info:eu-repo/semantics/doctoralThesis
Synthesis of superparamagnetic magnetite nanoparticles functionalized with chemical groups derived from amines and acids. Evaluation of their adsorption effectiveness of lanthanide ions, molybdenum and rhenium in aqueous solution
Autor
Gaete-Carrasco, José Samuel
Institución
Resumen
This PhD thesis entitled "Synthesis of superparamagnetic magnetite nanoparticles
functionalized with chemical groups derived from amines and acids. Evaluation of their
adsorption effectiveness of lanthanide ions, molybdenum and rhenium in aqueous solution",
has as main objective to synthesize and use these materials in the recovery of metallic
elements of interest from dilute aqueous solutions.
In Chapter 2 the synthesis and characterization of magnetite nanoparticles functionalized
were studied. For nanoparticles functionalized with amine derivatives, NPM-AT and
NPM-AC2, characterization by HR-TEM indicated average sizes around 6-8 nm. Magnetism
curves analysis indicated that both functionalized nanoparticles have superparamagnetic
behavior. The zeta potential results evidenced a superficial change on the nanoparticles due
to the particles coating, being possible to confirm the amine-derived groups presence in them
using FTIR and XPS techniques.
For nanoparticles functionalized with acid derivatives groups, NPM-ACO and NPM-APO,
the characterization by HR-TEM allowed to determine sizes in 6.8-7.4 nm range. These
functionalized nanoparticles showed superparamagnetic behavior. Zeta potential
measurements showed a change on the surface of nanoparticles, likely due to the organic
coating. FTIR and XPS analysis evidenced the presence of acid derived groups in the
nanoparticles.
In Chapter 3 the metal ions adsorption effectiveness in aqueous solution using functionalized
nanoparticles was studied. In the Re(VII) and Mo(VI) adsorption experiments, NPM-AC2
had a higher adsorption capacity towards both metals compared to NPM-AT. Selectivity
studies indicated that both adsorbents present a higher adsorption towards Mo(VI) than for
Re(VII) from bimetallic aqueous solutions. In equilibrium studies, a good fit with the three
proposed models was achieved, suggesting that the adsorption process with both adsorbents
would be governed by a hybrid Langmuir-Freundlich mechanism. With respect to the kinetic6
studies, a pseudo-second order model fitted well the experimental adsorption data of Re(VII)
and Mo(VI) using both adsorbents. In addition, desorption studies were carried out, achieving
highest desorption efficiency at pH 13. Reuse studies of were also carried out in successive
cycles, demonstrating that NPM-AT and NPM-AC2 can be reused at least up to five times.
In the second part of Chapter 3, La(III), Pr(III) and Sm(III) adsorption by NPM-ACO and
NPM-APO was studied. In all the experiments, NPM-APO presented a higher adsorption
capacity towards the three lanthanide ions compared to NPM-ACO. With respect to
equilibrium studies, Freundlich model was well adjusted to the experimental data
corresponding to the first zone of adsorption curve of the lanthanide ions using NPM-ACO.
On the other hand, the three proposed models explained adequately La(III), Pr(III) and
Sm(III) adsorption equilibrium behavior using NPM-APO. In kinetic studies it was
determined that the pseudo-second order model adequately represents the adsorption kinetics
of three lanthanide ions with both adsorbents. Desorption studies indicated that a higher
percentage of desorption is achieved at pH 3, using H2SO4 solution. Finally, NPM-ACO and
NPM-APO could be reused in at least five cycles.
As a conclusion, from the results described in this study, it can be stablished the feasibility
of obtaining functionalized nanoparticles which can be used as adsorbents for metal ions
recovery and concentration from aqueous solutions.