A continuous-flow sparged packed-bed electrocoagulator for dye decolorization

• Gas sparging was used as stirring mechanism for mass transfer in packed-bed anode.
• Continuous gas sparging lowered the circuit R and residual dye concentration.
• Current flow ratio was the control parameter in electrocoagulator (EC) operation.
• Gas sparging decoupled effectiveness in mass transfer from the varying flowrates.
• Operation of the sparged packed-bed EC powered by PV energy was illustrated.

A sparged packed-bed electrocoagulator was developed for decolorization of dye wastewater. The anode of the electrocoagulator was a perforated polyvinyl chloride (PVC) pipe packed with iron nuts. At the center of each anode, a gas sparging tube was installed, and the hydrogen generated from the oxidation reduction reactions was recycled back to the reactor as the sparging gas. When running with a DC power supply, the operation of the packed-bed electrocoagulator with gas sparging can both enhance the decolorization efficiency and reduce the resistance and the energy consumption of the operation. When running with a photovoltaic (PV) panel, the wastewater feed flowrate was adjusted in response to the varying PV output current. The gas sparging was found to help enhance mass transfer rates of the electroactive ions to the bulk solution, and to make the decolorization efficiency independent of the varying feed flowrates.

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