China Nonferrous Metallurgy

As an important ore for extracting lithium, lepidolite will produce a large amount of fluorine-containing wastewater and leaching residue in the smelting process, which will cause serious pollution to the environment. In this paper, the lemica leaching residue was used as the basic skeleton and modified by high-temperature roasting and aluminum sulfate solution soaking to prepare a new type of defluorination material. The morphology and structure of the modified material were analyzed by SEM, TEM, XRD and FTIR, and its defluorination performance was studied by static adsorption experiment. The adsorption mechanism was studied by adsorption kinetics and isothermal adsorption line model. The results show that the modification does not remove fluorine from the leucite residue, and greatly changes the surface morphology and increases the number of active sites on the surface. Under the conditions of roasting temperature 450℃, roasting time 2h, concentration of aluminum sulfate solution (Al³⁺) 12g/L, dosage of adsorbent 5g/L, reaction temperature 25℃, initial concentration of fluorine-containing solution 5mg/L, and so on, the RAA adsorbent prepared by roasting-aluminum sulfate solution soaking-alkali modification was prepared for 1min. The defluorination rate reached 91.56%, the adsorption equilibrium was reached in 180min, and the final defluorination rate was up to 95.12%. The adsorption process was highly fit with Langmuir model and quasi-second-order kinetic model, that is, single-molecular layer adsorption and chemisorption were the main processes. The modified lemica leaching residue shows good adsorption capacity for fluorine in water and can effectively remove fluorine pollution, and the fluorine in the slag will not be removed during the modification process, so it can be applied to the treatment of other high fluorine groundwater.