Recovery of aniline from wastewater by nitrobenzene extraction enhanced with salting-out effect.

OBJECTIVE Nitrobenzene extraction enhanced by salting-out effect was employed to recover aniline from wastewater at 25 degrees C. METHOD Batchwise experiments were conducted to elucidate the influence of various operating variables on the extracting performance, including acidity of wastewater, initial aniline concentration, ratios of solvent to wastewater, extraction stages, concentrations and different types of inorganic salts, such as NaCl, KCl, Na(2)SO(4), CaCl(2) and K(2)SO(4). RESULTS Nitrobenzene with a concentration of 20% and a pH value of 9.1 at the temperature of 25 degrees C together with NaCl of a concentration of 14 wt.% realized nearly 100% aniline recovery at the fifth stage of wastewater treatment. CONCLUSIONS High pH values and volume ratios of nitrobenzene/wastewater are more suitable for recovery of aniline. In addition, recovery of aniline is significantly elevated with increase of the concentration of salts, whose promoting effects are in the following order: NaCl>Na(2)SO(4)>K(2)SO(4)>CaCl(2)>KCl on the weight basis of wastewater. Furthermore, aniline in wastewater can be almost completely recovered by five-stage sequential nitrobenzene extraction, which is promoted continuously by the salting-out effect.