The acid dye intermediates 1-diazo-2-naphthol-4-sulfonic acid wastewater treatment by using solvent (trialkylamine N-235) extraction, and the raffinate treatment by hydrogen peroxide catalytic oxidation were studied. The extraction and stripping conditions were tested and the optimum process parameters were obtained. In addition, the multistage countercurrent extraction and stripping experiments were carried out. The results showed that the single stage extraction rate was higher than 82%, decoloration rate was 95%; the single stage stripping rate was higher than 91%; the two stages countercurrent extraction rate reached 93%, the five stages countercurrent stripping rate reached almost 100%. After hydrogen peroxide catalytic oxidation, the solution was achromatic, and the COD of the effluent was below 100 mg/l (the first-order national discharge standard). (C) 2004 Elsevier B.V. All rights reserved.