Claudia Maria Simonescu, Alina Tatarus, Christu Tardei, Delia Patroi, Mioara Dragne, Daniela C. Culita, Rodica-Elena Patescu, Laurentiu Teodor Busuioc, Ioana Melinte<br>Nano and Micro-hydroxyapatite Particles for Lead <br>Removal from Wastewater

Claudia Maria Simonescu, Alina Tatarus, Christu Tardei, Delia Patroi, Mioara Dragne, Daniela C. Culita, Rodica-Elena Patescu, Laurentiu Teodor Busuioc, Ioana Melinte
Nano and Micro-hydroxyapatite Particles for Lead
Removal from Wastewater

Abstract:

Two types of (Ca10(PO4)6(OH)2) hydroxyapatite (HAP) powders with high purity were obtained using two different synthesis methods - a wet chemical synthesis method such as precipitation from aqueous solution and a dry chemical method such as solid-state sintering. Both types of powders were characterized by X-ray diffraction, FT-IR analysis, scanning electron microscopy (SEM), and N2 sorption analysis. X-ray diffraction showed that both HAP powders contain hydroxyapatite as the only crystalline phase. Data from X-ray diffraction were confirmed by FT-IR spectra. SEM images showed that nanometric size hydroxyapatite (nano-HAP) was obtained by precipitation from aqueous solution and hydroxyapatite with micrometric size (micro-HAP) was obtained using sintering method as a solid phase synthesis method. Nano-HAP powder has a BET surface area almost 5 times higher than that of the microcrystalline HAP powder. Consequently, both powders were comparatively tested in lead removal process from aqueous solutions. The contact time, the concentration of lead ions in the initial solution, pH and temperature were the main parameters studied. The highest Pb(II) sorption was achieved for nano-HAP. The sorption process was relatively fast because the equilibrium was achieved after about 60-180 min of contact depending on the lead concentration in the initial solution, and the specific surface area of the samples. Results showed that the adsorption behaviour of micro-HAP and nano-HAP follows the Langmuir isotherm. The kinetic process of Pb(II) sorption onto micro-HAP and nano-HAP was tested by applying the pseudo-first order, the pseudo-second order, and intraparticle diffusion models. The experimental data were fitted with pseudo-second order equation. The main mechanism for lead ions removal using synthesized micro-HAP and nano-HAP was suggested to be dissolution of HAP followed by hydroxy-pyromorphite (Pb5(PO4)3OH) precipitation. From this experimental study, it can be concluded that both sorbents can be successfully applied for lead removal from wastewater. Keywords: sintering, calcination, porosity, hydroxiapatite, environmental applications

Issue: 2015, Volume 66, Issue 5

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