Innovative free radical induced synthesis of WO3-doped diethyl malonate grafted chitosan encapsulated with phosphorylated alginate matrix for UO22+ adsorption: Parameters optimisation through response surface methodology

Abstract

The current research involves the development of a novel core–shell based hybrid material in which tungsten oxide (WO3) served as a solid core while diethyl malonate grafted chitosan intercalated in phosphorylated alginate as a shell. The prepared composites (DEM-g-CST) having different chemically modified chitosan to alginate mass ratio were lyophilized and thoroughly characterized through XRD, XPS, FTIR, SEM-EDS, and elemental mapping. The adsorptive potential of these acid base resistive DEM-g-CST materials was assessed in U(VI) competitive removal from aqueous solution. The free radical induced grafting of 1,3-dicarbonyl moiety over the CS linear chains increased the number of chelating groups. The 17 runs of adsorption tests were performed and then Box Behnken Design (BBD) was implemented to optimize the sorption capacity (qe) using the response surface methodology design layout. Among different composites DEM-g-CST-4 exhibited the superior sorption capacity (qm = 315 mg/g at 308 K and pH 4.5) and sorption data followed the Temkin and Langmuir model (R2 ≈ 0.997) while kinetic data was found in close agreement with pseudo-second-order rate model (R2 ≈ 0.996). Particularly, DEM-g-CST materials presented wide pH durability and mechanical resilience within alginate matrix. These features strongly suggest DEM-g-CST-4 to be an efficient contestant for uranium competitive recovery.