| Super-absorbent polymer(SAP),as a polymer material with three-dimensional network pore structure,is mainly synthesized by the polymerization of polyacrylic acid.It is widely used in hygiene,food,medical treatment,slow emancipation,catalysis,sensing,and sewage processing,blocking and waterproofing,construction and gardening and other fields.In recent years,the preparation of super-absorbent polymer by grafted modification of natural cellulose has become a research hotspot,and has been used as water retention,fertilizer slow-release,and pesticide adsorbents,etc.in the field of agriculture and forestry to improve soil quality,increase fertilizer efficiency and soil water retention.The natural cellulose-based super-absorbent polymer structure contains biomass cellulose,which not only has the water retention properties the same as the general super-absorbent polymer,but also may have a certain influence on the seed germination process.Therefore,studying the effect of natural cellulose-based super-absorbent polymer on the germination rate and germination time of agricultural seeds has important application value.9 kinds of corn stover cellulose-based super-absorbent polymers were prepared by abundant agricultural by-product corn stalk as cellulose source,acrylic acid(AA)as the main hydrophilic monomer,combined with 2-acrylamido-2 methyl propanesulfonic acid(AMPS),acrylamide(AM),itaconic acid(IA)as assisted hydrophilic monomers and montmorillonite(MMT).The effects of four of the super-absorbent polymers on the germination time and germination rate of Chinese cabbage seeds were evaluated.The main research contents include:(1)Homemade corn stalk cellulose as a raw material was etherified to synthesis sodium carboxymethyl cellulose(CS-CMC,CMC).CS-CMC(main chain),hydrophilic monomer AA(branched chain),potassium persulfate(KPS,initiator agent)and N,N'-methylenebisacrylamide(MBA,crosslinking agent)were dissolved in distilled water,acrylic acid grafted corn stalk cellulose based super absorbent polymers(CS-AA)were prepared by aqueous solution polymerization method.When the amount of CS-CMC was1.00 g,the amount of AA was 7.00 g and the degree of neutrality was 70 %,the amount of KPS was 0.063 g,and the amount of MBA was 0.014 g,the largest Qw of the prepared CS-AA is 620.29 g/g.The salt water absorption rate Qs value of CS-AA was 89.72 g/g.The water retention rate is still 51.60 % under the condition of 55 ? and 10 h.The structure of CS-AA was analyzed by Fourier infrared spectroscopy(FT-IR),the micro morphology of CS-AA was analyzed by scanning electron microscopy(SEM),and the thermal performance analysis of CS-AA was studied by thermal gravity analysis technology.The experiment of breeding Chinese cabbage on CS-AA showed that CS-AA can shorten the first germination time of seeds to 11 d,increase the germination rate to 60%and increase the average growth height of seeds to 6.37 cm.(2)CMC was used as main chain,AA was combined with 2-acrylamido-2 methyl propanesulfonic acid(AMPS),acrylamide(AM)and itaconic acid(IA)to form a mixed hydrophilic monomers as branched chains,KPS was used as initiator agent and MBA was used as crosslinking agent to prepare three double hydrophilic monomers grafted corn stalk cellulose-based super-absorbent polymers under a certain degree of neutrality,which were named as 2-acrylamido-2-methylpropanesulfonic acid modified acrylic acid grafted corn stalk cellulose-based super absorbent polymers(CS-AAMPS),acrylamide modified acrylic acid grafted corn stalk cellulose-based super absorbent polymers(CS-AAM)and itaconic acid modified acrylic acid grafted corn stalk cellulose-based super absorbent polymers(CS-AIA),respectively.The influence of hydrophilic monomer quality,neutrality degree,initiator dosage and crosslinking agent dosage on their Qw and Qs was discussed.The experimental results showed that when CS-CMC was 1.00 g,when the dosage of AA was 7.00 g,AMPS was 2.00 g,the neutrality degree of AA and AMPS were 70 %,the dosage of KPS was 0.063 g,and the dosage of MBA was 0.014 g,the Qw and Qs of CS-AAMPS were relatively larger,which were 860.03 g/g and 67.74 g/g,respectively;When CS-CMC was 1.00 g,AA dosage was 7.00 g,AM was 1.00 g,AA neutrality degree was 70 %,KPS dosage was 0.063 g,and MBA dosage was 0.014 g,the Qw and Qs of CS-AAM were relatively larger,which were606.23 g/g and 90.21 g/g,respectively;Under the conditions of 1.00 g CS-CMC,6.00 g AA,1.00 g IA,AA neutrality degree 70 %,IA neutrality degree 87 %,0.070 g KPS,0.070 g MBA conditions,CS-AIA was prepared,and the Qw and Qs were respectively larger,which were288.33 g/g and 50.63 g/g,soil degradation can reach 39 % in 15 days.The composition was analyzed by FT-IR and XPS,and the microscopic morphology was analyzed by SEM.(3)CMC was used as main chain,AA was combined with AMPS,AM to form a mixed hydrophilic monomers as branched chains,KPS was used as initiator agent and MBA was used as crosslinking agent to prepare a tri-hydrophilic monomers grafted modified corn stalk cellulose-based super absorbent polymer(CS-AAA)under a certain degree of neutrality.The experimental results showed that the masses of CMC and AA,AM and AMPS were 1.00,7.00,1.00 and 0.50 g,respectively,the neutrality degree of AA and AMPS were both 70 %,the amount of initiator was 6.3 % of CMC,and the amount of MBA was 1.4 % of CMC,the Qw and Qs of CS-AAA were respectively larger,which were 618.37 g/g and 93.43 g/g,respectively.FT-IR was used to analyze the composition,and SEM was used to analyze the micro morphology.(4)In the preparing reaction process of CS-AA,CS-AAMPS and CS-AAA,montmorillonite(MMT)was added to prepare MMT-doped super-absorbent polymers,which were named as MMT-doped acrylic acid grafted corn stalk cellulose based super absorbent polymers(CS-AA@M),MMT-doped 2-acrylamido-2-methylpropanesulfonic acid modified acrylic acid grafted corn stalk cellulose-based super absorbent polymers(CS-AAMPS@M)and MMT-doped tri-hydrophilic monomers grafted modified corn stalk cellulose-based super absorbent polymers(CS-AAA@M),and combined with the conditions of CS-AA,CS-AAMPS,CS-AAM and CS-AIA,MMT-doped tetra-hydrophilic monomers grafted modified corn stalk cellulose-based super absorbent polymers(CS-AAAI@M)was prepared.The influences of the amount of MMT on their Qw and Qs were discussed.The experimental results showed that when the dosage of MMT of CS-AA@M,CS-AAMPS@M,CS-AAA@M and CS-AAAI@M were 0.7%,0.9%,0.85%and 2.1%,their Qw and Qs were respectively larger.Qw and Qs of CS-AA@M were 505.12 g/g and 63.44 g/g,CS-AAMPS@M were654.81 g/g and 56.24 g/g,and CS-AAAI@M were 513.36 g/g and 72.85 g/g.SEM was used to analyze the micro morphology.(5)The effects on the germination time,germination rate and seedling growth of Chinese cabbage seeds under the same natural environmental conditions and cultivation methods were discussed by using the water absorption and water retention function of CS-AA,CS-AA@M,CS-AMPS@M and CS-AAAI@M.The experimental results showed that CS-AA,CS-AA@M,CS-AAMPS@M and CS-AAAI@M can not only increase the germination rate of Chinese cabbage seeds,but also shorten the germination time of Chinese cabbage seeds.Compared with the pure nutrient soil without super-absorbent polymers,the nutrient soil supplemented by CS-AA,CS-AA@M,CS-AAMPS@M and CS-AAAI@M can shorten the germination time of Chinese cabbage by 4,6,6 and 5 days,increase the germination rate by 20 %,20 %,30 % and 20 % respectively and increase the average height of the seedlings by 24.2 %,34.1 %,70.2 % and 26.3 %. |
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