Preparation and adsorption performance of anion-doped titanium-based cesium ion sieves

This paper describes the successful construction of a fluorine-doped titanium series cesium ion sieve precursor (CTO-F) with an optimized surface coordination structure. This was achieved by introducing a trace amount of fluorine into the TiO₂ lattice using a modified solvothermal method with regulation control fluoride ion doping. The precursor was then acid-modified to produce fluorine-doped protonated titanate (HTO-F). The addition of fluorine ions was found to significantly enhance the cesium ion trapping ability of the titanium-based cesium ion sieve. The materials CTO-F and HTO-F were characterized post-synthesis via XRD, SEM, EDS, FT-IR, Raman spectroscopy, XPS, BET and TG-DTG to evaluate their structural and compositional properties. This demonstrated that trace fluoride ion doping did not alter the original layered structure of Cs₂Ti₆O₁₃. A series of adsorption experiments were performed to evaluate the influence of solution pH, initial Cs⁺ concentration, and contact time on the adsorption performance of the ion-exchange sieves. Additionally, this paper investigates and discusses the effects of dilute hydrochloric acid concentration on the acid modification of CTO-F, the selectivity of HTO-F for cesium ion in mixed-ion and single-ion solutions, and the stability of HTO-F's adsorption capacity during cyclic experiments. The experimental study showed that HTO-F, after being modified with 0.4 M dilute hydrochloric acid, could reach a saturation adsorption capacity of 373.16 mg/g under optimal conditions of 298 K, pH = 12, and an initial cesium ion concentration of 3000 mg/L. HTO-F exhibited high selectivity and adsorption capacity for Cs⁺ after five adsorption-desorption cycles. After five cycles, its adsorption capacity for Cs⁺ was still 82.7 % of the initial capacity, demonstrating its good cyclic stability.