Thermodynamic evaluation of the impact of strongly swelling polymer hydrogels with ionic silver on the water retention capacity of sandy substrate

The impact of two types of strongly swelling polymer hydrogel (SSPH) on the water retention capacity of quartz sand in pure water and Ag⁺ solutions (10-100 mg/l) has been studied by using a centrifugation method in a wide range of thermodynamic water potential (Gibbs energy) from 0 to 3030 J/kg. The experimental data for the water retention curves (WRC) were estimated by the van Genuchten model. Both hydrogels – the Aquasorb preparation (Germany) with hydrophilic properties and high degree of swelling in pure water (700–1000 g H₂O/g) and the new Russian amphiphilic SSPH with a peat filler (degree of swelling 500-700 g H₂O/g) were very effective as water adsorbing soil conditioners in relatively small doses from 0.05 to 0.3% per mass of dry (105°C) soil substrate. The water retention capacity of sandy substrate increases under the influence of SSPH with 2-3 times up to the level of native loamy sands and loams. Adding Ag⁺ to the water solution results just for the highest concentration of SSPH (0.3%) and iconic silver (100 mg/l) in a significant decrease of the water retention in the soil-gel compositions. (paper)