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Publishable Summary
The aim of the PolarClean project was to study new efficient methods to remove emerging polar
contaminants from wastewater and drinking water (Objective 1), and to use the principles governing
the uptake of such contaminants to create pre-concentration methods for monitoring purposes
(Objective 2). The safety of the most successful prototypes has been assessed in vitro and the
purification process has been scaled up which brings the technology closer to practically solving real
water purification problems (Objective 3).
The quality of drinking water and aquatic ecosystems is threatened by anthropogenic polar organic
contaminants.
The
aim
of
the
PolarClean
project
(http://www.brighton.ac.uk/set/research/projects/PolarClean.php) was to develop new methods for
the removal and monitoring of emerging polar contaminants in waste and drinking water. These new
methods have been tested against a range of polar emerging contaminants representing pesticides,
hormones, pharmaceuticals and plasticisers with distinctive chemical structure and functionalities,
and nanoparticles. The properties of the materials with higher removal capacity have been applied in
the development of new analytical tools for trace contaminant detection.
Synthetic phenolic carbon materials with controlled pore structure and surface chemistry have been
developed and identified as highly efficient water purification tools that with some degree of
selectivity, can remove of polar organic contaminants by adsorption. The interconnected and
abundant micro and mesoporosity together with the low charged surface have been identified as
features that boost the removal capacity of these adsorbents compared to the granular activated
carbon (GAC) currently used in tertiary treatment in water treatment plants. This part of the work,
with special emphasis on the removal of a contaminant that is particularly challenging to treat,
metaldehyde, has been carried out in collaboration with an SME (MAST Carbon International Ltd.). As
an example of the enhanced performance of the synthetic carbon, the maximum adsorptive capacity
achieved for metaldehyde (75 mg/ g carbon), atrazine (641 mg/ g carbon), malathion (682 mg/ g
carbon), diclofenac (65 mg/g carbon) and estradiol (46 mg/g carbon) outperformed the treatment
obtained with standard granulated carbon used in the water industry when tested under the same
conditions. Relevant studies for up scaling the technology to industrial scales have been carried out,
such as adsorption isotherms; adsorption with presence of competing ions; through flow studies;
kinetic of adsorption; in-vitro toxicity of the water filtrate; characterisation and treatment of the sub
products in the production of the synthetic carbon and regeneration studies of the sorbents. The
technology was selected by the Technology Approval group (http://www.isleutilities.com/tag.php) as
one of the more innovative in Europe in 2012 among the 500 technologies annually reviewed
(London, December 2012). Currently, the synthetic carbon materials are being tested at pilot scale in
collaboration with the Water Industry (UK) and compared with other technologies for the removal of
metaldehyde as well as for other organic contaminants and the results so far indicate that its
performance is competitive and has potential to be used in water treatment plants. A patent was filed
in November 2012 “Carbon materials and their applications GB 1221227.0” between the University
of Brighton and MAST Carbon International Ltd.
The physico-chemical features found to be important in the synthetic carbon for the removal of polar
emerging contaminants have also assessed in various natural materials. Hence, agricultural crop byproducts with low commercial value but with advantageous natural coatings and porosity have been
studied and assessed for their use in water clean-up. This is the first time to our knowledge that the
purification of organic contaminants by these natural materials has been explored and could imply an
SEVENTH FRAMEWORK PROGRAMME, THE PEOPLE PROGRAMME
INTRA-EUROPEAN FELLOWSHIPS (IEF)
advance in water treatment in regions with limited resources as well as to obtain value and use to
agricultural “wastes”.
Carbon nanoparticles such as carbon nanotubes (single and multi-walled), with a range of oxidation
degrees, have shown lower adsorption properties than the above mentioned micro- mesoporous
synthetic carbon micro beads probably because of the limited pore size range. Single and multilayered graphene oxides have also been evaluated for their potential to remove estradiol, atrazine
and metaldehyde but the adsorptive capacity was lower than that found in the above mentioned
synthetic carbon which has controlled and “tunable” micro- and mesoporosity. The high cost, limited
adsorption and safety concerns of free nanopaticles limit their applicability for the purification of
water effluents in treatment plants. Nevertheless single layer graphene oxide (SLGO) has been
observed to play a role in the degradation of organic contaminants assisted by hydrogen peroxide.
The fundamentals of this degradation mechanism have been studied for atrazine and metaldehyde;
however, whereas atrazine removal was caused by both degradation and adsorption, metaldehyde
did not adsorb onto graphene (pH 5-14) and this allowed detailed examination of catalytic
degradation assisted by SLGO. The role of iron cations, pH and amount of the carbon nanomaterial
on the degradation of metaldehyde have been investigated, and the optimal performance was found
at 0.1mg SLGO/ml water, whereas pH and iron cations were not found to be critical parameters. The
possibly catalytic reaction carried out by SLGO has been found to cause degradation at a similar rate
to that from the Fenton’s reaction using iron sulphate and hydrogen peroxide and pH 5-8. The
potential to incorporate SLGO in water treatment has been further evaluated by physically attaching
it to a polymer matrix and carrying out the degradation of metaldehyde in a sequence of batch
reactions.
Nanoparticles can also be considered a polar emerging contaminant since they are being
incorporated in products of daily use (cloths, toothpaste, paints) and have application in
nanomedicine or environmental remediation, and their fate and toxicity is not well understood in
some cases. The Polarclean project has allowed studying the fate of some metal oxide nanoparticles
currently used when in contact with epithelial cells and their effect on cell proliferation and
metabolism. Besides, a new method based on their entrapment from water and dry surfaces within a
self-assembly polymer from marine origin has been developed.
A new analytical methodology based on LC-MS (multiresidue determination of 15 emerging
contaminants) and fast determination of a single contaminant with FTIR, have been developed to
assess the water purification achieved with the studied water treatment methods. The structure and
composition of the synthetic carbon beads that have shown to be so effective in water purification, as
well as some agricultural waste products, have been used as solid phase extraction analytical preconcentration tools. For this application, the carbon beads have been embedded in different shapes
of macroporous polymer (acrylamide, polyvinyl alcohol and hydroxyethyl metacrylate), a matrix that
holds the adsorptive phase and does not prevent the diffusion of the polar contaminants from the
water to the core of the analytical tool.
The new water treatment methods developed have potential to substitute the GAC used today in
water treatment plants and provide water with the lowest level of micropollutants possible. These
carbons can be a solution to the background level of pollution in ground and surface water present
for decades; with further research they could substitute the Fenton’s reaction in waste water
treatment plants and avoid or minimise the addition of iron for catalytic degradation (SLGO) and be
able to capture nanoparticles (self-assembly polymer); provide cleaner water in river basins and
developing countries (via adsorption onto agricultural waste materials); and become a new
SEVENTH FRAMEWORK PROGRAMME, THE PEOPLE PROGRAMME
INTRA-EUROPEAN FELLOWSHIPS (IEF)
generation of analytical tools. The results achieved in the PolarClean project have a clear socioeconomic impact and provide a step forward in the state of the art in water research.