Recovery of high purity sulfuric acid from the waste acid in toluene nitration process by rectification

► Rectification was introduced to recover high purity sulfuric acid from waste acid. ► The waste acid was purified and concentrated synchronously by rectification. ► 94% of COD and nitro aromatic compounds in the waste acid were removed. ► High purity sulfuric acid with concentration reaching 98.2 wt.% was recovered.