Hardness removal by a novel electrochemical method

• A novel concept of electrochemical method was proposed for hardness removal.
• The synergistic removal rate and the sum removal rate were compared.
• The optimal operating condition was determined by studying influence factors.
• The relationship of different economic parts was established for the novel method.

A novel electrochemical system was proposed to remove hardness species, which has synergistic effect of the conventional electrocoagulation (EC) and electrochemical precipitation (EP). The synergistic removal rate and the sum removal rate of two conventional methods were compared, and the difference value of the two removal rates was used to determine the optimum operating conditions. The results showed that the optimum synergistic effect was obtained when the current density of EC cell was 20 A/m2, the current density of EP cell was 250 A/m2, the consistent flow rate was 120 ml/min, the pH value was 7.2, the water temperature was 60 °C, the recycle time was 130 min, and the initial hardness concentration lower was better. The order must be EC and then EP to have the synergistic effect after comparing the removal rates of different processes. The total cost of the novel system was divided into three parts: Al cost of 11.02%, power cost of 85.33% and DSA cost of 3.65% under the optimum conditions. Then the variations of power cost, Al cost and Dimensionally Stable Anodes (DSA) cost with current density, were analyzed to provide a reference for industrial operators.