Synthesis, chracterization and swelling behavior of a poly(acrylamide-co-acrylic acid) copolymer: Application to water retention in two sandy agricultural soils in sub-Saharan region.

The application of copolymer hydrogels based on acrylamide (AAm) and acrylic acid (AA) in sub-Saharan soils can increase the quantity of water retained by the soil and improve plant establishment and growth. The aim of this work was to synthesize and characterize a copolymer based on acrylamide and acrylic acid and to evaluate its swelling capacity with different physicochemical parameters. This study also aimed to investigate the effect of metallic cations on the swelling capacity of the copolymer and to assess the improvement in water retention in sandy soils. The copolymer material was prepared by free-radical polymerization in aqueous solution at a temperature of 60 C and characterized by Fourier transform infrared (FTIR) and x-ray diffraction (XRD), and its average molecular weight was estimated from intrinsic viscosity measurements. The swelling capacity was evaluated with different physicochemical parameters, and the effect of metallic cations on the swelling capacity was investigated. Water retention in two sandy soils was also evaluated. The copolymer material containing 50% AAm and 50% AA can retain more than 8100% of water. The swelling ratio increased with increasing temperature, with a maximum swelling ratio at 65 C. The presence of metallic cations reduced the maximum swelling ratio of the copolymer material as the cation concentration increased. The copolymer material at 1% in a composition with the soil showed an improvement in the water retention of 12.2% and 7.9% for soil A and 7.9% for soil B. Soil air volume is improved by 19% for both soils. This study shows that the copolymer material has a high swelling ratio and can improve water retention in sandy soils. The copolymer can be used in agriculture to protect and improve plant growth and yield.