An effective method for improving electrocoagulation process: Optimization of Al 13 polymer formation

Abstract

h i g h l i g h t s• Al 13 polymer formation in EC process are investigated.• Al 13 species fraction positively correlated with removal of turbidity and organic.• pH 5-7 and lowering j favored the formation of Al 13 polymer.• Al 13 fraction can reach more than 60% under optimal EC conditions. Keywords: Electrocoagulation Aluminum species Electrochemical parameter a b s t r a c t Al 13 polymer has been believed to be the most active species responsible for coagulation. The character of Al species distribution and the formation of Al 13 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 Al 13 polymer could be generated in EC process, and became the dominant species during 5-15 min. In EC process, Al 13 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 Al 3+ . pH 5-7 and lowering current density favored the formation of Al 13 polymer during EC process, EC process with bipolar electrodes had a higher yield of monomeric and Al 13 species, while EC process with monopolar electrodes facilitated the formation of larger polymer or Al(OH) (s) . The content of Al 13 polymer can reach more than 60% under optimal conditions.

Enhanced efficiency in HA removal by electrocoagulation through optimizing flocs properties: Role of current density and pH

“…The results of BET analysis implied that the flocs generated at low initial pH may have more surface adsorption sites, which would make EC perform better at low pH condition. Moreover, in-situ Al 13 polymer could be generated in EC process, and became the dominant species at about 5 min in the weak acidic pH condition [23]. The flocs generated from Al 13 polymer showed a larger flocs size and a rougher surface structure than other Al species [21].…”

“…5e), and it was consistent with the results of BET analysis. According to our previous results [23], low j and weak acidic water conditions favored the formation of in-situ Al 13 polymer. A lot of studies [20,21] have demonstrated that the flocs generated from Al 13 polymer are looser and more porous surface.…”

Chromium ion removal from raw water by magnetic iron composites and Shewanella oneidensis MR-1

“…In situ , trivalent iron is formed by hydroxylation, forming Fe (OH) 3 . The iron oxidation and Cr (VI) reduction reactions are favoured at low pH 46 . The formation of a pH-lowering microenvironment on the colloidal surface (Pac-02) and a proton-transferring microinterface process can control the formation of intermediates with different degrees of polymerization of Al through Al(OH) 3 + H + , and the cationic polymer polyacrylamide (PAM) could be used as a coagulant aid 47 .…”

Effects of some ion-specific properties in the electrocoagulation process with aluminum electrodes

“…It justifies why supporting electrolytes in electrocoagulation studies should contain a chaotrope anion rather than a kosmotrope anion to allow a favorable release of aluminum cations. + after sufficient aging [37,38]. For pH values lower than 5, A l 3+ cations are the sole ionic species in aqueous phase, they gradually disappear in favor of cationic hydroxides in the pH range 5-7.5.…”