Investigation of interaction behaviours of cesium and strontium ions with engineering barrier material to prevent leakage to environmental

New Process for the Sulfonation of Algal/PEI Biosorbent for Enhancing Sr(II) Removal from Aqueous Solutions-Application to Seawater

Sulfonic resins are highly efficient cation exchangers widely used for metal removal from aqueous solutions. Herein, a new sulfonation process is designed for the sulfonation of algal/PEI composite (A*PEI, by reaction with 2-propylene-1-sulfonic acid and hydroxylamine-O-sulfonic acid). The new sulfonated functionalized sorbent (SA*PEI) is successfully tested in batch systems for strontium recovery first in synthetic solutions before investigating with multi-component solutions and final validation with seawater samples. The chemical modification of A*PEI triples the sorption capacity for Sr(II) at pH 4 with a removal rate of up to 7% and 58% for A*PEI and SA*PEI, respectively (with SD: 0.67 g L^-1). FTIR shows the strong contribution of sulfonate groups for the functionalized sorbent (in addition to amine and carboxylic groups from the support). The sorption is endothermic (increase in sorption with temperature). The sulfonation improves thermal stability and slightly enhances textural properties. This may explain the fast kinetics (which are controlled by the pseudo-first-order rate equation). The sulfonated sorbent shows a remarkable preference for Sr(II) over competitor mono-, di-, and tri-valent metal cations. Sorption properties are weakly influenced by the excess of NaCl; this can explain the outstanding sorption properties in the treatment of seawater samples. In addition, the sulfonated sorbent shows excellent stability at recycling (for at least 5 cycles), with a loss in capacity of around 2.2%. These preliminary results show the remarkable efficiency of the sorbent for Sr(II) removal from complex solutions (this could open perspectives for the treatment of contaminated seawater samples).

Hydroxyapatite nanoparticle functionalized activated carbon particle electrode that removes strontium from spiked soils in a unipolar three-dimensional electrokinetic system

Biohazard performance of Sr radionuclide can be significantly magnified by its release from the contaminated sedimentation. In this study, hydroxyapatite nanoparticle-functionalized activated carbon electrode (AC-HAP) was synthesized and stacked to the cathode compartment of the electrokinetic (EK) system to develop a unipolar three-dimensional (3D) electrochemical process for Sr²⁺ removal from spiked soils. Sr²⁺ adsorption by AC-HAP can be fitted by the pseudo-first-order and pseudo-second-order kinetic models and the Langmuir, Freundlich, and Temkin isotherm models. The largest monolayer adsorption capacity of AC-HAP of 69.49 mg g^-1 was evaluated in the pH range of 10-12 and at 40 °C. 3D EK further intensified the adsorption process of AC-HAP and the corresponding Sr²⁺ removal from aqueous environments. Voltage gradients and proposing time had a significant effect on the migration and transmission of Sr²⁺ in the electrolyzer. The influence of competitive ions on Sr²⁺ removal in the stock solutions followed Al³⁺ < Mg²⁺ < K⁺ < Na⁺ < Ca²⁺ while followed Al³⁺ < Na⁺ < K⁺ < Mg²⁺ < Ca²⁺ in 3D EK. The first three cycles for AC-HAP had taken roughly 50% of the reusability percentage. Sr²⁺ removal from spiked samples in 3D EK was achieved by acid dissolution, electromigration, and selective uptake on particle electrode.

Comparative study of strontium adsorption on muscovite, biotite and phlogopite

Micaceous minerals are the natural materials that can block radioactive strontium (Sr) released in the environment, and their adsorption capacity and mechanism are highly divergent owing to the different properties of micas. In this work, we comparatively studied the adsorption of Sr(II) on three typical micas, muscovite, biotite and phlogopite. The effects of pH, contact time, ionic strength, and background electrolyte were evaluated. It was found that phlogopite and muscovite had the largest solid-liquid distribution coefficient (K_d) for a reaction time of 48 h under acidic and alkaline conditions, respectively. Under alkaline conditions, as the reaction time increased to 44 days, phlogopite and muscovite showed the highest and lowest K_d, respectively. The K_d for Sr(II) adsorption on biotite and phlogopite increased with increasing pH but decreased with increasing pH for muscovite. X-ray diffraction analysis revealed that the interlayer weathering of phlogopite (a new diffraction peak appeared at 2-theta of ~6.1°) occurred along with the adsorption of Sr(II) below pH 9.0 under 0.01 mol/L NaCl. Furthermore, the adsorption of Sr(II) was significantly inhibited in the presence of 10^-5 and 10^-2 mol/L Cs⁺, resulting in similar adsorption capacity for phlogopite and muscovite at pH ~4.1. Consequently, the difference in Sr(II) adsorption on muscovite, biotite and phlogopite mainly came from the synergistic process of adsorption and weathering, which induced the differences in availability of interlayer sites among micas over a certain time.