Recovery of nitrotoluenes in wastewater by solvent extraction

Toluene extraction was utilized to recover 2,4-dinitrotoluene (DNT), 2,6-DNT, and 2,4,6-trinitrotoluene (TNT) from wastewater of toluene nitration process. The batch-wise experiments were performed to elucidate the influence of various operating variables on the extracting behavior, including extracting temperature, volume ratios of solvent versus wastewater, agitation time, acidity of wastewater, and extraction stages. It was found that recovery of total organic compounds (TOC) was significantly elevated with increasing extraction temperature. Besides, high volume ratio of toluene/wastewater (2.0) and wastewater acidified to lower pH value enhanced the recovery percentage of TOC, in which extractable tendency was as follows: 2,6-DNT > 2,4-DNT > 2,4,6-TNT. It is worth noting that the nitrotoluenes in wastewater would be almost completely recovered using three sequential stages toluene extraction at the agitation time of 12 min and pH 3.0. It is apparent that this established method is promising for the treatment of wastewater from toluene nitration processed industrially.