Ultralight molybdenite-doped and phosphate rich alginate composites exhibiting superb chelating ability for UO22+: Adsorption thermodynamics, kinetics and mechanistic evaluation

Abstract

In the present research work, molybdenite-doped and phosphate-rich alginate composites (MDPA) were developed for uranium removal from aqueous medium and characterized through different analytical techniques such as XPS, FTIR, XRD, SEM-EDS, and elemental mapping. The mass ratio of molybdenite in different MDPA hydrogel beads was optimized, and it was concluded that MDPA-II material (having 22.5% w/w MoS2) has superb chelating ability for UO22+ ions from aqueous solution. The XPS data showed the involvement of S coordination with UO22+ species. It proves that the UO22+ ions bonded to MoS2 surfaces by forming a U-S bond. Moreover, phosphate (OPO3-) group of phytic acid and SMo=S linkages of molybdenite reinforced inner-spherical complexation with UO22+ ions. Kinetics followed pseudo-second-order rate model (R2≈0.99) and equilibrium sorption data found in close agreement with the Langmuir and Temkin models (R2≈0.99). The qm (mg/g) at 298 K was found to be 311.16±7.76 mg/g at optimized pH of 4.5. The study shows the improved sorption performance of MDPA-II hydrogel beads for the uranium competitive recovery.