Synthesis of a novel superabsorbent with slow-release urea fertilizer using modified cellulose as a grafting agent and flexible copolymer

In this work, a number of glucose unites in polymeric structure of cellulose was converted to 2,4-dihydroxy-3-(1-hydroxy-2-oxoethoxy)butanal (cellulose containing di aldehyde units (CCDAUs)) by oxidation with sodium periodate, followed by condensation with acetone to produce 5,7-dihydroxy-6-((1-hydroxy-4-oxopent-2-en-1-yl)oxy)hept-3-en-2-one unites (cellulose containing di ene units (CCDEUs)). This modified cellulose was characterized by different methods and applied as a copolymer and grafting agent to synthesize an eco-friendly (CCDEUs-g-poly(AA)/urea) superabsorbent with slow-release urea fertilizer. The created double bonds in C2 and C3 positions of β-d-glucose units increased the linkage between cellulose and acrylic acid, leading to the formation of a strong network for slow-release urea fertilizer. Also, this modification created an expanded network for storage a high amount of water by increasing the cellulose flexibility. The reaction conditions for modification and synthesis of the superabsorbent, the oxidation degree value of glucose units, kinetics models, the effect of different saline solutions, various pH and reswelling time on the water absorbency, water retention capacity, reusability, biodegradability, and slow-release property were investigated. Also, the effect of synthesized CCDEUs-g-poly(AA)/urea on plant growth was tested and excellent results were obtained.