This paper presents an experimental study on the carrier-mediated emulsion liquid membrane (ELM) separation of lignosulfonate (LS) from acidic aqueous solution. The ELM contains trioctylamine (TOA) as carrier, dichloroethane as solvent and polyethylene glycol (PEG) as surfactant. The fundamental parameters (viz. surfactant concentration, phase ratio, strip phase concentration, carrier concentration, treat ratio) affecting the separation of LS through the ELM were investigated to select the best combination of process parameters. The maximum separation of IS (about 91%) was achieved at a PEG concentration of 5% (w/v), strip phase concentration of 0.4 M NaOH and a phase ratio of 1:1. Extraction of LS increases with increase of strip phase and carrier concentration. The LS concentration in the feed has no considerable effect on the extraction process up to 378 mg l(-1). Beyond this limiting concentration the extraction decreases. The ELM process (PEG-TOA-dichloroethane) can efficiently extract LS from industrial black liquor. About 85-86% LS can be extracted at optimum condition. (C) 2010 Elsevier B.V. All rights reserved.