Solvent sublation of Toluene from aqueous phase

Solvent sublation, a surface chemical technique, was used to remove toluene from aqueous solution into a layer of paraffin oil. Analytical methods for GC determination of toluene in both gas and aqueous phase were set up. The comparison of solvent sublation and conventional air stripping on toluene removal was carried out. It was found that solvent sublation provides significant improvement over air stripping in removing toluene from water, and reduces toluene emission to the atmosphere. The toluene emissions reduction by solvent sublation are 30%-70% under different conditions. The effects of air flowrates and thickness of organic layer were studied. Increased air flowrate enhanced the efficiency of toluene removal from water. It took less than 1 hour to remove 90% of the toluene from water at a high flowrate (60, 94 ml/min). However, it was also found that increased air flowrate (from 32 ml/min to 94 ml/min) increased the toluene emission to the air (from 29% to 66%). Toluene removal appeared independent of thickness of organic layer. In contrast, more organic solvent could reduce toluene emission to the air. The toluene emission reduction was about 60% when the thickness of organic layer was 20mm. Added surfactants (sodium lauryl sulfate and hexadecyltrimethylammonium bromide) and organic solvent (ethanol) can also improve the efficiency of toluene removal, since they reduce the surface tension of the solution and consequently reduce air bubble size. Our study on toluene emission reduction by solvent sublation is the first systematic investigation in this area