Synthesis Conditions and Sorption Mechanism of F− Sorbents Utilizing Seashells

Abstract

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-.

Keywords

• fluoride ion
• seashells
• sorbent
• fluorapatite
• waste utilization