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The review discusses the application of polymers for the control of soil degradation caused by wind and water erosion. The background of the problem, current situation with the soil erosion in the world and Russian Federation, traditional methods for controlling erosion processes, and natural and synthetic soil amendments (soil conditioners) are described. Particular attention is paid to t traditional conditioners, polyacrylamide and its derivatives as well as conditioners obtained from interpolyelectrolyte complexes, the products of interaction of oppositely charged ionic polymers. The results of the laboratory experiments, field tests, and practical application of the conditioners are presented. A new type of soil conditioners based on interpolyelectrolyte complexes is described in detail, and the prospects of their application in antierosion technologies are considered.

Interpolyelectrolyte complexes of a linear cationic polymer poly(diallyldimethylammonium chloride) and anionic microgel particles with carboxyl groups in a pH 6 buffer solution are presented. Dispersions of the microgel and its complexes—negatively charged with a 3-fold molar excess of the anionic groups of the microgel and positively charged with a 3-fold molar excess of the cationic groups of the polycation—retain aggregative stability for six months. When applying 1 wt % dispersions of the microgel and complex on the surface of the soil with a high sand content, polymer-soil coatings with a mechanical strength of 19 to 61 kg/m2 depending on the composition of the dispersion are formed. These indicators significantly exceed those for coatings obtained by applying a 1 wt % solution of a linear anionic polymer, poly(acrylic acid), on the soil surface. Coatings involving microgel and its complexes remain stable at an air flow rate of 190 km/h.

The initial-stage dynamics of flocculation of positively charged latex particles induced by polyelectrolytes (PEs) and polyelectrolyte complexes (PECs), composed of linear polyacrylic acid (PAA) and a PAA-based hydrophilic microgel (PAA#) with a small amount of a linear polycation, was comparatively analyzed by applying the standardized colloidal mixing procedure. Based on the rate of flocculation, this method allows us to investigate the dynamics of flocculation immediately after the onset. In addition to confirming the prediction made regarding the initial rate of flocculation with linear polyanions-which was mostly similar to that observed in negatively charged colloids with positively charged PEs-we have confirmed two important new results regarding the microgel: (1) the increase of the initial rate is less markedly affected by the microgel concentration than by the linear polymer concentration, which can be explained by the fact that the three-dimensional (3D) cross-linked structure of the microgel that does not deform as easily as the linear structure upon touching the colloidal surface; and (2) there is a remarkable increase of the initial rate due to the contribution of instant aggregation of the negatively charged microgel induced by the polycation adsorption. These results suggest the significance of state and formation dynamics of PECs prior to reaching the surface of targeted colloidal particles for the intension of effective flocculation. These aspects are not treated so far in the dynamic process of flocculation.

The preparation of electrostatic complexes between a cationic polymer, poly(diallyldimethylammonium chloride), and natural polyanions, potassium humates, is described. The polycomplexes remain stable in the aqueous solution for a long time (up to 3 months) or form precipitates that can be easily resuspended when the sample is shaken. When aqueous solutions/suspensions of polycomplexes are applied on the sand surface, polymer-sand coatings (crusts) are formed, the mechanical strength of which increases with increasing content of poly(diallyldimethylammonium chloride) in the polycomplex. The greatest resistance to water (water resistance) is exhibited by crusts with a high proportion of mutually neutralized sections of both polymers. For such crusts, sand loss during watering is in the range from 0 to 2%. The developed multicomplex formulations can be used to stabilize soil and ground against water and wind erosion.

In this article we describe the use of novel aqueous polymer formulations for stabilization of sand and soil against wind erosion and retention of water in polymer-treated sand/soil samples. Two series of formulations were prepared. The first consisted of polyacrylic acid (PAA) and two electrostatic complexes of PAA with cationic poly(diallyldimethylammonium chloride): negatively and positively charge; the second included PAA-based cross-linked copolymer (PAA#) which forms microgel particles upon swelling and two its electrostatic complexes with the polycation: negatively and positively charged. 1 mass% formulations showed the stability against aggregation for 3 months excepting the negative complex with PAA which aggregated within half an hour after preparation. The viscosity of 1 mass% formulations, which lies within a (1.6÷320)×10−6 m2/s interval, allowed their deposition over fine-grained sand and loamy sand soil using a conventional spray machine followed by formation of polymer-sand(soil) crusts. Both for sand and soil, the PAA#-based crusts demonstrated a higher resistance to mxechanical loads in comparison with the crusts formed by linear PAA: up to a 42.5 MPa mechanical strength for sand/PAA# crust against a 12.5 MPa strength for sand/PAA crust. Additionally, the PAA#-based crusts was not impacted by airstream, up to a 190 km per hour air speed, while PAA-based crust was destroyed within a minute. Finally, PAA# alone and its negative complex were characterized by a high swelling (degree of swelling up to 195) that allowed them to maintain a high water retention capacity, being bound to sand and soil. The results are promising for preparing anti-erosion and water-saving formulations, especially in areas with insufficient moisture content, and design of sand-based composite materials.

Soil erosion is a global problem with grave social, economic and ecological consequences. To stabilize the top soil layer, various approaches have been developed, including the use of synthetic and natural water-soluble polymers capable of binding to soil particles and forming a protective layer (crust) on the topsoil. Individual water-soluble polymers give crusts which lose mechanical stability after re-watering. We describe in the article effective stabilizers of model unstructured soil, sand, “polyelectrolyte complexes” (PECs), composed of two oppositely charged ionic polymers (polyelectrolytes), cationic poly(diallyldimethylammonium chloride) (PDADMAC) and anionic potassium humates (PH). By varying the PDADMAC-to-PH ratio, the total charge of PECs and their solubility in water was adjusted. The PECs as well as PDADMAC and PH were deposited on the surface of monomineral quartz sand, with a mean diameter of particles from 0.15 up to 2.1 mm. After drying, polymer-sand crusts were formed; their mechanical strength increased upon elevating the cationic content in the polymer formulation. Re-watering caused both polyelectrolytes and PECs with a great excess of cationic or anionic groups to be removed from the crusts, which was additionally accompanied by loss of sand and decrease in the mechanical strength of the crust. The slightly positive PECs with a significant degree of mutually neutralized charges (“hydrophobized” blocks) formed the most stable crusts due to electrostatic and hydrophobic contacts with sand particles. A correlation was thus revealed between the PEC composition and the anti-erosion resistance of the polymer-sand crusts. It is shown that the use of non-stoichiometric polycomplexes makes it possible to manipulate the mechanical strength of the resulting coatings. The described approach is promising for fabrication of polymer formulations for environmental protection, conservation/rehabilitation of landfill sites, desertification control, anti-erosion treatment of agricultural land, conservation of mining dumps, treatment of road slopes, etc.