The separation of mineral salt from a dye-salt aqueous mixture by electrodialysis.

The efficiency of desalination of reactive dye solutions with the addition of a fixed amount of mineral salt was evaluated using standard ion-exchange membranes in the electrodialysis (ED) process. Five reactive dyes (Reactive Orange 16, Remazol Brilliant Blue R, Reactive Orange 20, Reactive Black 5, Reactive Red 120), varying in molecular weight, were used in the study. The model solutions were prepared by varying the dye concentration (20, 50 and 100 mg/L) and adding mineral salt (2 g/L of NaCl) to each dye solution. It was observed that the salt was successfully separated from dye solutions with the efficiency of 97.6%-98.5%. The migration of dye molecules from diluate to concentrate compartments was negligible. The dye concentration in the concentrate compartments amounted to 0.6-0.85 mg/L, irrespectively of the process parameters. However, significant deposition of dye particles in the membrane matrix was noted. Around 26%-31% of the initial dye mass was adsorbed, and this effect was strongly influenced by the dye reactivity. It can be concluded that the ED process with standard ion-exchange membranes is quite a promising method for reactive dye and mineral salt separation. This will enable further usage of the obtained dye and salt streams in a variety of technological processes. [ABSTRACT FROM AUTHOR]