Adsorption of strontium on manganese oxide (δ-MnO2) at elevated temperatures: experiment and modeling

Abstract

Strontium adsorption has been studied by the method of acid-base potentiometric titrations at three different temperatures: 25, 50, 75C. The effect of pH, ionic strength, sorbate/sorbent ratio, and temperature on adsorption was investigated. Experimental data were simulated using two various surface complexation models, with two different electrostatic descriptions of the interface: the constant capacitance model (CCM) and the triple-layer model (TLM). Although the both models used are able to account for the acid-base reactions and surface complexation of strontium on birnessite, we consider that the TLM is more applicable for a description of heterophaseous system H+ MnOH Sr2+. Under conditions of low ionic strength and negatively charged surface, Sr2+ ions compete with the electrolyte ions and form outer-sphere complexes along with inner-sphere complexes. Consequently, using the CCM for description of strontium adsorption data could be mathematically satisfactory, but physically senseless. The equilibrium model proposed here consists of the complexes of inner (MnOHSr2+, MnOSr+, MnOSrOH0) and outer types ([MnO Sr2+]+). The corresponding intrinsic equilibrium constants of the formation of these surface complexes were calculated for 25,50, and 75C.

Synthesis and Evaluation of Peptide–Manganese Dioxide Nanocomposites as Adsorbents for the Removal of Strontium Ions

“…When the temperature rises above 40 • C, the adsorption efficiency sharply decreases. This phenomenon may be due to the weakening of the interaction between IIGK@MnO 2 and Sr 2+ at higher temperatures, resulting in the desorption of Sr 2+ [31]. The contact time between IIGK@MnO2 and Sr 2+ would also affect the adsorption efficiency.…”

Synthesis, Characterization of Mn3o4: Adsorption Application and Antibacterial Evaluation

“…Thus, several types of adsorbents have been used to remove dyes such as clay minerals [33,34], carbon-based materials [35][36][37], and metal oxides [38,39]. Owing to the high surface charge density and the high sorption capacity, various Mn oxides (e.g., including pyrolusite (-MnO2) and birnessite (-MnO2)) have been extensively used as high efficient adsorbents to remove dyes [40][41][42][43].…”