Investigation of Silver Recovery from Thin Film CIGS Solar Cells by Selective Leaching
Typ
Examensarbete för masterexamen
Program
Publicerad
2020
Författare
Fransson, Rasmus
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Recycling and green energy has become increasingly hot topics in research and
our everyday lives. One of the promising sources of green energy that is being
developed is CIGS thin film solar cells, the photovoltaic cell contains an alloy of
copper, indium, gallium and selenium where silver is used as a conducting material
on the surface. However, innovative and sustainable strategies to recover silver
from spent CIGS solar cells are still not readily available. Previous research has
shown strategies including pyrolysis and electrodeposition, both which are energy
consuming and require multiple steps prior to the separation stage. Reducing the
number of pre-treatment steps will play an important role in realizing sustainable
silver recovery. This study aims to investigate selective leaching as a feasible method
of recovering metals, especially silver, from CIGS solar cells. This was achieved by
combining thermodynamic investigation, analyzing old data combined with new
leaching experiments to design a statistical model. A second aim is to evaluate
different factors and their contribution to dissolution of silver. A model describing
the system as a function of time, acid concentration and solid to liquid ratio was
made using Design of Experiments (DOE) and Analysis of Variance (ANOVA). It
was shown that silver can be selectively leached by nitric acid with a resulting purity
above 90% after 1 h. The results show that the significant factors are time and
nitric acid concentration. The major co-dissolved metal component is indium but
low levels of tin is also found in the leachate. In the initial experiments of the study
it was found that oxalic acid leaching may be an alternative route for simultaneous
silver and indium recovery due to silver being precipitated while indium is found in
the leachate, but further research should be conducted.
Beskrivning
Ämne/nyckelord
Silver , selective leaching , CIGS , recycling , solar cells , nitric acid , organic acids , factorial design , statistical modelling