Removal of High-Concentration Sulfate Ions from the Sodium Alkali FGD Wastewater Using Ettringite Precipitation Method: Factor Assessment, Feasibility, and Prospect

Abstract

e 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 NaAlO 2 dosage, Ca(OH) 2 dosage, solution temperature, anions (Cl − , NO 3 − and F − ), and heavy metal ions (Mg 2+ and Mn 2+ ), 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 SO 4 2− 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 NO 3 − also can be removed minimally by the method. e result of actual wastewater treatment shows that the method is feasible for treating high-concentration sulfate wastewater. e ettringite precipitation method has the potential to be a commercial application in the future.

Thermodynamic Simulations for Determining the Recycling Path of a Spent Lead-Acid Battery Electrolyte Sample with Ca(OH)2

“…Therefore, ambient CO2 should be avoided in the precipitation process to obtain a higher removal efficiency. Also, the theoretical results obtained in this model are very close to the experimental results of Fang et al [23]. 4c) and SO 4 2− (Figure 4b), according to Equation (11).…”

“…Due to the high concentrations of SO 4 2− in the spent electrolytes, chemical precipitation was adopted. BaCl 2 [22], limestone [19], and ettringite [23] have been used to remove SO 4 2− in wastewater, while no detailed theoretical calculation has been reported.…”

Over-sulfated soils and sediments treatment: A brief discussion on performance disparities of biological and non-biological methods throughout the literature

“…Chemical background ranged from hyper alkaline to highly acid configurations, which were not necessarily suited for the expected stabilizing minerals. As previously mentioned, SO 4 2- removal through ettringitic processes requires specific pH ranges (Dou et al, 2017; Fang et al, 2018).…”

“…Conversely, high alkalinities allow perennial precipitation of ettringite, and are thus used for urban wastewaters (Dou et al, 2017; Fang et al, 2018) and mine water cleaning purposes. Therein, Madzivire et al (2010) used fly ash (FA) as a low-cost Al source for the treatment of mining effluents.…”

“…Fang et al (2018) tested the influence of reagents dosage (NaAlO 2; Ca (OH) 2 ), temperature variations, competing anions (Cl - , NO 3- , F - ) and metallic elements (Mn 2+ , Mg 2+ ) on SO 4 2- removal. Temperature had the most remarkable effect, as removal rates decreased from 99% under the most propitious temperature (25°C) to 36% for the most disfavouring condition (80°C).…”