Selective electrochemical separation and recovery of calcium and magnesium from brine

Desalination via reverse osmosis (RO) generates a stream of fresh water and an almost equivalent volume of highly concentrated brine as waste. The waste brine is usually disposed back to the sea which increases the sea salinity in a way that can affect the marine life. Treatment of this waste brine is vital for the environment. The treatment process can be made feasible by extracting value added products from this waste brine. In this context, the current study demonstrates a novel two-step electrochemical process for selective separation and recovery of calcium and magnesium from brine. The first step involves purging carbon dioxide in the brine solution while electrochemically precipitating calcite using titania coated graphite cathode and pristine graphite anode at an applied potential of 2.5 V. The use of titania coated surface was found to be effective in promoting selective calcite precipitation. After calcite removal, brucite is selectively precipitated using pristine graphite cathode and anode at an applied potential of 3.5 V. This study also reveals the importance of DC potential and the electrode material for selective precipitation of calcium and magnesium ions from brine. Ion chromatography was used to analyze the concentration of calcium and magnesium ions in the treated and non-treated brine. X-ray diffraction and scanning electron microscopy of electrode precipitates confirmed the removal of calcium and magnesium from brine as calcite and brucite, respectively. Besides reducing the brine salinity, the developed process yields two separate compounds which can be further converted into calcium and magnesium-based products for several commercial applications.

Automated summary

Novel electrochemical process demonstrated selective separation and recovery of calcium and magnesium from brine, highlighting importance for environmental protection and resource utilization.