Environmental assessment of a Palette Modular Device for gold recovery from PVD

Abstract

The novel “Palette Modular Device” (PMD) technology, addressing the recovery of wastes from Physical Vapour Deposition (PVD) maintenance, is evaluated according to a Life Cycle Assessent (LCA) approach. The PMD recovery technology was recently developed with the aim of an easier and more sustainable separation of the film layers used in PVD, with a particular emphasis on multi-material film productions, frequently adopted in the electronic industry. The PMD is briefly presented in the paper, along with three implementations for industrial purposes. Each implementation adopts a different light solvent for the metal recovery like acetone and formic acid. The usage of light solvents is a peculiar feature enabled by the system considered, as an alternative to traditional approaches. The LCA starts with the objectives and prosecutes with inventories of all material and energy flows for each different scenario considered. Additionally, a global impact assessment is provided in a specific section, in order to enable a quantitative comparison of the potential effects on the environment in every scenario. The results of this study allow the industrial designer to perform an overall environmental evaluation of the three strategies proposed and to compare the performances of the novel technology. The research, furthermore, highlights some critical points in the adoption of the PMD and suggests how to improve the implementation of this recovery process.

Keywords:

• Gold recovery
• thin film deposition
• Palette Modular Device
• life cycle assessment

Acknowledgments

The authors thank Mr Luca Scala for his expert technical help in accomplishing some of the experimental activities. Part of these activities was funded via the Regional Program “Principi Attivi”, along with awards granted by the Agenzia Regionale Tecnologia ed Innovazione (ARTI) in Apulia (ITA).

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1. For example, sandblasting, bead-blasting, etc.

2. Patented with ID US 20130008375 A1 by MRS™.

3. Authors address readers to this publication, for an in-depth comparison between PMD based and standard gold recovery practices in the field.

4. For example, in the following of this paper, we will make the hypothesis that gold forms a uniform layer on one of the palette sides.

5. The sonicator is a device that generates ultrasonic waves in a liquid medium, creating microscopic vacuum bubbles, which rapidly expand and compress themselves. This phenomenon is called cavitation, and acts as high speed miniature brushes.

6. With or without the PMD system embedded.

7. For example, consider the unmounting of the static shields/PMD, which can be done by hand.

8. The photopolymer is supplied by RS Components Ltd.

9. Given the trade secret of MRS about its sacrificial layer proprietary formulations, we have here made use of a commercial equivalent, exhibiting similar behaviour in the etching process, as a reference.

10. Notice that other references (SimaPro) – compared to the ones used here – predict a POCP potential as low as 0.1655 kg C₂H₄ eq., which is roughly half of the contribution in Table 4.

11. Starting from the work of Carter (Carter et al. 1993), several results against the influence of low concentrations of acetone vapors on the air quality have addressed the recent decision by US EPA to declassify acetone as “volatile organic compound” (VOC) of negligible reactivity.