Preparation of a Highly Selective Fluorine Adsorbent by Mechanochemical Treatment from Ilmenite

Abstract

Fluorine is used in industrial fields such as electronics, glass processing and so on, and has a large impact on human body. The treatment of fluorine-containing wastewater with lower than Japanese effluent standard of fluoride (8 mg/L) is needed. The adsorption method is attracting attention, and titanium hydroxide (Ti(OH)₄) has high adsorption capacity and high selectivity for fluoride ion due to the hydroxy group (Ti-OH) on the surface. However, production of titanium hydroxide requires high energy. In this study, we aim to prepare a highly selective fluorine adsorbent from ilmenite by mechanochemical treatment to remove low-concentration fluorine in wastewater selectively. Fluorine adsorption of the products from ilmenite by mechanochemical treatment increased for 60 min regardless of the ball diameter used in mechanochemical treatment, and fluorine adsorption of the product from ilmenite was 4.5 times higher than that of raw material after 60 min mechanochemical treatment. Fluorine adsorption on product increased to the maximum at pH 2-3, and the product can remove fluoride ion in seawater at pH 2, selectively. The fluorine adsorption behavior followed Langmuir model and Freundlich model, and maximum adsorption amount of fluoride ion by product from ilmenite was 0.050 mmol/g. Regardless of the temperature the adsorption rates of product from ilmenite follow the pseudo-second order kinetic model than the pseudo-first order kinetics model. The adsorption on the product from ilmenite is the endothermic nature of the adsorption process and spontaneous reaction.