Polyacrylamide Soil Conditioners: The Impact …
117
Currently, many studies refer to the assessment of mineral particle stability in
colloidal systems, the nature of interactions between them, as well as the impact
of high molecular compound presence on the suspension stability. These studies
mainly refer to polyacrylamide (PAM) which is a non-toxic, environmentally friendly
polymer that has the ability to stabilize and improve soil structure [69, 70]. Its beneficial effect is related to maintaining or increasing soil aggregation and pore continuity
[71–73], increasing aggregate stability, and thus soil structural stability [74, 75]. The
potential benefits of using PAM are influenced by a number of relationships between
the properties of the polymer (its molecular weight, type, amount of surface charge,
conformation of macromolecules, and density of the charge) and the properties of
the soil (its type, texture, organic matter and clay mineral content, ionic strength,
pH value, composition, and ion concentration in soil solution) [1, 76–79]. The type
of polymer (and thus charge present in macromolecules) affects the amount of its
adsorption on solid surface. The polymer adsorption increases with the following
order: anionic PAM < nonionic PAM < cationic PAM [1]. Nonionic polyacrylamide
adsorption on clay minerals is mainly caused by van der Waals forces [80], whereas
cationic or anionic forms adsorb and bind soil particles through electrostatic forces
or bridge formation between PAM charged moieties and solid surface group [1, 80].
Malik and Letey [81] concluded that due to differences in polymer chain conformations influenced by ionic PAM hydrolysis degree the stabilization of soil by polyacrylamide can vary. Adsorbed polymeric chain conformation results from solution
pH value and surface charge. The higher the percent of hydrolysis (greater amount of
positively or negatively charged groups) was, the more linear, well-developed macromolecular chain and more extended conformation was obtained, and thus greater
adsorption was observed [81, 82]. Adsorption of PAM characterized by 2 and 20%
hydrolysis degree was studied [83]. The adsorption of polymer with greater amount
of hydrolyzed groups was higher, whereas the more significant stability of soil aggregates with PAM 2% was observed. Several papers related to the effect of electrolyte
present on polymer adsorption and its ability to soil stabilizing. The electrolyte presence in adsorption system enhances the effectiveness of soil aggregate stabilization
by polymer and its adsorption on mineral surface [83].
The addition of polymer to the soil stabilizes existing aggregates and strengthens
the mutual binding of adjacent particles. The stabilizing efficiency of polyacrylamide
is mainly determined by the adsorption of its macromolecules on the surface of soil
particles [84]. The aggregate formation contributes to several beneficial phenomena
such as stability increase, reinforcement of soil structure, water infiltration promotion
as well as erosion limitation [86]. Shainberg et al. [85] and Ben-Hur et al. [86]
conducted infiltration studies with polyacrylamide and soils rich in clay mineral
fractions. Application of PAM flocculant promotes surface sealing prevention which
results in greater infiltration rate. Fox and Bryan [87], Stern et al. [68], and Smith
et al. [88] determined the influence of PAM presence on soil erosion and field runoff
reduction. Soils treated with polyacrylamide maintain their original physical state
in water erosion conditions. By stabilization of clay mineral aggregates by polymer
adsorption, the water infiltration rate improvement and soil erosion reduction are
observed.
117
Currently, many studies refer to the assessment of mineral particle stability in
colloidal systems, the nature of interactions between them, as well as the impact
of high molecular compound presence on the suspension stability. These studies
mainly refer to polyacrylamide (PAM) which is a non-toxic, environmentally friendly
polymer that has the ability to stabilize and improve soil structure [69, 70]. Its beneficial effect is related to maintaining or increasing soil aggregation and pore continuity
[71–73], increasing aggregate stability, and thus soil structural stability [74, 75]. The
potential benefits of using PAM are influenced by a number of relationships between
the properties of the polymer (its molecular weight, type, amount of surface charge,
conformation of macromolecules, and density of the charge) and the properties of
the soil (its type, texture, organic matter and clay mineral content, ionic strength,
pH value, composition, and ion concentration in soil solution) [1, 76–79]. The type
of polymer (and thus charge present in macromolecules) affects the amount of its
adsorption on solid surface. The polymer adsorption increases with the following
order: anionic PAM < nonionic PAM < cationic PAM [1]. Nonionic polyacrylamide
adsorption on clay minerals is mainly caused by van der Waals forces [80], whereas
cationic or anionic forms adsorb and bind soil particles through electrostatic forces
or bridge formation between PAM charged moieties and solid surface group [1, 80].
Malik and Letey [81] concluded that due to differences in polymer chain conformations influenced by ionic PAM hydrolysis degree the stabilization of soil by polyacrylamide can vary. Adsorbed polymeric chain conformation results from solution
pH value and surface charge. The higher the percent of hydrolysis (greater amount of
positively or negatively charged groups) was, the more linear, well-developed macromolecular chain and more extended conformation was obtained, and thus greater
adsorption was observed [81, 82]. Adsorption of PAM characterized by 2 and 20%
hydrolysis degree was studied [83]. The adsorption of polymer with greater amount
of hydrolyzed groups was higher, whereas the more significant stability of soil aggregates with PAM 2% was observed. Several papers related to the effect of electrolyte
present on polymer adsorption and its ability to soil stabilizing. The electrolyte presence in adsorption system enhances the effectiveness of soil aggregate stabilization
by polymer and its adsorption on mineral surface [83].
The addition of polymer to the soil stabilizes existing aggregates and strengthens
the mutual binding of adjacent particles. The stabilizing efficiency of polyacrylamide
is mainly determined by the adsorption of its macromolecules on the surface of soil
particles [84]. The aggregate formation contributes to several beneficial phenomena
such as stability increase, reinforcement of soil structure, water infiltration promotion
as well as erosion limitation [86]. Shainberg et al. [85] and Ben-Hur et al. [86]
conducted infiltration studies with polyacrylamide and soils rich in clay mineral
fractions. Application of PAM flocculant promotes surface sealing prevention which
results in greater infiltration rate. Fox and Bryan [87], Stern et al. [68], and Smith
et al. [88] determined the influence of PAM presence on soil erosion and field runoff
reduction. Soils treated with polyacrylamide maintain their original physical state
in water erosion conditions. By stabilization of clay mineral aggregates by polymer
adsorption, the water infiltration rate improvement and soil erosion reduction are
observed.