Removal of a disperse red dye from synthetic wastewater by chemical coagulation and continuous electrocoagulation. A comparative study

The effectiveness of chemical coagulation (CC) was compared to electrocoagulation (EC) with aluminium electrodes for decolourization purpose of a synthetic textile wastewater containing a disperse red dye. For CC, ferric chloride FeCl3 and aluminium sulphate Al2(SO4)3 as the coagulant were compared: the respective effects of initial pH, coagulant dosage, initial dye concentration, ionic strength and mixing conditions were investigated in order to maximize decolourization yield. The comparison between CC and EC is based on recently published data on EC by the same authors. Experimental results showed first that Al2(SO4)3 was far more effective than FeCl3 for colour removal using CC, regardless of operating conditions. A removal yield higher than 90% could be achieved with a 40 mg/L dose of Al2(SO4)3 18H2O in a large range of pH from 4 to 8 and for a dye concentration up to 235 mg/L. The removal yield could however be enhanced up to 95% using EC for pH values between 6 and 9 at the expense of higher operating costs. Nevertheless, EC presented the additional advantages to be more robust against pH change and to reduce simultaneously equipment costs in comparison to CC.

Research Highlights
► Chemical (CC) and electrocoagulation (EC) were studied.
► CC and EC were compared for the decolourization of textile wastewater.
► Alum was more effective than ferric chloride as a chemical coagulant.
► EC using Al electrodes was more effective than CC.
► EC required higher operating costs, but lower equipment costs.