Process optimization to enhance utilization efficiency of precipitants for chloride removal from flue gas desulfurization wastewater via Friedel's salt precipitation. (1st December 2021)

• Record Type: Journal Article
• Authors: Ye, Xiaofang; Zhao, Xiaodan; Ming, Qiang; Zhu, Jun; Guo, Jiaming; Sun, Dongqi; Zhang, Sheng; Xu, Jie; Zhou, Zhen
• Is Part Of: Journal of environmental management. Volume 299(2021)
• Publication Date: 2021-12-01
• Subjects: Chloride removal -- Friedel's salt -- Flue gas desulfurization wastewater -- Utilization efficiency; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2021.113682
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: The treatment cost for Cl − removal by Friedel's salt precipitation depended significantly on utilization rate of the precipitant aluminate. In this study, effects of Ca/Al molar ratio, reaction time, temperature and Al/Cl molar ratio were investigated to maximize Al utilization rate for Cl − removal from flue gas desulfurization wastewater. Batch results showed that the maximum Al utilization rate of 55.8–60.3% was obtained at Ca/Al ratio of 3.00, reaction time of 90 min, temperature of 35 °C and Al/Cl ratio of 0.50 regardless of the initial Cl − concentration. The precipitate obtained at the highest Al utilization rate had the highest interlayer spacing, the best crystal integrity, and the strongest binding energy of the Al–OH bond. The optimized condition made ion exchange between Cl − and OH − easier, and obtained more stable Friedel's salt structure to adsorb Cl − . Pilot-scale results showed that maximizing Al utilization rate with low dosages of precipitants had insignificant effects on the removal of Mg 2+, Ca 2+ and sulfate compared to the strategy to maximize Cl −, but enhanced Al utilization rate from 38.2% to 56.4%. Economic analysis showed that enhancing Al utilization rate greatly reduced treatment cost of the Friedel's salt precipitation method by 30.5%, and made the two-stage desalination process more feasible and worth popularizing. Graphical abstract: Image 1 Highlights: Aluminate (Al) utilization rate was maximized for Cl − removal by Friedel's salt (FS). Al utilization rate was enhanced from 20 - 40% to 55.8–60.3% after optimization. Optimization increased FS crystal integrity and binding energy of Al–OH bond. Pilot-scale test confirmed stability of hardness and Cl − removal after optimization. Enhancing Al utilization rate reduced treatment cost of FS precipitation by 30.5%.