Preparation And Properties Of Soil-based Polymer Anti-evaporation Composite Materials

China is a country with a large population,and the demand for food is enormous.However,the fact that there are more people and less land is the basic national condition of our country.The area of sandy land accounts for 2.6 billion mu,but the arable land is less than 2 billion mu in China,and the available cultivated land is decreased year by year.Therefore,the development and utilization of sandy land is of great significance for solving the shortage of cultivated land in our country.Most of the sandy land is located in arid and semi-arid areas and desertification areas,with less precipitation and large evaporation,so,the biggest obstacle to the development and utilization of sandy land is the problem of drought and water shortage.In areas with less precipitation,the greater the proportion of evaporation in water loss.The use of some polymer materials in arid areas can not only reduce the evaporation rate of soil water and improve soil moisture,but also effectively prevent soil erosion,improve soil ecological function and provide good soil and water conditions for plant growth.In this paper,used loess and clay which are abundant in nature as basic materials,added natural polymer materials or composite absorbent materials,and prepared soil-based polymer anti-evaporation composite materials.Its anti-evaporation performance was investigated under natural conditions.The contents are as follows:1.The soil-based polymer anti-evaporation composite materials were prepared by multi-site in-situ polycondensation using loess and laterite and biomass straw as raw materials,adding different content of plant gum(starch,gelatinized starch,cellulose).The structure and morphology of the material were characterized by FTIR,SEM and solid particle size analysis.The effects of polymer types and contents on the evaporation properties of soil-base materials were investigated under natural conditions.The results showed that the soil-based anti-evaporation composite materials prepared by adding gelatinized starch of different contents had excellent anti-evaporation performance.The composite material with 6.00% gelatinized soluble starch,evaporation can be reduced by 44.65% within 125.5 h.Most of the soil-based composites prepared by adding plant gum had good anti-evaporation properties,and the evaporation of the composites with 1.00% xanthan gum can be reduced by 31.54% within 74.5 h.The soil-based anti-evaporation composite material prepared by adding different content of cellulose had better performance,and the evaporation composites with 1.00% and 2.00% carboxymethyl cellulose sodium(300-800 mPa·s)can be reduced by 35.75% and 41.71%,respectively within 70.5 h;and the evaporation of the composites with 1.00% and 2.00% hydroxymethyl cellulose sodium(600-3000 mPa·s)can be reduced by 34.24% and 43.00%,respectively within 76.0 h.2.To study the application of composite absorbent material in preventing water evaporation in soil,hydroxymethyl cellulose sodium-g-poly(acrylic acid-co-2-acrylamido-2-methyl-1-propanesulfonic acid)/laterite(NaHMC-g-P(AA-co-AMPS)/ laterite)composite absorbent material 1(CAM1)was prepared by radical polymerization.The structure and morphology of CAM1 were characterized by FTIR,SEM and TGA,reaction conditions was optimized and the factors affecting the water absorbency of CAM1 were studied.The water absorption of the CAM1 under the optimum synthetic conditions reached the equilibrium at 15 min in distilled water,and the optimum water absorption of CAM1 was 1329 g/g,269 g/g and 140 g/g in distilled water,tap water and 0.9 wt% NaCl solution,respectively.The swelling kinetic mechanism of the CAM1 was explained by the pseudo-second-order swelling kinetics model and Ritger-Peppas model.The effects of soil type,particle size and content of CAM1 on water evaporation rate in soil were studied.3.Hydroxypropyl cellulose-g-poly(acrylicacid-co-2-acrylamido-2-methyl-1-propane sulfonic acid)/laterite(HPC-g-P(AA-co-AMPS)/laterite)composite absorbent material 2(CAM2)was prepared by freeradical polymerization.The structure and morphology of the synthetic materials CAM2 were characterized by FTIR,SEM and TGA.The fluid absorbency of CAM2 in different salt solutions was investigated,and it was proved that the CAM2 was more sensitive to salt solutions.The water absorbency rate of the resin in distilled water was fast,and the water absorption equilibrium is achieved at 18 min.The optimum water absorbency in distilled water,tap water and 0.9 wt% NaCl solution were 1427 g/g,272 g/g and 143 g/g,respectively.The swelling kinetic mechanism of CAM2 was explained by pseudo-second-order swelling kinetic model.Its water retention performance was good at different temperatures and speeds.The effects of the content of CAM2 on soil water evaporation and shrinkage of soil crust were studied.4.Hydroxyethyl cellulose-g-poly(acrylic acid-co-2-acrylamide-2-methyl-1-propane sulfonic acid)/laterite(HEC-g-P(AA-co-AMPS)/laterite)composite absorbent material 3(CAM3)was prepared by aqueous solution polymerization.The structure and morphology of the composite materials were characterized by FTIR,SEM and TG/DTG.The optimal water absorbency of CAM3 in distilled water,tap water and 0.9 wt% NaCl solution were 1294 g/g,177 g/g and 119 g/g,respectively.The water retention performance and re-swelling property of CAM3 at different temperatures were studied,and these performances were good.The water absorption rate of CAM3 in distilled water was very fast,and the swelling equilibrium was reached at 5 min.The swelling mechanism of CAM3 was explained by the pseudo-second-order swelling kinetics model and Ritger-Peppas model.The effect of the amount of hydrogel on the water evaporation rate in soil was investigated.