Investigation on Strontium Adsorption Selectivity of Hydrothermally Synthesized Layered Sodium Titanates

Two layered sodium titanate phases, sodium nonatitanate (Na4Ti9O20) and sodium trititanate (Na2Ti3O7), have been hydrothermally synthesized and their Sr2+ adsorption selectivity was investigated in the coexistence of Cs+ with ionic equivalent concentration. Although both phases exhibit Sr2+ selective adsorption, Na4Ti9O20 adsorbed both Sr2+ and Cs+, while the adsorption of Cs+ was not detected on Na2Ti3O7, despite its higher adsorption capacity. To investigate the causes for the high Sr2+ selectivity of Na2Ti3O7, additional adsorption tests were carried out in different pH, which can be interpreted as the Sr2+ –H+ binary system, and in single and ternary systems of Al3+, Sr2+ and K+ with ionic equivalent concentrations. When changing the pH, the adsorption amount of Sr2+ showed a high and nearly constant value at pH above 4 and drastically decreased at pH below 3, reaching nearly zero at pH 2. In the Al3+–Sr2+ –K+ ternary system, the adsorption amount decreased in the order of Sr2+, Al3+ and K+. The adsorption amount of K+ was low compared to that of Sr2+ and Al3+ in both the single and ternary systems. Meanwhile, the adsorption amount of Sr2+ significantly decreased compared to that in the single system, unlike in the Sr2+–Cs+ binary system where the adsorption of Sr2+ was almost the same. From these results, the high Sr2+ selectivity of Na2Ti3O7 in the Sr2+–Cs+ binary system was anticipated to be due to the size effect. The smaller interlayer spacing of Na2Ti3O7 compared to that of Na4Ti9O20 appears to inhibit the intercalation of Cs+ due to its large ionic radius.

Optimization of nonatitanate electrodes for sodium-ion batteries

NaTi3O6(OH)·2H2O, also known as “sodium nonatitanate” (NNT) can undergo reversible sodium (de)insertion at low potentials centered around 0.3 V.

Sodium Nonatitanate for Removal Radioactive Strontium From Aqueous Contaminated Effluent

Sodium titanate materials which have a layered structure consisting of titanate layers and exchangeable sodium ions are promising inorganic ionic exchangers for strontium adsorption from aqueous solution. The materials used in this study include samples synthesized in a hydrothermal method at different temperatures between 60°C and 200°C. Batch kinetics experiments for strontium removal from aqueous solution were performed. Kinetics data were fitted by using a pseudo second order reaction model and a diffusive model. It was shown that the sorption process occurs in one or two diffusion-controlled steps that depend on the synthesis temperature. The strontium extraction capacity depends on the synthesis temperature with a maximum for sample synthesis at 100°C. This sample has good properties of decontamination at laboratory scale.