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Advances in applied electrokinetics: Treatment, by-products reuse and sensors’ system
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Some of the barriers for a paradigm change on water reuse solutions are related to their maturing
technology level, to the removal of emerging organic contaminants and to the availability of rapid,
reliable and cost-effective monitoring tools. Thus, in this dissertation, electro-based techniques were
applied to secondary effluents aiming to promote water reuse through the (i) removal of triclosan and
inorganic contaminants, (ii) development and test of electronic tongue sensors that may be used as
complementary monitoring tools coupled with degradation processes, and (iii) enhancing of the
technology maturity level with the recovery of self-produced hydrogen and freshwater replacement in
the production of construction materials.
With these objectives, the main findings in this PhD project are described hereunder:
(i)
Electrochemical reactors are effective for degrading triclosan and its by-products. The
type of electrodes is an important variable that strongly impacts the degradation
efficiency, the kinetics and the by-products generated after treatment;
GC/MS/MS selectivity and sensitivity allows, after operational optimization, the
detection and quantification of triclosan, without the analyte derivatization, in the
effluent at ng/L level, showing that standard methods should be adjusted “case-bycase”.
(ii)
Electronic tongues coated with organic polyelectrolyte thin films are able to distinguish
at pico-molar resolution, by means of principal component analysis, between mineral
water and secondary effluent matrices and discriminating triclosan at different
concentrations;
The coating’s stability is affected by characteristics of the water to be analysed (e.g.
such as pH and elements content), rather than by the molecule to be detected; Due to
this dependency, sputtering thin films, more robust and stable, should be added to the
electronic tongue array;
A customized electronic tongue proved be a potential complementary monitoring tool
to follow the degradation pathway of the target compounds across the treatment,
when coupled to a dynamic electrochemical reactor; It was possible to semi-quantify
methyl-triclosan and triclosan using the array, whereas for phenolic compounds (2,4-dichlorophenol and 2,4,6-trichlorophenol) best results were obtained by using a single
sensor and thinner film as coating.
(iii)
The remediation process by-product, hydrogen, showed, on a proof of concept level,
its potential to be stored, reused or used as fuel in a proton-exchange membrane fuel
cell, to generate energy;
The use of electro-treated effluent showed to be sustainable for replacing freshwater
in construction materials production. This replacement can provide high quality
materials with features that are valued by construction materials industry, increasing
the market value of the reactor developed.
Descrição
Palavras-chave
water electrochemical processes emerging organic contaminants real time monitoring electronic tongue’s systems hydrogen