Reclamation of wastewater using composite coagulants: A sustainable solution to the textile industries

The present study was aimed to investigate the effectiveness of a composite coagulant {magnesium chloride (MC) added with aluminum chlorohydrate (ACH)} for the treatment of simulated as well as real textile wastewater. Simulated textile wastewater was prepared using three different categories of dyes namely, Reactive Black 5 (RB5), Congo Red (CR) and Disperse Blue 3 (DB3) in the tap water along with other chemical additives. The optimum pH for the composite coagulant was 12 at which 90 % decolourisation efficiency was obtained when both the coagulants were used in equal ratio with a combined dosage of 800 mg L^-1. Out of the three different coagulant dosing methods, namely, MC+ACH, ACH+MC and MC-ACH, MC+ACH at the ratio of 1.5:1 with a combined dosage of 800 mg L^-1 was found to be the best combination, at which almost complete colour removal was achieved. The effectiveness of the composite coagulant was also verified with real textile wastewater. For real textile wastewater, 95 % decolourisation efficiency was obtained at just 1000 mg L^-1 of combined MC+ACH (1.5:1) dosage. Adsorption and charge-neutralisation along with sweep-flocculation were proposed as the predominant colour removal mechanisms.