In this work the synergy between a polymer containing chelate sites and gold
ions was explored by the fabrication of a polymeric membrane with embedded gold
nanoparticles inside its matrix and by developing a process to recover gold from
acidic solutions. After realizing that the thiosemicarbazide groups present in the
monomeric unit of poly-thiosemicarbazide (PTSC) formed strong complexes with Au
ions, membrane technology was used to exploit this property to its maximum.
The incorporation of metal nanoparticles into polymeric matrices with current
technologies involves either expensive and complicated procedures or leads to poor
results in terms of agglomeration, loading, dispersion, stability or efficient use of raw
materials. The fabrication procedure described in this thesis solves these problems
by fabricating a PTSC membrane containing 33.5 wt% in the form of 2.9 nm gold
nanoparticles (AuNPs) by a three step simple and scalable procedure. It showed
outstanding results in all of the areas mentioned above and demonstrated catalytic
activity for the reduction of 4-Nitrophenol (4−NP) to 4-Aminophenol (4−AP).
The current exponential demand of gold for electronics has encouraged the development
of efficient processes to recycle it. Several adsorbents used to recover gold from
acidic solutions can be found in the literature with outstanding maximum uptakes,yet, poor kinetics leading to an overall inefficient process. The method developed
in this dissertation consisted in permeating the gold-containing solution through a
PTSC membrane that will capture all the Au ions by forming a metal complex with
them. Forcing the ions through the pores of the membrane eliminates the diffusion
limitations and the adsorption will only depended on the fast complexation kinetics,
resulting in a very efficient process. A flux as high as 1868 L/h m2 was enough to
capture >90% of the precious metal present in a solution of 100 ppm Au. The maximum
uptake achieved without sacrificing the mechanical stability was 5.4 mmol/g.
The selectivity between gold and copper (the most common unwanted metal present
along with gold) was 6.7 for 100 ppm initial concentration of both metals and 14.6
for 500 ppm.
|Date of Award
- Physical Sciences and Engineering
|Klaus-Victor Peinemann (Supervisor)
- gold nanoparticles