dinitrophenol, 4-methyl-2,6-dinitrophenol and 1,3-benzenediol. The majority of the organic pollutants were separated from MNT wastewater after distillation. The removal efficiency of COD increased with decreasing temperature, when the temperature was 60 °C, 98.9% of COD was removed and 99.5% of acute toxicity was reduced.