Abstract
The feasibility of removal of sulfate ions from the sodium alkali FGD wastewater using the ettringite precipitation method was evaluated. Factors affecting the removal of sulfate ions, such as NaAlO2 dosage, Ca(OH)2 dosage, solution temperature, anions (Cl−, NO3− and F−), and heavy metal ions (Mg2+ and Mn2+), were investigated, and the optimal experimental conditions for the removal of sulfate ions were determined. Experimental results indicate that the ettringite precipitation method can effectively remove SO42− with removal efficiency of more than 98%. All the investigated factors have influences on the removal of sulfate ions, and among them, the dosage of reagents, solution temperature, and fluoride ions have the strongest influence. In addition, the method can effectively synergistically remove F− and heavy metal ions with removal efficiencies of more than 90% and 99%, respectively; meanwhile, Cl− and NO3− also can be removed minimally by the method. The result of actual wastewater treatment shows that the method is feasible for treating high-concentration sulfate wastewater. The ettringite precipitation method has the potential to be a commercial application in the future.
Highlights
At present, the wet flue gas desulfurization (WFGD) is the most commonly used technology in the field of industrial flue gas desulfurization in China [1]
In order to meet the discharge standard or achieve the recycling of Journal of Chemistry desulfurization wastewater, it is necessary to remove the sulfate ion in the sodium alkali FGD wastewater. Several technologies, such as biological treatment [7, 8], membrane filtration [9], adsorption [10], ion exchange [11, 12], electrocoagulation [13], crystallization [14, 15], and chemical precipitation [16], have been developed to treat sulfate in water. These methods are not very suitable for the treatment of high concentration of SO42− wastewater, except the chemical precipitation method. e chemical precipitation method mainly includes lime precipitation [6], barium chloride precipitation [17, 18], and ettringite (Ca6Al2(OH)12(SO4)3· 26H2O) precipitation methods [19]. e limestone precipitation method is widely used in the field of water treatment; due to the relatively high solubility of gypsum [19], the SO42− removal efficiency is low. e barium chloride precipitation method can reach high SO42− removal efficiency, but a large number of corrosive chloride ions and toxic barium ions will be introduced into the water; besides, barium chloride is more expensive than lime, so the technology is rarely used in the field of flue gas desulfurization wastewater treatment
Previous researches have shown that SO42− removal was signi cantly a ected by NaAlO2 dosage and Ca(OH)2 dosage [21, 22]
Summary
The wet flue gas desulfurization (WFGD) is the most commonly used technology in the field of industrial flue gas desulfurization in China [1]. In order to meet the discharge standard or achieve the recycling of Journal of Chemistry desulfurization wastewater, it is necessary to remove the sulfate ion in the sodium alkali FGD wastewater Several technologies, such as biological treatment [7, 8], membrane filtration [9], adsorption [10], ion exchange [11, 12], electrocoagulation [13], crystallization [14, 15], and chemical precipitation [16], have been developed to treat sulfate in water. E barium chloride precipitation method can reach high SO42− removal efficiency, but a large number of corrosive chloride ions and toxic barium ions will be introduced into the water; besides, barium chloride is more expensive than lime, so the technology is rarely used in the field of flue gas desulfurization wastewater treatment. The optimal experimental conditions for the removal of high-concentration sulfate ions were determined
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