Synthesis of strontium hydroxyapatite embedding ferroferric oxide nano-composite and its application in Pb2 + adsorption

A method of co-precipitation was used to synthesize a novel magnetic nano-composite strontium hydroxyapatite/ferroferric oxide (SrHAp/Fe3O4) by embedding ferroferric oxide into strontium hydroxyapatite and this SrHAp/Fe3O4 was utilized as adsorbent to remove Pb2+ from aqueous solutions. The morphology features at the micro level of the obtained adsorbent were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) surface area and Fourier transform infrared (FTIR). The maximal immobilization capacity of Pb2+ reached to 1249mg/g at the optimum adsorption conditions (dosage of 0.2mg/mL, contact time for 20min, pH at 4.5 and temperature at 25°C). Adsorption of Pb2+ onto SrHAp/Fe3O4 agreed well with the pseudo-second order model (R2=0.9997). For adsorption isotherms, the Freundlich isotherm was provided to be the best correlation (R2=0.9862) compared to the Henry and Langmuir isotherms. The thermodynamic parameters (ΔG<0, ΔS=21.8215J/mol/K, ΔH=0.1789kJ/mol) indicated that adsorption process was a spontaneously endothermic reaction. Furthermore, the adsorbent, SrHAp/Fe3O4 was good in terms of anti-interference through the interference of coexistence metal cation experiment.