Ultraviolet-induced Polymerization And Properties Of Superabsorbent Composites Based On Acrylic Acid And Humic Acid

As a functional polymer materials with high water absorption and high water retention ability,superabsorbent can be applied in agriculture and forestry horticulture,health supplies,building materials,waste water treatment and coal dehydration and other fields.At present,polyacrylic acid based superabsorbent polymer is the most widely used resin in the world,which has the advantages of good water absorption and simple preparation method.There are also disadvantages of them due to their dependence on the high cost petroleum products and their poor biodegradability,which limits their applications in many aspects.Humic acid is a rich source of natural highmolecular polymer with excellent degradation,reproducibility,promoting plant growth properties.For the needs of lower cost and perfection of structure and functions of resin,a lot of HA were introduced into the polymer crosslinking network.UV-initiated polymerization is a kind of environment-friendly green technology with simple process,fast curing speed,high energy utilization rate,no waste pollution and excellent curing product performance.This paper takes UV-initiated polymerization and the introduction of large number of HA as its focus,concentrating on the four key areas of work:1)Polyacrylic acid/sodium humate(PAA/SH)superabsorbent composites were synthesized by using acrylic acid and sodium humate as raw materials.When the mass fraction of SH was 10%,20%,30% and 40%,respectively,ammonium persulfate(APS)as the thermal initiator and 2,2-dimethoxy-phenyl ketone(BDK)as the photo initiator,N,N-methylenebisacrylamide(MBA)as cross-linker,a series of SH-based superabsorbent composites was synthesized.Under the optimum conditions,the water absorption rates were 1844 g/g,1425 g/g,1053 g/g and 827 g/g,respectively.The resin was characterized by infrared spectroscopy(IR),thermogravimetric analysis(TGA)and scanning electron microscopy(SEM).The resin has good water absorption reversibility,soil water holding and degradability capacity.We also synthesized a coated controlled-release fertilizer employing PAA/SH-20,which can effectively retard the release rate of urea in the soil.2)We change sodium humate for humic acid,which simplifies the experimental procedures,reducing the risk of soil sodium damage.When the mass fraction of HA was 50%,60%,70% and 80%,APS and BDK as synergistic initiators,MBA as the cross-linker,sodium lauryl sulfate(SDS)and polyvinylpyrrolidone(PVP)was prepared as a compounded dispersant,a series of humic acid-based superabsorbent composite were synthesized.Under the optimum conditions,the water absorption rates of them were 783 g/g,523 g/g,467 g/g and 423 g/g,respectively.3)In order to increase the water solubility,dispersibility and salt resistance of humic acid,humic acid was modified into sulfomethylation humic acid(SHA).The optimum sulfomethylation conditions for humic acid were determined by orthogonal test and conductivity determination.When the mass ratio of SHA was 60%,APS and BDK as synergistic initiators,MBA as the cross-linker,PAA/SHA-60 were synthesized.And the resin with SHA content of 50%,70% and 80% was synthesized under the optimum synthesis conditions.The resulting composites has a lower water absorption rates compared to the products in Chapter 3,but has a slight increase in salt tolerance.4)The effects of the addition amount of product PAA/SH-20 prepared in the second chapter on the germination rate and plant height of turf grass Sijiqing were analyzed.The results showed that the application of PAA/SH-20 could effectively promote the germination and growth of Sijiqing,which also could improve water use efficiency.