Novel baffled configuration of electro-coagulation?flotation process for treatment and fate of Direct Blue 71: Sludge characteristics and process optimization

In this study, electro-coagulation-flotation process was investigated in the new baffled reactor to use the advantage of simultaneous flotation in an individual compartment to eliminate the need of separate chamber for flotation. The middle baffle led to the production of larger and denser flocs and consequently, settling velocity, sludge volume index, and floc density increased by 63%, 13%, and 14%, respectively. Effective parameters of electro-coagulation-flotation process in the proposed reactor were optimized due to treatment of Direct Blue 71. In the optimal condition ([dye]=200 mg/L, electrical conductivity=6.7 mS/cm, current density=3.54 mA/cm(2), and pH=8 in 60 min), the removal efficiency of dye, naphthalene ring, COD, and TOC, average current efficiency, energy and anode consumption, operation cost, sludge settling velocity, and floc density were 99.4%, 73%, 39%, 50%, 0.85, 0.54 kWh/m(3), 0.24 kg/m(3), 0.15 $/m(3), 5.43 cm/min, and 3.86 kg/m(3), respectively. In this condition, the seven compounds of sulfamic acid, benzene, naphthalene-2-sulfonic acid, xylene, 2,6-Diamino-1-naphthol, 3,7-diamino-4hydroxynaphthalene-2-sulfonic acid, and 1,5-Naphthalenedisulfonic Acid were detected as the by-products of DB71. Based on the toxicity estimation, electro-coagulationflotation process in the new reactor by a reduction of 99.9% toxicity, has the potential of converting hardly-biodegradable and toxic dye wastewater to colorless and nontoxic wastewater. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

In this study, the electro-coagulation-flotation process was investigated in a new baffled reactor to optimize parameters for the treatment of Direct Blue 71. The process achieved high removal efficiency of dye and identified seven compounds as by-products. It has the potential to convert toxic dye wastewater into colorless and non-toxic wastewater by reducing toxicity by 99.9%.