Separation of sodium sulfate from high-salt wastewater of lead-acid batteries

• Published in: Chemical engineering research & design 2021-12, Vol.176, p.194-201
• Main Authors: Liu, Xin, Zhang, Zhengmin, Zhang, Lin, Bu, Shi, Xu, Weigang, Shi, Chengcheng, Fang, Jiamei, Xu, Chen
• Format: Article
• Language: English
• Subjects: Batteries; Chloride ions; Crystallization; Evaporation; Evaporation crystallization; High-salt waste water; Ion concentration; Lead acid batteries; Membrane separation; Purity; Salt; Salt separation; Separation; Sodium; Sodium chloride; Sodium sulfate; Wastewater
• ISSN: 0263-8762; 1744-3563
• DOI: 10.1016/j.cherd.2021.10.008

[Display omitted] •The effect of concentration ratio on precipitation amount and purity was revealed.•The optimal temperature for the separation and purification of Na2SO4 was obtained.•The optimal concentration ratio of the separated and purified Na2SO4 was obtained.•The experimental data are fitted with the mathematical model. Salt separation experiments are selectively conducted for the high-salt wastewater of lead-acid batteries. Two useful products, sodium sulfate and sodium chloride, are obtained by evaporation crystallization. The experiment investigates the effect of different temperatures and concentration ratios on the precipitation content and purity of sodium sulfate and sodium chloride during the evaporation and concentration of wastewater, and explores the optimal concentration ratio and temperature for the separation and purification of sodium sulfate. Moreover, the experimental data are fitted with the mathematical model. The results show that for wastewater with 0.5 L chloride ion concentration of 17.9 g/L and sulfate ion concentration of 188.4 g/L, sodium sulfate with 98% purity can be obtained when the concentration ratio is 1.66. When the concentration ratio is in the range of 1.66–2, the precipitation of sodium sulfate is more than 25.76 g in the range of 50 °C–90 °C. When the evaporation temperature is stable at 60 °C and the concentration ratio is from 1.46 to 3.5, both the yield and purity of sodium sulfate crystals are improved, the precipitation of sodium sulfate is up to 88.63 g and the purity is up to 98%.