Synthesis of 3D hierarchical flower-like calcium sulfate microspheres for cadmium removal from wastewater

Novel three-dimensional hierarchical flower-like calcium sulfate microspheres (CSMs) were successfully prepared with the assistance of polyethylene glycol, trisodium citrate, and polyacrylic acid. The CSMs were monodispersed as flower-like microspheres constructed from interspersed nanosheets. Their average diameter and Brunauer–Emmett–Teller specific surface area were 15 μm and 16.09 m2/g, respectively. The prepared CSMs were employed as adsorbents in cadmium (Cd(II)) removal from wastewater and their Cd(II) adsorption performances were analyzed. The adsorption kinetic data were best fitted to the pseudo-first-order kinetic model and the experimental isotherm data were precisely fitted to the Freundlich isothermal model. The maximum adsorption capacity of the CSMs could reach up to 18.13 mg/g at 293 K under neutral conditions, affirming the potential utility of the CSMs in Cd(II) removal from wastewater. 3D hierarchical flower-like calcium sulfate microspheres (CSMs) were prepared by a simple one-pot method with CaCl2 and Na2SO4 as the raw materials. Crystal shape guides leading to complex crystal morphologies (PEG, TSC, and PAA) were adsorbed on the surfaces of the calcium sulfate crystals, causing differences in the growth rates of the different crystal faces and the formation of flower-like microspheres. The prepared CSMs were employed as adsorbents in cadmium (Cd(II)) removal from wastewater. The Cd(II) was completely adsorbed within 10 min at 20°C-25 °C, affirming the potential utility of the CSMs in Cd(II) removal from wastewater. [Display omitted] •3D flower-like calcium sulfate microspheres (CSMs) were successfully synthesized.•Formation of CSMs was because of the selective adsorption of the PEG, TSC, and PAA.•The maximum adsorption capacity of the CSMs could reach up to 18.13 mg/g.•Pseudo-first-order kinetic model accurately described the adsorption kinetic data.