Study On Removal Of Heavy Metals Ions And Chloride Ions From Desulfurization Wastewater By Modified Fly Ash-Hydrolite

Reuse and emission reduction of wastewater from coal-fired power plants have significant economic and environmental benefits,especially zero-emission technology will be an important trend for future development.As a by-product of coal burning in thermal power plants,fly ash is a promising low-cost adsorbent that can be used to remove various pollutants.Using fly ash to treat desulfurization wastewater can achieve the effect‘waste to treat waste’.In this study,two adsorbents of fly ash and hydrotalcite were combined and modified with chemical reagents.After high-temperature roasting or microwave irradiation,new adsorbents were screened to remove chlorine ions and heavy metal ions from desulfurization wastewater.The experimental results show that when fly ash and hydrotalcite were combined in a ratio of 2:1,the modified fly ash-hydrotalcite,prepared by using sodium hydroxide as a chemical modifier in combination with a muffle furnace at 450℃for 180 min,had the best adsorption performance for chloride and heavy metal ions.Then,the factors influencing the adsorption performance of modified fly ash-hydrotalcite were investigated experimentally.The results show that the removal effect of Cl^-was the best when p H was 8,the removal efficiency of Cd²⁺and Hg²⁺was the highest when p H was6..When the adsorption temperature was 50℃,the removal rate of Cl^-was the highest,low temperature was beneficial for the removal of Cd²⁺,the removal rate of Cd²⁺was the highest at 30℃,and the removal rate of Hg²⁺was the highest at40℃.When the adsorption time was 180 min,the adsorption process of adsorbent to chloride ions and heavy metal ions basically reached the adsorption equilibrium.Finally,the adsorption capacity of modified fly ash-hydrotalcite for different concentrations of chloride and heavy metal ions was measured at room temperature.By plotting adsorption isotherms,linear fitting and analysis with Freundlich and Langmuir models,it was found that the Langmuir adsorption isotherm model can better describe the adsorption mechanism of chloride and heavy metal ions by modified fly ash-hydrotalcite.