Recovery of baking soda from reverse osmosis reject of desalination plant using carbon dioxide gas

Abstract

The extraction of baking soda from the reverse osmosis (RO) reject of desalination plant using CO₂ gas has been studied. The novel idea of using amino acid additives to improvise the conventional Solvay process and thereby increasing the Na⁺ recovery efficiency has been explored. Three amino acid additives namely Glycine, L-Arginine and L-Alanine are studied for their effect on increasing Na⁺ recovery and the best suitable additive is selected. Necessary parameters governing the recovery such as concentration of amino acid, reaction temperature, flowrate of CO₂ and carbonation time have been optimized with a view to get a maximum recovery efficiency by the modified Solvay process. Under the optimized conditions maximum sodium recovery of 70% is obtained. The modified Solvay process has yielded a higher recovery efficiency compared to the conventional Solvay process (33%). Amino acid additive (alanine) has increased the conversion efficiency and has also helped in reducing the ammonia requirement of the process. The results obtained show a feasible way to protect our environment by utilizing the reject of the desalination plant and the industrial waste gas carbon dioxide in bicarbonate production.