367
1980, 1982). To explain the adsorption results, the mechanisms integrated not only
the presence of inclusion due to cyclodextrin cavities but also the effects of electrostatic interactions and van der Waals forces due to the presence of new reactive
groups on the surface particles. We have also introduced the presence of pollutantpollutant hydrophobic interactions that could explain the adsorption properties.
However, depending on the experimental conditions used in the batch method, the
mechanisms are more complex because other interactions such as ion exchange and
chemical microprecipitation may also play a role (Crini 2005a, 2006). All these
interactions have been discussed in two comprehensive reviews published in the
journal Progress in Polymer Science (Morin-Crini and Crini 2013; Morin-Crini
et al. 2018a).
In 2005, our group patented a process for the synthesis of cross-linked polysaccharides with ionic functional groups for the simultaneous removal of metals and
organic contaminants present at low trace levels in polycontaminated effluents
(Crini 2005b). The oligomer (cyclodextrin, linear dextrin) or polymer (starch) was
mixed with an epoxy cross-linking agent (1,4-butanediol diglycidyle ether) and
2,3-epoxypropyltrimethylammonium chloride in the presence of NH 4 OH at moderate temperature. During the cross-linking step with 1,4-butanediol diglycidyl ether,
polymer chains were cationized with 2,3-epoxypropyltrimethylammonium chloride. The cross-linked polymer had both hydroxyl, tertiary amino, and quaternary
ammonium groups with different degrees of substitution. The procedure gave beads
with excellent physical (e.g., high surface area, 100–150 m
2
g
−1
) and chemical properties (amphoteric in nature) and uniform and regular shape. The beads were easily
wettable, insoluble in water and in organic solvents, and stable in aqueous alkaline
or acidic solution. The modified materials possessed a remarkably high swelling
capacity in water due to the hydrophilic nature of its cross-linked units. Some
porous polymers were capable of swelling in both acidic and basic media, without
requiring modification of the pH. All these features were interesting for environmental applications (Crini 2005a, b; Delval et al. 2005; Renault et al. 2008; Charles
et al. 2010; Sancey et al. 2010).
The aminoethylation and carboxymethylation of cationic cross-linked materials
also enabled the preparation of amphoteric derivatives for possible use in the treatment of wastewater containing metals from surface treatment industries, dyes from
textile industries, or organic matter from the paper industry (Renault et al. 2008;
Charles et al. 2010; Sancey et al. 2010). The gels possessed typical amphoteric
characteristics, due to the protonation and deprotonation of the backbone tertiary
amine and pendant carboxyl groups in the polymer network. We proposed these
new amphiphilic polymers as complexing resins for the removal of organic matter,
turbidity, metals, and boron and fluoride ions from industrial wastewater. The gels
could be used over a wide pH range due to their particular electrical character. The
comparison with similarly prepared starch-based materials demonstrated the higher
capacity for organic compound adsorption, due to the formation of inclusion complexes between cyclodextrins and pollutants.
8 Water-Insoluble Cyclodextrin-Epichlorohydrin Polymers
1980, 1982). To explain the adsorption results, the mechanisms integrated not only
the presence of inclusion due to cyclodextrin cavities but also the effects of electrostatic interactions and van der Waals forces due to the presence of new reactive
groups on the surface particles. We have also introduced the presence of pollutantpollutant hydrophobic interactions that could explain the adsorption properties.
However, depending on the experimental conditions used in the batch method, the
mechanisms are more complex because other interactions such as ion exchange and
chemical microprecipitation may also play a role (Crini 2005a, 2006). All these
interactions have been discussed in two comprehensive reviews published in the
journal Progress in Polymer Science (Morin-Crini and Crini 2013; Morin-Crini
et al. 2018a).
In 2005, our group patented a process for the synthesis of cross-linked polysaccharides with ionic functional groups for the simultaneous removal of metals and
organic contaminants present at low trace levels in polycontaminated effluents
(Crini 2005b). The oligomer (cyclodextrin, linear dextrin) or polymer (starch) was
mixed with an epoxy cross-linking agent (1,4-butanediol diglycidyle ether) and
2,3-epoxypropyltrimethylammonium chloride in the presence of NH 4 OH at moderate temperature. During the cross-linking step with 1,4-butanediol diglycidyl ether,
polymer chains were cationized with 2,3-epoxypropyltrimethylammonium chloride. The cross-linked polymer had both hydroxyl, tertiary amino, and quaternary
ammonium groups with different degrees of substitution. The procedure gave beads
with excellent physical (e.g., high surface area, 100–150 m
2
g
−1
) and chemical properties (amphoteric in nature) and uniform and regular shape. The beads were easily
wettable, insoluble in water and in organic solvents, and stable in aqueous alkaline
or acidic solution. The modified materials possessed a remarkably high swelling
capacity in water due to the hydrophilic nature of its cross-linked units. Some
porous polymers were capable of swelling in both acidic and basic media, without
requiring modification of the pH. All these features were interesting for environmental applications (Crini 2005a, b; Delval et al. 2005; Renault et al. 2008; Charles
et al. 2010; Sancey et al. 2010).
The aminoethylation and carboxymethylation of cationic cross-linked materials
also enabled the preparation of amphoteric derivatives for possible use in the treatment of wastewater containing metals from surface treatment industries, dyes from
textile industries, or organic matter from the paper industry (Renault et al. 2008;
Charles et al. 2010; Sancey et al. 2010). The gels possessed typical amphoteric
characteristics, due to the protonation and deprotonation of the backbone tertiary
amine and pendant carboxyl groups in the polymer network. We proposed these
new amphiphilic polymers as complexing resins for the removal of organic matter,
turbidity, metals, and boron and fluoride ions from industrial wastewater. The gels
could be used over a wide pH range due to their particular electrical character. The
comparison with similarly prepared starch-based materials demonstrated the higher
capacity for organic compound adsorption, due to the formation of inclusion complexes between cyclodextrins and pollutants.
8 Water-Insoluble Cyclodextrin-Epichlorohydrin Polymers