Highly efficient adsorption of strontium ions from aqueous solutions by hollow balls of oxidized graphene

I n this work, samples of oxidized graphene were synthesized by thermolysis of a mixture of saccharose, potassium nitrate, and sulfur. It was shown that oxidized graphene was formed during the thermolysis of saccharides. This was evidenced by FTIR and Raman spectroscopy. The main morphological and textural characteristics of the synthesized adsorbent were studied by constructing isotherms of low-temperature adsorption/desorption of nitrogen. The results were analyzed using the BET equation. The number of graphene layers in the samples was calculated. The elemental composition of the synthesized material and the presence of strontium ions on its surface after adsorption were determined by X-ray photoelectron spectroscopy (XPS). The adsorption of strontium ions was studied under batch conditions. The dependence of the adsorption of strontium ions on the duration of interaction of the aqueous solution of SrCl₂ with the surface of oxidized graphene was determined. The equilibrium adsorption of Sr²⁺ cations and the dependence of the adsorption of Sr²⁺ cations on the pH of the aqueous solution were also investigated. It has been shown that the kinetics of strontium ion adsorption are well described by a pseudo-first-order equation (R² = 0.9808). The equilibrium adsorption of Sr²⁺ ions can be described by the Langmuir equation (R² = 0.9882). The experimentally determined maximum adsorption value of Sr²⁺ cations is 421 mg/g. Based on the experimental adsorption data, the number of adsorption centers per unit area of this adsorbent (10 nm²) was calculated to be 48.2.