Regeneration of sodium bicarbonate from industrial Na-based desulfurization waste using ammonium hydroxide

In an effort to improve industrial waste recycling and realize zero-waste technology, we optimized the regeneration of sodium bicarbonate from desulfurization waste using aqueous ammonia. Sodium bicarbonate is essential for absorbing SO2 gas in flue gas desulfurization. Based on X-ray fluorescence analysis, desulfurization waste consists of 86.2% sodium sulfate. Rapid deposition of undesired ammonium bicarbonate in a reactor was observed at the early stages of the reaction when using ammonia gas, resulting in insufficient yield. For further improvement, the effect of ammonia solution dosage was explored in detail. The yield/purity of sodium bicarbonate regenerated from desulfurization waste is very close to that from pure sodium sulfate, 58.2/85.9% and 56.6/91.5%, respectively. Moreover, owing to greater surface area, the as-regenerated sample showed higher desulfurization performance (97% removal rate) than commercial sodium bicarbonate (88.6%) on 200 ppm SO2 gas at a 5 g/min feeding rate.