Synergistic scale inhibition mechanisms in electrochemical water softening coupled with temperature-responsive star-shaped inhibitors

Synergistic scale inhibition integrating electrochemical water softening (EWS) with scale inhibitors is proposed as a process-intensified strategy to mitigate scaling and enable higher cycles of concentration (CoC) in circulating cooling water systems. Distinct from conventional linear UCST-type polymers, the star-shaped topology introduces a confined internal architecture and elevated local functional group density, which strengthen cooperative intramolecular hydrogen bonding and enable a sharper and more controllable upper critical solution temperature (UCST) transition. A temperature-responsive star-shaped polymer scale inhibitor (star-SI) was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization and exhibits reversible conformation contraction–expansion behavior. At high temperatures, the scale inhibition performance of star-SI remains unaffected by the electric field and electrode reactions, achieving an inhibition efficiency exceeding 95%. At low temperatures, star-SI does not interfere with cathodic precipitation in EWS, yielding a CaCO 3 precipitation rate of up to 16.05 g/(m 2 ·h) at 36 A·m −2 . Molecular simulations and electrochemical analyses indicate that star-SI adopts a contracted conformation at low temperatures and exhibits negatively charged characteristics near the cathode and alkaline interfaces, thereby minimizing interference with electrochemical softening. Additionally, star-SI adsorbs onto the surface of CaCO 3 crystals, modulating growth kinetics and delaying nucleation at the heating interface. This synergistic system enables a novel treatment mode of room-temperature hardness removal and high-temperature scale inhibition.