Electrocoagulation (EC) is an electrochemical water treatment process used by a variety of industries. The process destabilizes and aggregates contaminant particles, ions such as heavy metals, and colloids, using an electrical charge to hold them in solution. The process traditionally utilizes an anode and a cathode, stimulated by a DC power source to destabilize the charges. This operation separates flocculated materials from water, allowing those materials to be removed, leaving clear water.

HOW DOES EC WORK?

Traditionally, the electrochemical process electrolytically oxidizes a sacrificial anode to release metal ions that form coagulants, destabilizing contaminants, and breaking emulsions. This coagulation forms flocculants that float to the surface for removal.

An electrochemical process offers outstanding benefits when compared to other technologies:

  • Can treat both process and waste water
  • Treats a wide range of contaminants
  • Operation uses safe, simple equipment
  • Typically, no need for chemical treatment
  • Can typically reuse electrocoagulation-treated waters, minimizing waste

The electrochemical process is complex, but well understood. It involves three distinct stages that incorporate chemical and physical phenomena.

 


STAGE 1 – ELECTROLYTIC OXIDATION & IN-SITU FORMATION OF COAGULANTS

Electrolytic Oxidation of the sacrificial electrode (typically iron or aluminum) resulting in the formation of:

Oxides

Hydroxides: e.g., aluminum hydroxide (a polymeric hydroxide formed when aluminum hydrolyzes) is an excellent coagulating agent

Oxyhydroxides

STAGE 2 – DESTABILIZATION OF CONTAMINANTS, EMULSIONS, PARTICULATES

Destabilization of contaminants, breaking emulsions, and particulate suspension:

Ions generated by oxidation of the sacrificial electrode interact to compress the diffuse double layer around charged contaminant species.

Ions produced by the electrochemical dissolution of the sacrificial electrode neutralize charges of ionic species present in process and wastewaters and reduce the electrostatic interparticle repulsion.

Reduction of inter-particle repulsion enables van der Waals attraction to dominate, resulting in coagulation.

STAGE 3 – FLOC FORMATION

Aggregation of the destabilized phases and particulates to form floc:

Oxides, hydroxides, and oxyhydroxides provide active surfaces for the adsorption of the contaminating species.

Floc formed as a result of coagulation entraps and bridges colloidal particles remaining in the aqueous medium.

Electrolyzed water produces small bubbles of oxygen at the anode and hydrogen at the cathode. The bubbles attract flocculated particles and float flocculated materials to the surface.

 


DEMONSTRATING THE THREE STAGE ELECTROCOAGULATION PROCESS

STAGE 1
STAGE 2
STAGE 3

 

PASSIVATION – THE CULPRIT

While the complexity of electrocoagulation technology has been understood and proven effective for many years, technical issues and operating costs have restricted its use. Perhaps its largest detractor is passivation.

During the electrocoagulation process, electrodes become coated and fouled with a non-conducting oxide, especially when processing wastewater with high concentrations of dissolved solids and scaling compounds. This passivation causes the electrocoagulation process to fail through reduced efficiency, increased power consumption and time-consuming maintenance necessary to manually clean, acid wash or replace electrode plates.

Water Vision has the answer to eliminating the electrocoagulation water treatment problems associated with passivation. That answer is Thincell. Thincell technology is based on the principles of electrocoagulation but is radically different.

Learn how Thincell successfully capitalizes on the best parts of traditional electrocoagulation, overcomes its obstacles, and offers a radically different and superior technology.

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