Study On Preparation And Properties Of Functional Composite Super Absorbent Resin

Drought and water shortage seriously constrain the development of China's economy and society.The high water-absorbing resin itself is a three-dimensional network structure with a certain degree of cross-linking.It can quickly absorb water that is hundreds or even thousands of times greater than its own weight.It is widely used in all walks of life,especially in agriculture.In this paper,sodium carboxymethyl cellulose?CMC?was used as raw material,potassiumpersulfate?KSB?wasusedastheinitiator,and N,N'-methylenebisacrylamide?MBA?was used as the crosslinking agent.The above materials were graft-copolymerized with acrylic acid?AA?by aqueous solution polymerization,and the optimum conditions were determined by single-factor experiments.The cellulose-based superabsorbent resin CMC-AA with good degradation performance was synthesized.On this basis,potassium hydroxide and urea were introduced into the reaction system to prepare functional composite water-absorbing resins K-CMC-AA and UREA-CMC-AA,respectively.The microstructures of the resin products were characterized by scanning electron microscope?SEM?,Fourier transform infrared spectroscopy?FTIR?and differential scanning calorimetry?DSC?.The water absorption properties of the above three resin products in different swelling media were investigated,and the water absorption process was fitted using the kinetic model.The adsorption process and mechanism were discussed.Through laboratory simulation experiments,UREA-CMC-AA was initially applied to the soil,and its preliminary application effects and degradation performance in soil were discussed.The details are as follows:1.The optimal conditions for the synthesis of CMC-AA were as follows:40 mL of acrylic acid,neutralization with NaOH,neutralization degree of 80%,CMC 4.5 g,KSB 0.16 g,MBA 0.02 g,and reaction temperature of 75°C.Potassium hydroxide was used to neutralize part of AA.When the KOH neutralization ratio was 10%,the water absorption ratio of K-CMC-AA in 0.1%NaCl was 285.06 g/g,which was about 80%higher than that of CMC-AA.Urea was added to the reaction system by chemical synthesis.When the mass ratio of urea to CMC was 1:1,the absorbency of the obtained product,UREA-CMC-AA,was 358.94 g/g,148.58 g/g and 34.08 g/g in H₂O,0.1%NaCl,and 0.1%CaCl_2,respectively.2.The water absorption kinetics of three resin products in distilled water or salt solution can be described by the second-order kinetic equation.The external solution has a great influence on the water-absorbing performance of the resin product.K-CMC-AA has strong salt tolerance and low sensitivity to external salt solution concentration.Its inhibition by salt solution is less than UREA-CMC-AA,CMC.-AA.When the pH of the solution is equal to 8,the three kinds of resin products have the highest water absorption rates,which are 402.09 g/g,397.62 g/g,and404.73 g/g,respectively,and the acidic condition has a more pronounced inhibitory effect on the water absorption of the superabsorbent polymer.The effect of different metal ions on the water absorption capacity of the three resin products is Ca²⁺>Mg²⁺>K⁺>Na⁺.The water absorption capacity of three kinds of superabsorbent resin products when they reached equilibrium in salt solution decreased with the increase of ionic strength.After repeated aspiration of the three resin products for five times,the water absorption ratios were respectively 57.4%,52.5%,and 54.3%of the initial water absorption ratio,and the water-absorbing resin product had better repeated use performance.3.UREA-CMC-AA exhibited better sustained-release properties.Applying it to soil significantly improved the water holding capacity of the soil.UREA-CMC-AA has a certain loosening effect on the soil,improving the soil pore status and increasing the permeability of the soil.With a 1%high water-absorbent resin application volume,the soil bulk density is lower than that of the soil without water-absorbent resin.The application of high water-absorbing resin products had little effect on soil pH and conductivity.UREA-CMC-AA increases soil organic matter content.When UREA-CMC-AA was buried in soil for 42 days,the degradation rate was 63.70%,showing good biodegradability.