Snowwhite2 paper: Understanding the mechanisms of gold(III) adsorption

In this installment of our series showcasing the impact of the Snowwhite SLS 3D printer on scientific advancement, we’re focusing on the paper “Understanding the mechanisms of gold(III) adsorption onto additively manufactured polyamide adsorbent, AM-N12“. We’ll kick things off by breaking down the study’s purpose and its key outcomes in plain language, ensuring everyone can grasp the significance of the research. Then, for those interested in the technical details, we’ll present the original abstract and any associated references.

Understanding the study and its main result

This scientific paper looks at how well a special type of plastic material, made using our Snowwhite2, can grab gold (specifically, gold with a +3 charge, written as gold(III)) from solutions that contain many different metals. The researchers found that the plastic works best at a very acidic condition (pH 0) for capturing the most gold. Even when other metals like platinum, palladium, copper, and others were present in the solution, the plastic was very good at picking out only the gold.

The way the gold sticks to the plastic seems to be mainly in a single layer. The speed at which the gold attaches to the plastic follows common patterns. Computer modeling suggests that the gold(III) might stick to the plastic through different forces, including negative charges repelling each other (anion-anion interaction), positive and negative charges attracting (electrostatic attraction), and a weaker type of bond called hydrogen bonding.

When they looked closely at the plastic after it had captured gold, they found that some of the gold(III) had changed into gold with a +1 charge (gold(I)), and even some pure gold metal (gold(0)). This means a chemical reaction happened where the gold was reduced. Lastly, they were able to remove about half of the captured gold from the plastic using a mixture of chemicals, and they could reuse the plastic again.

Main result

The main discovery is that this specifically designed 3D-printed plastic material (AM-N12) is highly selective for capturing gold(III) from complex mixtures of metals. Importantly, the researchers also found that during the capture process, some of the gold(III) is converted into lower forms of gold (gold(I) and gold(0)) on the surface of the plastic. This suggests that the plastic not only adsorbs the gold but also plays a role in a chemical reduction reaction. They also showed that the gold can be partially removed and the plastic can be reused.

Understanding the mechanisms of gold(III) adsorption onto additively manufactured polyamide adsorbent, AM-N12

Asiia Hurskainen (a), John Kwame Bediako (a), Youssef El Ouardi (a), Morad Lamsayah (b), Janne Frimodig (c), Eveliina Repo (a)
a) Department of Separation Science, School of Engineering Science, Lappeenranta-Lahti University of Technology (LUT), FI-53850 Lappeenranta, Finland
b) Laboratory of Applied and Environmental Chemistry (LCAE), Faculty of Science, University Mohammed First, 60 000 Oujda, Morocco
c) Department of Chemistry, University of Jyväskylä, P.O. Box 35, FI-40014 Jyväskylä, Finland

Ref.: https://www.sciencedirect.com/science/article/pii/S0009250924014301

Abstract

The focus of this paper is to study the adsorption behavior and mechanisms of gold(III) onto additively manufactured polyamide adsorbent, AM-N12 from synthetic multimetal leached solutions. Study of the effect of pH revealed that pH 0 was the optimum condition for reaching maximum gold(III) adsorption. In competitive mixtures containing Au(III) and other metal ions, i.e., Pt, Pd, Cu, Al, Fe, Pb, Sn, Ni, and Zn, extremely high selectivity towards Au ions was observed. Fitting of the adsorption isotherm data showed the order of Freundlich < Langmuir < Sips model, depicting likely monolayer adsorption process. Moreover, the kinetics data fitted well to the pseudo-first-order and pseudo-second-order models. Density Functional Theory (DFT) molecular modelling suggested anion–anion interaction, electrostatic attraction, and hydrogen bonding as possible adsorption mechanisms of gold(III). Furthermore, characterization and X-ray photoelectron spectroscopy (XPS) analysis indicated that after adsorption, portions of Au(III) were reduced to Au(I) and some portions were further reduced to Au(0), thus signifying reduction reaction. Finally, approximately 50 % of the adsorbed gold(III) was desorbed in 24h which was appro and the adsorbent regenerated using a mixture of 0.5 M thiourea and 1 M Hcl.