Spatially decoupled electrochemical strategy for lime passivation prevention and sustainable phosphate recovery

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Abstract
Lime-based precipitation, though widely adopted for wastewater phosphorus (P) removal, suffers from surface passivation. The passivation layer inhibits Ca2+ release, forcing excessive dosing while yielding low-quality sludge and effluent with elevated hardness and pH. Limestone, despite its economic and environmental benefits, exhibits limited efficacy under fluctuating alkalinity. Here, we develop a limestone-integrated electrochemical system that spatially decouples the dissolution and precipitation reactions. By strategically positioning limestone at the acidic anode, we ensure sustained Ca2+ release without passivation, while cathodic alkalinity enables efficient P recovery (85.7%). The system produces high-purity products (15.2 wt% P) at low energy consumption (14.8 kWh kg P-1) and delivers superior effluent quality. Beyond its robustness and capacity flexibility over long-term operation, the electrochemical strategy reduces overall costs by 73.2% and carbon emissions by 29.1%, positioning it as a cost-effective and sustainable alternative to traditional lime-based wastewater treatment with remarkable passivation resistance and resource recovery efficiency.
Funding Information
  • Shenzhen Science and Technology Innovation Commission (JCYJ20230807093405011)
  • Shenzhen Science and Technology Innovation Commission (JCYJ20250604144607011)
  • Natural Science Foundation of Guangdong Province (2023A1515110152)

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