Comparative Analysis of Chloride Removal Effect and Reaction Mechanism of Lime-aluminum Method
In this study,the lime-aluminum method was used to treat chloride ions in desulphurization wastewater,and macroporous pseudo-boehmite and sodium meta-aluminate were used as aluminum salts,and the effects of the conditions such as reaction time,dosage of chemicals,and reaction temperature on the efficiency of chloride removal,as well as the mechanisms of the two aluminum salts were comparatively analyzed.The results show that the reaction temperature plays a decisive role in the reaction.When the reaction temperature is about 55℃,under the dual effects of the alkaline environment generated by the dissolution of calcium oxide and the reaction temperature,the hydrolysis of macroporous pseudo-boehmite produces hydroxyl(-OH)to form Al(OH)4-,and combines with Ca2+to remove Cl-,and the reaction precipitates mainly consist of Ca4Al2O6Cl2-·10H2O and Ca(OH)2,and the Cl-removal rate is about 55.9%.The suitable temperature range for sodium meta-aluminate is 30℃～40℃,and the maximum Cl-removal rate can reach 57.9%,and the reaction speed is faster than that of macroporous pseudo-boehmite.Sodium meta-aluminate is rapidly hydrolyzed to produce Al(OH)4-in the system of chloride removal,while calcium oxide is dissolved and reprecipitated,and both of them rapidly capture the Cl-in the reaction system,and the reaction precipitates are mainly Ca4Al2H0.36O6.34Cl1.67,Ca4Al2O6Cl2·10H2O,Ca2Al(OH)7·3H2O and Ca(OH)2.
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