Effectiveness of Calcium Deficiency in Nanosized Hydroxyapatite for Removal of Fe(II), Cu(II), Ni(II) and Cr(VI) Ions from Aqueous Solutions

Abstract

In this work, nanosized calcium deficient hydroxyapatite (nCDHA) was synthesized by the precipitation method, and then utilized as an adsorbent for removal of Fe (II), Cu (II), Ni (II) and Cr (VI) ions from aqueous solutions after characterizing it by various techniques as scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and BET method. A possible structure of synthesized nCDHA was proposed. The adsorption study indicated that the adsorption equilibrium is well fitted with Langmuir isotherm model with the maximum adsorption capacities followed the order of Fe (II) > Cu (II) > Ni (II) > Cr (VI) with the values of 137.23, 128.02, 83.19 and 2.92 mg/g, respectively. The ion-exchange mechanism was dominant for the adsorption of metal ions onto nCDHA at initial metal concentrations lower than 0.01 mol/L. Along with the ion-exchange mechanism, there was an additional precipitation occurred on the surface of nCDHA in the case of Fe (II) and Cu (II) at initial concentrations higher than 0.01 mol/L.

La eliminación de metales tóxicos presentes en efluentes líquidos mediante resinas de cambio iónico. Parte XV: Iron(II)/H+/Lewatit TP208

“…The removal of iron(II) from aqueous solutions had been also of interest for various research groups, and particularly, several ion exchange resins and/or adsorbents were used recently in this role, i.e. 732-type strong acid cation exchange resin, in an ascorbic acid and EDTA medium, effectively loaded Fe(II) at acidic pH values (Zhou et al, 2018), multiwalled carbon nanotubes modified with EDTA, and also containing amino and car- boxyl groups removed Fe(II) from aqueous solutions (Desouky, 2018), whereas nanosized calcium deficient hydroxyapatite was other material used in the removal of this element from solutions (Van Dat et al, 2019). MTS9100, C107E, MTS9570 and MTS9501, TP214, MTS9301 ion exchange resins were used in the removal of iron(II) (and other metals) from solutions (Bezzina et al, 2019;Bezzina et al, 2020), in the case of these resins, the acid present in the aqueous solution had a definitive role in the removal (or not) of the various metal ions investigated.…”