Synthesis and properties of agricultural hydrogels based on carboxymethylcellulose, urea, bentonite, and kaolin

In this study, a highly swellable composite hydrogel based on carboxymethyl cellulose, methacrylic acid, bentonite, kaolin, and urea was synthesized for agricultural application.The hydrogel was prepared in an aqueous medium using radical grafting and cross-linking techniques.During synthesis, carboxymethyl cellulose served as the polymer matrix, methacrylic acid as the monomer, ammonium persulfate as the initiator, and N,N′-methylenebisacrylamide as the crosslinking agent.The structure and physicochemical properties of the resulting hydrogel were investigated using IR spectroscopy, thermogravimetric and differential thermal analysis, and X-ray diffraction methods.The results indicated the formation of a three-dimensional polymer-mineral network within the hydrogel.The water absorption capacity of the hydrogel was significantly dependent on the pH of the medium, reaching a maximum value of 420 g/g at pH 7. It was observed that water absorption capacity decreased as the salt concentration increased in NaCl, CaCl 2 , and AlCl 3 solutions.During repeated swelling-drying cycles, the hydrogel retained its effective properties for the first 4-5 cycles.Furthermore, the release of urea incorporated into the composite was significantly slower compared to ordinary urea, reaching 89.5 % over a period of 30 days.The results indicate that this hydrogel is a promising material for retaining soil moisture and ensuring the controlled release of nitrogen fertilizers.значительно замедлилось по сравнению с простой мочевиной, достигнув 89,5 % в течение 30 дней.Полученные результаты указывают на то, что этот гидрогель является перспективным материалом для поддержания влажности почвы и обеспечения контролируемого высвобождения азотных удобрений.