Statistical optimization of removal of nitro-body compounds from spent acid of toluene nitration process

The removal of nitro-body compounds from spent acid of toluene nitration process was made by two methods of extraction by ethyl acetate solvent and adsorption by activated carbon particles. In extraction method, three parameters of spent acid sample volume, volume of extracting solvent and the amount of water for dilution of samples were statistically modelled and optimized using mixture design of experiments by Minitab 17 software. In the optimized conditions, the mean of extraction efficiency was obtained 98.5 +/- 1.4 wt.% in one step of extraction. Also, the treatment of spent acid for removal of nitro-body compounds by activated carbon adsorbent was optimized using Taguchi method by Minitab 17 software. The optimized values for three variables of shuffle time of mixture, the amount of adsorbent and the dilution times of sample are obtained respectively, 90 min, 0.1 g/L and 10 times by the statistical analysis of Taguchi design. The removal efficiency was resulted 87.5 +/- 2.6 wt.% of nitro-body compounds by using activated carbon adsorben. The advantages of proposed methods for the elimination of organic containments in waste acid of trinitrotoluene production process were the safety, simplicity, inexpensive, availability and industrialization.