An effective method for improving electrocoagulation process: Optimization of Al13 polymer formation

• Al13 polymer formation in EC process are investigated.
• Al13 species fraction positively correlated with removal of turbidity and organic.
• pH 5–7 and lowering j favored the formation of Al13 polymer.
• Al13 fraction can reach more than 60% under optimal EC conditions.

Al13 polymer has been believed to be the most active species responsible for coagulation. The character of Al species distribution and the formation of Al13 polymer in electrocoagulation (EC) process were investigated in order to provide insight into optimizing EC operation and design. The results indicated that predominant Al species shifted from monomer toward medium polymer then to larger polymer or Al(OH)(s) with increasing EC time. The in-situ Al13 polymer could be generated in EC process, and became the dominant species during 5–15 min. In EC process, Al13 species fraction positively correlated with the removal of turbidity and organic. The increase of pH and current density could accelerate the hydrolysis-polymerization process of Al3+. pH 5–7 and lowering current density favored the formation of Al13 polymer during EC process, EC process with bipolar electrodes had a higher yield of monomeric and Al13 species, while EC process with monopolar electrodes facilitated the formation of larger polymer or Al(OH)(s). The content of Al13 polymer can reach more than 60% under optimal conditions.

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