Electrocoagulants Characteristics and Application of Electrocoagulation for Micropollutant Removal and Transformation Mechanism

Research summary

Electrocoagulation (EC) is a water-treatment method that uses an electric current to dissolve a sacrificial metal electrode, generating coagulant particles that capture and help remove dissolved contaminants. Much of the process’s effectiveness is thought to depend on the properties of those coagulant particles themselves — their crystal structure, surface area, porosity, and how readily they dissolve — yet this side of the process is less studied than the electrochemistry itself. This study examines how two adjustable parameters, applied current and the electrolyte’s counter-ion, shape the iron-based coagulants produced by Fe electrocoagulation, and then tests how well the resulting coagulants remove three pharmaceutical micropollutants: acetaminophen, antipyrine, and atenolol.

What the study examined

• Crystal phase and surface morphology of iron coagulants generated by Fe electrocoagulation under different applied currents (50-250 mA) and electrolyte counter-ions (chloride, sulfate, carbonate, bicarbonate)
• Surface area and pore structure of the coagulants, measured with BET gas-adsorption analysis
• Removal of three micropollutants — acetaminophen, antipyrine, and atenolol — measured as total organic carbon (TOC) reduction across the different electrolyte and current conditions
• Degradation pathways and intermediate breakdown products of the micropollutants, identified using liquid chromatography-mass spectrometry (LC-MS/MS)

Main findings

Across nearly all tested conditions, the coagulants generated were a mixed-phase iron oxyhydroxide dominated by goethite. Applied current controlled particle shape: currents at or below 100 mA produced flake-like coagulants, while currents of 150 mA and above produced spherical particles. The electrolyte’s counter-ion further shaped particle morphology — chloride and sulfate tended to produce spherical particles, while carbonate and bicarbonate produced nanosheet and nanorod structures — and surface area varied considerably between conditions, from about 143 m2/g down to 42 m2/g as coagulation intensified.

Micropollutant removal tracked closely with these particle characteristics. Coagulants generated in carbonate and bicarbonate electrolytes, which had the largest surface area, pore volume, and pore diameter, achieved the best results: over 90% and 80% TOC reduction, respectively, compared with under 60% for sulfate electrolyte. Mass spectrometry identified around six to seven intermediate breakdown products for each micropollutant, showing that the compounds were progressively broken into smaller molecules through hydroxylation and ring-opening reactions rather than being removed intact.

Why it matters

The results reframe iron electrocoagulation less as a single fixed process and more as something that can be tuned: choosing the applied current and electrolyte composition changes the coagulant’s crystal phase, shape, and surface area, which in turn changes how effectively it removes pharmaceutical pollutants from water. Because the study also mapped how the pollutants actually break down during treatment, rather than only measuring how much disappears, it offers a clearer picture of what happens to contaminants like acetaminophen during electrocoagulation-based water treatment — useful for engineers optimizing EC systems for micropollutant removal.