Abstract
A countercurrent extractor (204φ × 4,260mm) was designed to remove organic pollutants from aqueous solutions by supercritical carbon dioxide and the optimum operating conditions were studied and the method was subsequently evaluated. Aqueous solutions containing dissolved aromatic nitro-compounds were treated by 9.81 × 106 Pa supercritical carbon dioxide at 35°C. A high removal efficiency was attained by filling up the whole space of column with the continuous aqueous phase using a differential pressure gauge to control the interface level of aqueous phase. 100 and 400 mg·l-1 of nitrobenzene (NB) aqueous solutions were treated at space velocity (SV) of 1.5 or 4.0 h-1. The residual ratio of NB in effluent water was not influenced by SV, but influenced by the concentration of NB in influent water and the ratio of solvent to feed (S/F value). When SV was below 4.0 h-1, 100 and 400mg·l-1 of NB could be removed sufficiently from the aqueous solution at 0.55 and 0.7 of S/F value, respectively. O-nitrophenol could be removed in the same order as NB, and o-nitrotoluene could be removed much more than both.
