Controlled release characteristics of methylenebisacrylamide crosslinked superabsorbent polymer for water and fertilizer conservation in agriculture sector

A series of superabsorbent polymers (SAPs) were synthesized free-radically using hydroxyethyl methacrylate (HEMA), acrylic acid (AA) and its potassium salt, methacrylic acid (MAA) and its potassium salt as monomers, and N,N'-Methylenebisacrylamide (N,N 1 -MBA) as crosslinker. The synthesized SAPs were evaluated for their chemical structure (FT-IR), thermal stability (TGA/DTG), surface morphology (SEM), and water, fertilizers uptake and release characteristics (swelling and deswelling). A SAP with the optimized composition of monomer and crosslinker had absorbed 898 g/g of water, and 68% of urea and 51% of potash from the 1% corresponding fertilizer solutions. The equilibrium swollen SAP had released the absorbed water completely over 21 days, but only 28% of potash and 43% of urea were released from the fertilizer-loaded SAPs under identical conditions with the same duration of release time. The water uptake followed Fickian diffusion mechanism for the optimized SAP. Thus obtained experimental results revealed that the synthesized SAP may be used as the matrix for the controlled release of water and fertilizers in the agricultural sector.