Comparative Studies on Electro-Membrane Processes for Recovery of Ascorbic Acid from its Sodium Salt

Abstract

This article presents an efficient electro-membrane reactor with three compartments (EMR-3) for in situ ion substitution and recovery of ascorbic acid (ASH) from its sodium salt (ASNa). In situ ion substitution, separation, and recovery of ASH from ASNa were achieved by EMR–3 using the ion-exchange membranes (cation-exchange membranes: CEMs), based on the principle of electro-electrodialysis. Process performances of EMR–3 and electrodialysis (ED) were compared. Under optimum operating conditions for EMR–3 at 3.0 V cm⁻¹ applied voltage (after passage of 3.41 × 10³ Coulombs), current efficiency (CE), and energy consumption (W) were found to be 94.3% and 2.63 kWh kg⁻¹, respectively, corresponding to 95% recovery of ASH. While by ED, under the similar experimental conditions, CE and W were found to be 59.1% and 5.44 kWh kg⁻¹, respectively corresponding to 86.3% recovery of ASH. It was concluded that EMR–3 showed high CE, recovery, and low W, in comparison with ED under similar experimental conditions. Thus the proposed EMR–3 is an efficient alternate for producing ASH from ASNa in an by economical and environmentally-friendly manner. Also, the production of NaOH in cathode stream is a spinoff of EMR–3.

Keywords:

• ascorbic acid
• current efficiency
• electro-membrane reactor
• electrodialysis
• ion-exchange membrane

ACKNOWLEDGEMENTS

The Authors are extremely thankful to the BNRS, DAE, Goverment of India, for providing financial assistance by sanctioning project no. 2007/35/35/BNRS/102. We acknowledge the analytical science division, CSMCRI, Bhavnagar, for instrumental support.

Notes

^a Measured by membrane potential in equilibration in with 0.01 M and 0.1 M NaCl solutions.

^b Measured in equilibration with 0.1 M NaCl solution.

Uncertainty for measurements: 1: 1.0 µm; 2: 0.1%; 3: 0.01 mequiv./g of dry membrane; 4: 0.01; and 5: 0.01 × 10⁻³ S cm⁻¹.