Fluoride(F^-) is present in wastewater produced by various industries, such as semiconductor, glass processing, mining and smelting. Development of high-efficient and low-cost treatment processes of wastewater is desirable. In this study, Seashells sorbents for F^- removal were synthesized by phosphate solution treatment of seashells (oyster, scallop, sea urchin and barnacle) waste at room temperature. The seashells sorbents could remove F^- in water to below effluent standard (8 mg/L) in Japan. The optimal initial pH range for seashells sorbents synthesis was below pH6. The phosphate consumptions for synthesis could be estimated by specific surface area of seashells. F^- sorption isotherms of seashells sorbents were fitted well by the Langmuir model. The synthesis reaction of seashell sorbents at room temperature was that calcium hydrogen phosphate was produced to the surface of calcium carbonate contained in seashells. Dominant mechanism of F^- removal of seashell sorption was identified as to form fluorapatite from the calcium hydrogen phosphate and F^-.

Scandium (Sc) has no commercially viable independent deposits and is mainly recovered as a by-product of the smelting of other ores. In the process of recovering nickel from laterite ores, Sc is recovered from sulfuric acid leachates. An ion-exchange resin method is an effective way to recover low concentrations of Sc(III) in sulfuric acid leachates. In addition to Sc(III), the leachates also contain trivalent metal ions Cr(III), Al(III), and Fe(III). This study proposes optimal adsorption conditions for the selective separation and recovery of Sc from other trivalent cations in sulfuric acid solutions using CR11. The adsorption behaviors of the trivalent ions Sc(III), Cr(III), Al(III) and Fe(III) were thermodynamically investigated. With increasing temperature, the equilibrium adsorption amounts of Cr(III) and Al(III) increased, that of Fe(III) decreased below 10 mmol L^-1 and increased above 10 mmol L^-1, while that of Sc(III) changed little. The adsorption data were measured and fitted by three models, namely, the Langmuir, Freundlich, and Langmuir-Freundlich models. The values of the coefficient of determination (R²) show that the Langmuir-Freundlich model is more suitable than the other models. The co-adsorption with SO₄^2- anions after 0.4 - 0.8 mmol g-1 adsorption of trivalent cations may be one reason for the fit to the Langmuir-Freundlich model. In this study, column tests with synthetic solutions were also investigated. Apparent distribution coefficients of metal ions and apparent separation factors of Sc(III) versus other metals were defined as indicators of the optimal solution volume to be fed for scandium recovery.