373
2007; Crini et al. 2007; Crini 2008; Sancey et al. 2010, 2011a, b, 2012). These
cross-linked materials have been studied in pollutant complexing experiments, and
their different performances were compared. It was found that, in some cases, crosslinked starches and cross-linked dextrins had higher adsorption capacities than
cross-linked cyclodextrin polymers even if they did not have the type of cavity that
participates in the inclusion complexes. The density of the cross-linking mainly
explained these results. The cross-linking reaction creates a particular 3D macromolecular structure (recognized as difficult to control) forming a mesh that is also
susceptible to bind pollutants (Fig. 8.11). The polymer network therefore offers
cross-linked oligosaccharide and polysaccharide materials the possibility to sequester contaminants through effects of cooperation not only between cyclodextrin molecules but also via additional interactions in the mesh with diffusion into the network
(Morin-Crini et al. 2013, 2015, 2018a). These mesh interactions have a greater role
when the degree of cross-linking is lower, enabling the polymer to swell in water
and thus enhance diffusion of the contaminants through the network. Professors
Isasi and Yilmaz have carried out similar studies, which have led to similar
conclusions.
8.5 Conclusions
This chapter reviews the research conducted over the past 30 years by our research
group on water-insoluble cyclodextrin-epichlorohydrin polymers. It shows the
progress of our work and our contribution to a better understanding of these materials. Table 8.1 summarizes all our contributions on cyclodextrin polymers during the
period 1996–2019. Table 8.2 reports the ten most cited papers in the ISI Web of
Science and Scopus databases since 1998 with “cyclodextrin polymer” and “pollutant removal” in the topic of our works.
Cyclodextrin-epichlorohydrin polymers can be used as complexing adsorbents
to remove contaminants from polycontaminated effluents. They have several advantages: technological simplicity in their use, efficiency in the elimination of substances even at trace levels, easily recyclable (regeneration) or disposable
(incineration), and beneficial to the environment to reduce the impact/toxicity of an
effluent. However, as industrial production of cyclodextrin-epichlorohydrin polymers has not started, the materials produced at lab scale suffer from variability in
their characteristics. There is also a non-negligible cost difference with conventional materials such as activated carbon used in wastewater treatment. Therefore,
cyclodextrin polymer materials are basically at the laboratory study stage, and there
is still a lot of work to be done to demonstrate their potential on an industrial scale.
On this subject, the first study on the industrial-scale use of cyclodextrinepichlorohydrin polymers to remove emerging pollutants such as endocrine disrupters from wastewater treatment plant effluents has just been published (Fenyvesi
et al. 2020). Chemical abatement and toxicity mitigation of wastewater have shown
that adsorption on modified ECP materials can be an interesting additional
8 Water-Insoluble Cyclodextrin-Epichlorohydrin Polymers
2007; Crini et al. 2007; Crini 2008; Sancey et al. 2010, 2011a, b, 2012). These
cross-linked materials have been studied in pollutant complexing experiments, and
their different performances were compared. It was found that, in some cases, crosslinked starches and cross-linked dextrins had higher adsorption capacities than
cross-linked cyclodextrin polymers even if they did not have the type of cavity that
participates in the inclusion complexes. The density of the cross-linking mainly
explained these results. The cross-linking reaction creates a particular 3D macromolecular structure (recognized as difficult to control) forming a mesh that is also
susceptible to bind pollutants (Fig. 8.11). The polymer network therefore offers
cross-linked oligosaccharide and polysaccharide materials the possibility to sequester contaminants through effects of cooperation not only between cyclodextrin molecules but also via additional interactions in the mesh with diffusion into the network
(Morin-Crini et al. 2013, 2015, 2018a). These mesh interactions have a greater role
when the degree of cross-linking is lower, enabling the polymer to swell in water
and thus enhance diffusion of the contaminants through the network. Professors
Isasi and Yilmaz have carried out similar studies, which have led to similar
conclusions.
8.5 Conclusions
This chapter reviews the research conducted over the past 30 years by our research
group on water-insoluble cyclodextrin-epichlorohydrin polymers. It shows the
progress of our work and our contribution to a better understanding of these materials. Table 8.1 summarizes all our contributions on cyclodextrin polymers during the
period 1996–2019. Table 8.2 reports the ten most cited papers in the ISI Web of
Science and Scopus databases since 1998 with “cyclodextrin polymer” and “pollutant removal” in the topic of our works.
Cyclodextrin-epichlorohydrin polymers can be used as complexing adsorbents
to remove contaminants from polycontaminated effluents. They have several advantages: technological simplicity in their use, efficiency in the elimination of substances even at trace levels, easily recyclable (regeneration) or disposable
(incineration), and beneficial to the environment to reduce the impact/toxicity of an
effluent. However, as industrial production of cyclodextrin-epichlorohydrin polymers has not started, the materials produced at lab scale suffer from variability in
their characteristics. There is also a non-negligible cost difference with conventional materials such as activated carbon used in wastewater treatment. Therefore,
cyclodextrin polymer materials are basically at the laboratory study stage, and there
is still a lot of work to be done to demonstrate their potential on an industrial scale.
On this subject, the first study on the industrial-scale use of cyclodextrinepichlorohydrin polymers to remove emerging pollutants such as endocrine disrupters from wastewater treatment plant effluents has just been published (Fenyvesi
et al. 2020). Chemical abatement and toxicity mitigation of wastewater have shown
that adsorption on modified ECP materials can be an interesting additional
8 Water-Insoluble Cyclodextrin-Epichlorohydrin Polymers