Efficient and green water softening by integrating electrochemically accelerated precipitation and microfiltration with membrane cleaning by periodically anodic polarization

Anode Boundary Layer Extraction Strategy for H+–OH– Separation in Undivided Electrolytic Cell: Modeling, Electrochemical Analysis, and Water Softening Application

“…Although the long-term stability of a Ti tubular anode for boundary layer abstraction might suffer from pore clogging by finely dispersed particles and suspended matters, this clogging phenomenon can be effectively solved by employing the conventional backwashing strategy to restore the water flux of a porous Ti tubular anode. Simultaneously, in softening applications, the fouling caused by filter cake accumulation on the filter surface can be effortlessly solved by periodically applying a positive potential on the Ti filter. , As for the fouling on the cathode after a long-term operation process, the strategies such as pickling, ultrasonic cleaning, and mechanical scraping may be required to maintain the electrochemical water softening process. Moreover, the cylindrical geometry of the present electrolytic cell has a higher surface-to-volume ratio, which is favorable in terms of the volumetric power density and industrial scalability.…”

“…Simultaneously, in softening applications, the fouling caused by filter cake accumulation on the filter surface can be effortlessly solved by periodically applying a positive potential on the Ti filter. 52,53 As for the fouling on the cathode after a long-term operation process, the strategies such as pickling, ultrasonic cleaning, and mechanical scraping may be required to maintain the electrochemical water softening process. Moreover, the cylindrical geometry of the present electrolytic cell has a higher surface-to-volume ratio, which is favorable in terms of the volumetric power density and industrial scalability.…”

Research Progress on Novel Electrochemical Descaling Technology for Enhanced Hardness Ion Removal

“…Therefore, a non-selective, porous, and robust separation material can serve as an alternative separator in electrolytic cells. Liu et al [55] found that when using a hydrophilic PTFE membrane as the separator, ions such as Ca 2+ , Mg 2+ , H + , HCO 3 − , CO 3 2− , and OH − could easily pass through the PTFE membrane, maintaining electrical neutrality in the anode and cathode chambers. As the current density increased from 20 A/m 2 to 100 A/m 2 , the scale precipitation rate increased from 97.5 to 348.8 g/h/m 2 CaCO 3 , and the specific energy consumption rose from 0.68 to 1.88 kWh/kg CaCO 3 .…”

“…Therefore, microfiltration, with its small footprint, ease to operation, and manageability, is an effective method for solid-liquid separation, offering extensive surface area for CaCO 3 nucleation and growth, which enhances crystallization and descaling efficiency. Liu et al [55] developed an electrochemical accelerated precipitation softening-microfiltration (EAPS-MF) system for the removal of Ca 2+ hardness from solutions (Figure 4c). In this process, an electrolytic cell is divided by a polytetrafluoroethylene membrane, with alkaline effluent directly entering the crystallizer to form CaCO 3 crystals, which are then intercepted by a titanium pipe microfilter.…”

The three-dimensional arrangement of the cathode weakens the bubble aggregation during the electrochemical water softening reaction

“…Electrochemical descaling technology is a descaling method that emerged in the late 20th century. The principle is to create an alkaline area near the cathode, which promotes the combination of , OH -, Ca 2+ , and Mg 2+ in the water to form a scale layer 9,10 . After treatment, the amount of Ca 2+ and Mg 2+ in the water is effectively reduced, reducing the possibility of scale formation on the equipment surface.…”