Fabrication of calcium oxalate with novel hierarchical structures mediated by amphiphilic phosphoproteins and its adsorptive removal of Congo red from aqueous solution

Abstract

Here, we developed a facile and green method to fabricate porous double cashew-shaped calcium oxalate (CaOx) in the presence of amphiphilic phosphoproteins. The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier transform infrared (FTIR) spectroscopy. The influences of the protein concentration and pH on the final morphology and phase transformation of CaOx crystals were systematically studied. A possible formation mechanism of the porous double cashew-shaped CaOx was proposed. Furthermore, the environmentally friendly and cheap CaOx with hierarchical structures exhibits high efficient and selective adsorption of Congo red. The high efficiency and selectivity is attributed to the unique structure, and the hydrogen bond between Congo red and the embodied proteins in double cashew-shaped CaOx.