Influence of external electric field on polymerization of Fe (III) flocculant in water: A reactive molecular dynamics and experiment study

•EEF enhances the chemical bond between Fe3+ and OH–(hydroxyl bridge).•EEF increases forming [Fe2(OH)2(H2O)8]4+, further tend to form larger particles.•EEF makes particles in water more active and easier to collide and aggregate. In the present study, a novel method of electrochemically enhancing hydrolysis of Fe (III) was proposed. The influence of an external electric field (EEF) on initial polymerization of Fe(III) was investigated by using reactive MD simulation method. It is examined in term of the structural property (radial distribution function), bond order, electrostatic energy, polymerization products, and kinetic characteristic (self-diffusion coefficient) in the hydrolysis system. Then an experimental study was carried out to verify the MD simulation conclusions. The results show that EEF can shorten the distance between Fe3+ ions, enhance the bonding strength between Fe3+ ions, enhance the activity of particles, thus promote the formation of dimer [Fe2(OH)2(H2O)8]4+, and further produce particles with larger size and surface area, which is beneficial to enhance the ability of particles to adsorb impurities. Then the experimental results of particle size distribution of FeCl3 flocculating particles and the Zeta potential of the FeCl3 solution under different EEF meet well with the MD simulation conclusions. The method of electrochemically enhancing hydrolysis proposed in this paper is expected to effectively improve the flocculation performance of ferric chloride, and then reduce the dosage of ferric chloride in practical application.