302
literature reports concern the use of anion exchangers to remove anionic dyes than
cation exchangers for adsorption of basic dyes.
Summing up, the dyestuff sorption on the anionic and cationic resins depends on
a few factors of which the most important are:
– Kind of the resin including its matrix composition and structure (macroporous,
gel), kind of functional groups (weakly, intermediate, and strongly basic), sorption capacity, as well as kind of bead and form in which the anion exchanger
is used.
– Sorption proceeds more quickly in the case of anion exchangers of more hydrophilic matrix (polyacrylic or phenol-formaldehyde) compared with their polystyrene counterparts; hydrophilic resins are more effective in organic substance
sorption due to their greater flexibility of matrix, the presence of carbonyl group,
and possibility of hydrogen bonds formation.
– The effect of functional groups basicity of macroporous anion exchangers on
their affinity for the dyes of various kinds can be presented as follows: strongly
basic anion exchangers type 1 > strongly basic anion exchangers type 2 > weakly
basic anion exchangers.
– Dye sorption kinetics is affected by matrix structure of ion exchangers; in the
case of dye sorption on the gel resins, the sieve effect consists in limited diffusion
of large-size dye ions in the pores of the resin of microporous structure.
– The main binding mechanism of dyes is ion-exchange reaction; physical and
hydrophobic π–π interactions (among benzene rings in dyestuff and resins
matrix) play a more significant role in case of the polyacrylic anion exchangers
such as Amberlite IRA 958, Amberlite IRA 458, and Amberlite IRA 67 in comparison to polystyrene ones; large sorption ability of anion exchangers resins
toward dyes results from H-bond formation (nitrogen from quaternary ammonium and oxygen from carbonyl functional groups of anion exchangers interact
with nitrogen from the -NH 2 group of dyes).
– A lack of evident impact of solution pH on dye uptake indicates that the process
of their bonding on the resin proceeds not only by ion pair formation between the
sulfonic groups of dyes and tertiary amine groups of the weakly basic anion
exchangers or the quaternary ammonium functionalities of strong base anion
exchange resins but also by the interactions of π–π type as well as hydrogen bonds.
– Kind of dye (composition and spatial structure, number and kind of chromophore, and auxochromium).
– Process conditions (kind of the dye-ion exchanger system, concentration of the
dye, phase contact time, presence of auxiliaries in the system, e.g., electrolytes
and surfactants, solution pH, temperature, rate of phases mixing or rate of flow
in the column system, desorption, as well as way of its conducting (static or
dynamic method) (Wawrzkiewicz and Hubicki 2015).
A. Wołowicz and M. Wawrzkiewicz
literature reports concern the use of anion exchangers to remove anionic dyes than
cation exchangers for adsorption of basic dyes.
Summing up, the dyestuff sorption on the anionic and cationic resins depends on
a few factors of which the most important are:
– Kind of the resin including its matrix composition and structure (macroporous,
gel), kind of functional groups (weakly, intermediate, and strongly basic), sorption capacity, as well as kind of bead and form in which the anion exchanger
is used.
– Sorption proceeds more quickly in the case of anion exchangers of more hydrophilic matrix (polyacrylic or phenol-formaldehyde) compared with their polystyrene counterparts; hydrophilic resins are more effective in organic substance
sorption due to their greater flexibility of matrix, the presence of carbonyl group,
and possibility of hydrogen bonds formation.
– The effect of functional groups basicity of macroporous anion exchangers on
their affinity for the dyes of various kinds can be presented as follows: strongly
basic anion exchangers type 1 > strongly basic anion exchangers type 2 > weakly
basic anion exchangers.
– Dye sorption kinetics is affected by matrix structure of ion exchangers; in the
case of dye sorption on the gel resins, the sieve effect consists in limited diffusion
of large-size dye ions in the pores of the resin of microporous structure.
– The main binding mechanism of dyes is ion-exchange reaction; physical and
hydrophobic π–π interactions (among benzene rings in dyestuff and resins
matrix) play a more significant role in case of the polyacrylic anion exchangers
such as Amberlite IRA 958, Amberlite IRA 458, and Amberlite IRA 67 in comparison to polystyrene ones; large sorption ability of anion exchangers resins
toward dyes results from H-bond formation (nitrogen from quaternary ammonium and oxygen from carbonyl functional groups of anion exchangers interact
with nitrogen from the -NH 2 group of dyes).
– A lack of evident impact of solution pH on dye uptake indicates that the process
of their bonding on the resin proceeds not only by ion pair formation between the
sulfonic groups of dyes and tertiary amine groups of the weakly basic anion
exchangers or the quaternary ammonium functionalities of strong base anion
exchange resins but also by the interactions of π–π type as well as hydrogen bonds.
– Kind of dye (composition and spatial structure, number and kind of chromophore, and auxochromium).
– Process conditions (kind of the dye-ion exchanger system, concentration of the
dye, phase contact time, presence of auxiliaries in the system, e.g., electrolytes
and surfactants, solution pH, temperature, rate of phases mixing or rate of flow
in the column system, desorption, as well as way of its conducting (static or
dynamic method) (Wawrzkiewicz and Hubicki 2015).
A. Wołowicz and M. Wawrzkiewicz