Desorption and recovery of fluoride adsorbed by the aluminum-loaded chelating resin

The desorption ability of metal-loaded resins is the key factor limiting the application for fluoride removal.In this study, the desorption behaviors of fluoride adsorbed by an aluminum-loaded chelating resin (D751) were investigated at relatively low liquid/solid ratios.The feasibility of recovering fluoride from the desorption solution was determined by the experiments and the thermodynamic modeling.The results showed that NaOH was a more suitable desorption reagent than HCl.The desorption ratio of fluoride surpassed 80% after 30 min in 2.0 mol/L NaOH.The fluoride concentration of the desorption solution was 2.8-12.8g/L with a F/Al molar ratio of 1.0.The F/Al molar ratio and reaction pH were the main factors determining the recovery of fluoride from the desorption solution.More than 80% of the fluoride was recovered from the desorption solution as cryolite products after the addition of HF and HCl.The residual fluoride concentration decreased from 3,508.2 mg/L to 401.8-482.5 mg/L at a F/Al molar ratio of 5.0-6.0 and at pH 6.0.