Electrochemical investigations of Pt−Hg and Cu−Hg alloys for mercury decontamination purposes
Typ
Examensarbete för kandidatexamen
Program
Publicerad
2021
Författare
Järlebark, Julia
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Mercury is a heavy metal of large environmental concern due to its potential to spread and
bioaccumulate and to its high toxicity for all living organisms. To date, there is no method
capable of efficient and sustainable removal of mercury from aqueous solutions under a wide
range of conditions. The focus of this thesis is to investigate several aspects of mercury
removal by electrochemical alloy formation between mercury and platinum or copper. Mercury
ions in the solution are reduced by the application of an electric potential, and form
an alloy with a solid platinum or copper electrode. Using an electrochemical quartz crystal
microbalance, the temperature dependence of the alloy formation between mercury and
platinum is studied in the range 20−60 C, and the apparent activation energy of the reaction
is determined to be 0.29 eV. Another purpose of the thesis is to relate the structure of
the electrode at various length-scales to the rate of mercury removal. The electrochemical
surface area is determined by underpotential deposition of hydrogen and by measurements
of the electrical double-layer capacitance, and the electrode structure is studied using a
scanning electron microscope. Mercury removal rates are determined through batch experiments
with subsequent inductively coupled plasma mass spectrometry analysis. It can be
concluded that a surface area with feature size of the order of 1 mm, e.g. a metal foam,
generates an enhanced rate of mercury removal. On the other hand, a nanoporous material
with feature size of the order of 100 nm, such as platinum black, does not contribute
to an increased mercury removal rate. Two case studies investigating the applicability of
the technology are also performed within the thesis; removal of mercury from concentrated
sulphuric acid produced by Boliden in the commercial smelting plant in Kokkola and from
scrubber liquids from a combined heat and power plant. Mercury is successfully removed
from the scrubber liquids using platinum coated titanium fibre electrodes, and from the
sulphuric acid using platinum coated stainless steel electrodes. In the case of the sulphuric
acid, it is also demonstrated that the process can be scaled up 400 times without loss of
efficiency.
Beskrivning
Ämne/nyckelord
mercury , heavy metal , electrochemistry , alloy , decontamination , water treatment