SEPARATION OF GLUCONATE WITH CONVENTIONAL AND BIPOLAR ELECTRODIALYSIS

Gluconate, predominantly produced by fermentation, is widely used in t he form of sodium gluconate, gluconic acid or glucono-delta-lactone as a bulk chemical. Because of undesirable by-products, the conventional isolation and purification method (mainly ion exchange) is problemati c, especially when gluconic acid is generated. In this paper the basic behaviour of the recovery of gluconate using electrodialysis as well as electrodialysis with bipolar membranes is described. Mass transfers and conversion rates are measured depending on gluconate concentratio n or current density. A typical flux was around 2.0 x 10(-4) kg/m(2)s. In addition, current efficiencies, which influence specific energy co nsumption, were considered. Around 3.0 x 10(6) J energy (excluding pum ping) was necessary to isolate 1 kg gluconate. The achievable maximum concentrations, which mainly depend on the ratio between mass transfer of gluconate and water transport, were estimated at approximately 30% (w/v) for the conventional and around 45% in case of the bipolar proc ess.