Poly-thiosemicarbazide Membrane for Gold Adsorption and In-situ Growth of Gold Nanoparticles

摘要

In this work the synergy between a polymer containing chelate sites and goldions was explored by the fabrication of a polymeric membrane with embedded goldnanoparticles inside its matrix and by developing a process to recover gold fromacidic solutions. After realizing that the thiosemicarbazide groups present in themonomeric unit of poly-thiosemicarbazide (PTSC) formed strong complexes with Auions, membrane technology was used to exploit this property to its maximum.The incorporation of metal nanoparticles into polymeric matrices with currenttechnologies involves either expensive and complicated procedures or leads to poorresults in terms of agglomeration, loading, dispersion, stability or efficient use of rawmaterials. The fabrication procedure described in this thesis solves these problemsby fabricating a PTSC membrane containing 33.5 wt% in the form of 2.9 nm goldnanoparticles (AuNPs) by a three step simple and scalable procedure. It showedoutstanding results in all of the areas mentioned above and demonstrated catalyticactivity for the reduction of 4-Nitrophenol (4−NP) to 4-Aminophenol (4−AP).The current exponential demand of gold for electronics has encouraged the developmentof efficient processes to recycle it. Several adsorbents used to recover gold fromacidic solutions can be found in the literature with outstanding maximum uptakes,yet, poor kinetics leading to an overall inefficient process. The method developedin this dissertation consisted in permeating the gold-containing solution through aPTSC membrane that will capture all the Au ions by forming a metal complex withthem. Forcing the ions through the pores of the membrane eliminates the diffusionlimitations 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 tocapture >90% of the precious metal present in a solution of 100 ppm Au. The maximumuptake achieved without sacrificing the mechanical stability was 5.4 mmol/g.The selectivity between gold and copper (the most common unwanted metal presentalong with gold) was 6.7 for 100 ppm initial concentration of both metals and 14.6for 500 ppm.