Journal du génie chimique et de la technologie des procédés
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A Continuous Directional Solvent Extraction Desalination Process Realized with the Aid of Electro-coalescence

Shirui Luo, Yunsong Pang and Tengfei Luo

The recently demonstrated non-membrane, low-temperature directional solvent extraction (DSE) is promising to
reduce desalination cost by eliminating the need of membranes and utilizing low-temperature energy sources from
solar energy or waste heat. This paper investigates the technical feasibility of a continuous DSE water desalination
process using decanoic and octanoic acid as directional solvents (DS). A continuous lab-scale DSE prototype is
realized with the aid of electro-coalescence (EC) with a capacity of producing 28 ml/h of freshwater. A preliminary
economic analysis shows that the operational cost of DSE desalination is estimated to be ~$3.03/m3. Our results
reveal two critical technological aspects that need further research to push DSE closer to deployment. These include
(1) identifying more effective DSs with higher water yield; (2) optimizing the EC to improve the separation efficiency
and effectiveness. Both aspects will be critical to increase water production rate and decrease energy cost of DSE
desalination. Our cost analysis indicates that the desalination cost of DSE can reach ~$0.25/m3, if the DS
performance can be improved by four-folds and the EC efficiency is increased to 90%. In summary, the current work
lays a framework upon which further research on the continuous DSE desalination process can be based. Once it is
mature and widely deployed, DSE is promising to lower the desalination cost by utilizing low-temperature waste
heat, which will contribute significantly to ameliorating the global water scarcity problem.