Separation and concentration of lactic acid by electro-electrodialysis

Reactive extraction combined with a modified two-phase electro-electrodialysis (MTPEED) process shows a strong potential in the recovery and concentration of lactic acid without generating a salt waste. In this paper, an electro-electrodialysis (EED) process was designed with mixed lactic acid and sodium lactate aqueous solution as catholyte to simulate this MTPEED process. The immediate factors affecting the current efficiency, cell voltage and energy consumption were investigated. The optimization of operating conditions was also discussed. The lowest cell voltage was reached when the sodium lactate concentration was about 1.7 mol L-1. The current efficiency was kept near 100% before lactic acid in the catholyte was exhausted. When the current density was 160.7 A m(-2), a representative specific energy consumption of the MTPEED process was 1.404 kWh/kg lactic acid, far lower than 2.961 kWh/kg lactic acid of a comparable EED process with sodium lactate aqueous solution as catholyte. The cell voltage of the MTPEED process was also affected by the phase ratio of the organic phase to the water phase. The lower phase ratio is preferred. (c) 2007 Elsevier B.V. All rights reserved.