Study on the process and mechanism of chloride ion adsorption by ultra-high lime aluminum method.

The ultra-high lime aluminum method (UHLA) is a method that can effectively adsorb chloride ions in a solution. Calcium oxide (CaO) and sodium aluminate (NaAlO₂) were mixed and added to the sodium chloride solution. After the reaction lasted for some time, the content of chloride ions in the solution was significantly reduced. Through the experiment of chloride ion adsorption, it was found that when the mass ratio of calcium oxide to sodium aluminate was m(NaAlO₂):m(CaO) = 1:2.5, the reaction temperature was 25°C, and the stirring time was 60 min, the adsorption effect on chloride ion was the best. The adsorption rate can reach 93.3% in a 100 mg/L sodium chloride solution. With the increased sodium chloride concentration, the time required to reach adsorption equilibrium becomes longer. In a 2,000 mg/L sodium chloride solution, this method's unit adsorption mass of chloride ion can reach 63.5 mg/g. Through SEM and XRD analysis, calcium oxide and sodium aluminate react in solution to form Ca₄Al₂(OH)₁₄ with a layered structure. The OH- between the layers can exchange with external chloride ions. After Ca₄Al₂(OH)₁₄ adsorbs chloride ions, the product is Friedel's salt (Ca₄Al₂Cl₂(OH)₁₂) with the same layered structure. [ABSTRACT FROM AUTHOR]