Cleaner production processes in the synthesis of blue anthraquinone reactive dyes

One of the problems in reactive dye production is the soluble products which can pollute effluents, and which should not be discharged untreated into the open water. The production process of monochlorotriazine reactive dyes was studied using an anthraquinone reactive blue as a model. In order to decrease wastewater pollution, the production process was modified. The process stages were monitored using TLC. Different chromatographic systems were investigated; a selection of 12 chromatographic systems was made and it was established that the most favorable mobile phase for TLC of the investigated compounds was chloroform:isopropyl alcohol:ammonium hydroxide (2:4:1). Dye concentration in wastewater from the different synthesis procedures was determined spectrophotometrically. Process efficiency was estimated on the basis of production wastewater pollution. A coagulation/flocculation process was employed as a feasible method for the treatment of this type of wastewater. Optimal configuration of batch coagulation tank, applying rapid and slow mixing, was used. Inorganic coagulants (FeCl(3)6H(2)O and AlCl(3)6H(2)O) and a polymeric flocculant with 99.5% dye removal efficiency were used. On the basis of the experimental results, an economically more favorable and environmentally more friendly production procedure is postulated. (C) 1999 Elsevier Science Ltd. All rights reserved.