Application of Chemical Coagulation Process for Direct Dye Removal from Textile Wastewater

Since some dyes and their metabolites have toxicity and carcinogenicity potential, and are dangerous to the health of different living creatures, discharge of untreated wastewaters containing large concentrations of dye compounds into water resources is one of the important environmental problems. Therefore, in this research, the efficiency of chemical coagulation process was investigated using ferric chloride coagulant to remove Direct Red 23 dye from colored wastewater.
In the experiments, a Jartest device was used and the effect of different parameters including the dose of the coagulant (20-200 mg/L), pH (3-10), and initial concentration of the dye (25-200 mg/L) on the efficiency of chemical coagulation process for removal of the dye was examined. Further, the final pH of the wastewater was investigated and the optimal conditions were determined.
The results indicated that the optimal dose of ferric chloride coagulant for Direct Red 23 dye removal of 97.7% is 40 mg/L at the optimal pH of 7. With increase in the dose of the coagulant, the dye removal efficiency increased, while the final pH of the wastewater decreased. Under constant conditions, with increase in the dye concentration, the dye removal efficiency diminished.
Chemical coagulation by ferric chloride is a very effective and fast method for removal of direct dye from colored wastewater.