Effect of the synthesis temperature of sodium nonatitanate on batch kinetics of strontium-ion adsorption from aqueous solution

Abstract

Sodium titanate materials are promising inorganic ion exchangers for the adsorption of strontium from aqueous solutions. Sodium nonatitanate exhibits a layered structure consisting of titanate layers and exchangeable sodium ions between the layers. The materials used in this study include samples synthesized by a hydrothermal method at temperatures between 60°C and 200°C. Their structure, composition, and morphology were investigated with X-Ray diffraction measurements; thermogravimetric, compositional and surface area analyses, and scanning electron microscopy. The structure, composition, and morphology depended on the synthesis temperature. Batch kinetics experiments for the removal of strontium from aqueous solutions were performed, and the data were fitted by a pseudo-second-order reaction model and a diffusive model. The strontium extraction capacity also depended on the synthesis temperature and exhibited a maximum for samples synthesized at 100°C. The sorption process occurs in one or two diffusion-controlled steps that also depend on the synthesis temperature. These diffusion-limited steps are the boundary-layer diffusion and intra-particle diffusion in the case of pure nonatitanate synthesized at temperatures lower than 170°C, and only intra-particle diffusion in the case of nonatitanate synthesized at 200°C.

Mechanisms of strontium removal by a Ba-titanate material for the wastewater treatment

“…The two diffraction patterns are typical of a pure sodium titanate material [27] with four diffraction lines at 2θ = 9.5° (10° for the Na-titanate), 24°, 28° and 48°. The broad lines indicate that the two materials have a low crystallinity.…”

Sr2+ sorption property of seaweed-like sodium titanate mats: effects of crystallographic properties

“…As the basic reaction principle in the past, the sorption mechanisms of ion-exchange reactions with cations and Na + /H + in titanate were well demonstrated, and the inuencing factors on the mechanism have been discussed. 14,17,31,32,34 However, despite numerous reports on the relationship between ion-exchange reactions and crystal structure, effects of differences in the crystal structure depending on the composition of sodium titanate and on the sorption mechanisms, including ion-exchange, adsorption, and precipitation, are still unclear. To investigate the optimal synthesis condition of the SST, we organised the effects of the crystallographic properties of sodium titanates on the sorption properties of Sr 2+ as shown below.…”

“…[31][32][33] However, only a few reports have discussed the relationship between the sorption behaviour of cations and crystallographic properties from the perspective of ion-exchange effectiveness. 31,32,34 The removal efficiency of sodium titanates for several cations, including heavy metals and radionuclides, has been reported. 9,[14][15][16][17] Recently, the Sr 2+ adsorption selectivity of sodium nonatitanate (Na 4 Ti 9 O 20 ) and sodium trititanate (Na 2 Ti 3 O 7 ) were investigated by Kunishi et al 35 Although several references have reported on the mechanism of sodium titanate sorption, it is interesting to note that the ion-exchange reaction has been the focus for the cation removal by sodium titanates, while other reactions, such as precipitation or surface adsorption, have been overlooked.…”

Electrospun sodium titanate fibres for fast and selective water purification

“…Although sodium titanates are generally considered as typical weakly acidic ion exchangers [4,9], some debate on the exact sorption mechanism still remains. Merceille et al have reported that sorption mechanism has to be described by two models: the reaction kinetic model and the diffusion model [10]. They concluded from their kinetic experiments that the ion exchange is due to the chemisorption and not due to the physisorption.…”