Molten salt mediated single-step synthesis of reusable nanostructured CaTiO3 for the removal and recovery of Sr2+: A potential adsorbent for the contaminated water bodies

Abstract

The facile synthesis approach for the adsorbent preparation and recyclability during decontamination of radioactive pollutants is a significant concern in water treatment. The objective of this study is to, synthesis via solid-state reaction of the nanostructured CaTiO₃ for the removal and recovery of strontium (Sr²⁺) from the various water sources. The influence of the adsorption-dependent parameters including, initial concentration, adsorbent dose, pH, contact time and co-existing ions interference were investigated. The prepared adsorbent was characterized by different analytical techniques like FT-IR, SEM with EDAX, TEM, TGA-DTG, Powder XRD and BET surface analysis. The kinetic models were also used, and according to the kinetic models, a pseudo-second-order kinetic model (R² = 0.999) was better fitted to the adsorption of Sr²⁺ ions onto CaTiO₃ rather than pseudo-first-order kinetics, which could properly represent the observed adsorption of Sr²⁺. For the isotherm study, the results are best fitted to the Langmuir isotherm model (R² = 0.98) with a maximum adsorption capacity of 102.04 mg/g. The common ions (Na⁺, Mg²⁺, Ca²⁺, and K⁺) and Sr²⁺ having a concentration of 1:2, 1:3, and 1:4, where 82.8, 79.5, and 68.2 % removal was achieved of Sr²⁺ in each respective matrix. In addition, the adsorption and corresponding recovery and removal for the different Sr²⁺spiked matrices in deionized water, tap water, well water, lake water, and seawater were investigated with 97, 65.6, 76.5, 73.9 and 17.8 % removal respectively. Also, the CaTiO₃ showed excellent recyclability with minimal loss even after 5 consecutive recyclability cycles and >90% removal of strontium achieved. Hence, prepared nanostructured CaTiO₃ could be considered a promising adsorbent for the removal and recovery of Sr²⁺ions from contaminated water bodies.

Keywords: Adsorption; Calcium titanate; Radioactive; Recovery; Recyclability; Strontium.