REMOVAL OF CAUSTIC SODA FROM INDUSTRIAL WASTEWATER

Abstract

Sodium hydroxide is commonly used as a strong base by various chemical industries. The processed wastewater therefore enhances the pH levels of the receiving water bodies affecting the physiological functions of aquatic organism, plant and makes the water inappropriate for consumption. In this study, two stage electrodialysis process, for removal of NaOH from industrial wastewater was investigated. 1.0 μm PTFE (Advantec, USA), Forward Osmosis (FO) (Hydration Technology Innovation) membranes, platinum coated over titanium anode, and graphite cathode were used. In the first stage, synthetic NaOH wastewater was diffused through PTFE membrane. In the second stage, electrodialysis was performed, in which ions are transported from one solution to the other under the influence of applied electric potential. During diffusion, the transfer rate of caustic soda, from feed solution having concentration 1.0 Molar to 3.0 Molar of NaOH, to draw solution was observed up to 62% in 12 hours. Removal of caustic soda was observed within the range 60 - 83% from feed solution to draw solution, if draw solution was replaced after 12 hours with DI water. Draw solution of the process was then transferred to the electrodialysis cell as feed solution. During electrodialysis process, up to 44 % NaOH recovery was observed.