Synthesis and application of super absorbent polymers synthesized with ammonia solution and diatomaceous earth with low toxic residues

Water-soluble harmful components that remained in SAPs pose potential risks to crop growth, resulting in decreased seed germination rate, reduced yield, and inhibited root system growth. These factors restrict its widespread use in agriculture and forestry. In this study, a new type of super absorbent polymers (AD-SAP) with low residual acrylic acid and sodium ions was synthesized by using ammonia solution instead of strong alkali sodium hydroxide for neutralization and adding modified diatomaceous earth to improve the grafting efficiency. The prepared samples were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS), and the influence of the dosage of acrylic acid and ammonia solution used for preparation on the residual content of water-soluble harmful components in AD-SAPs was investigated. When 28% of acrylic acid, 24% of ammonia solution, and 5% of diatomaceous earth were used for synthesis, the residual acrylic acid content in AD-SAP was 0.03%, and the sodium ion content was reduced to 0.12 g/kg, which is much lower than the three commercially available SAPs. However, its water-absorption capacity has not decreased and its salt resistance has improved. The water absorption ratio of AD-SAP is 578g/g, and the salt-absorption ratio is 87 g/g. Pot experiments showed that AD-SAP eliminated the adverse effects of commercial SAPs on crop growth. The research provided technical support for the production of SAPs, and offer scientific guidance for how to mitigate the adverse effects of SAPs on crop growth.