Technical Research On The Adsorptive Treatment By DRH Resin Of The Wastewater From Nitration And Alkaline Wash In TDI Production

The wastewater arising during the nitration and alkaline wash stage in the toluene diisocyanate manufacture was treated by adsorption with DRH-1 resin. The concentration of nitrobenzenes was 0.4~2.2%and the COD was 2.87 × 103~6.38×103mg/L in the original wastewater. As the result of the acidic sedimentation and resin-adsorption, the nitrobenzenes was reduced to a level of "not found", but the COD can't meet the standard. Moreover, the COD could steadily be retained below 200mg/L after a further Fenton reagent oxidation.The parameters were determined through test, such as flow rate of wastewater ,pH, volume of treated wastewater; tape,temperature and flowrate of regenerant.Under the optimun process conditions the working adsorption capacity of the resine adsorbent to COD was 70~80mg/ml.The remove rate of COD and nitrobenzenes was more than 90% and nearly 100%.The resin could be reused after its desorbing treatment,and a residual solution containing more than 50% intermediates for TDI production could be obtained from the desorption solution following the recovery of solvents by its distillation. Ethanol was highly concentrated in the former 2BV of regenerant washing water and can be recycled.