Preparation And Sustained-release Performances Of Porous Geopolymers And Their Composites

Geopolymer,a new kind of green inorganic polymer material,has many advantages such as wide source of raw materials,low cost,low environmental pollution,light weight and high porosities.Therefore,geopolymer has broad application and development prospects.At present,the raw materials of geopolymer are mainly concentrated in metakaolin and fly ash.At the same time,the reported geopolymer has single function and limited application.In another side,loess particle,a kind of natural inorganic material with a wide range of sources,cheap,easy to obtain,eco-friendly,rich in hydroxyl groups,small particle size,high specific surface area,and diverse in size and morphology.Semicoke is a kind of cheap industrial product,but the oversupply of the market caused a waste of resources,and easily caused dust and serious pollution to the environment.However,at present,there had a few reports about loess and semicoke-based functional materials.This thesis chose the environment friendly loess particles and industrial cheap products(semicoke)as raw materials,prepared porous geopolymers,which were used to loading agricultural fertilizer and pesticide at the first time.The geopolymer-based slow release fertilizer and pesticide were obtained,and the varieties of performances in the field of agriculture were studied.The thesis mainly includes the following parts:Chapter 1,the development history of geopolymer and the main types of its raw materials was introduced,and the preparation methods and foaming principle of geopolymer were summarized,then the applications of the geopolymer were induced and summarized,in addition,the development and application of geopolymer composites were introduced.Chapter 2,the cheap and porous loess-based geopolymer(Lo-GP)was prepared by alkali excitation-H₂O₂ foaming method,with loess particles(Lo)as the main raw material.The structure and morphology of Lo-GP were characterized by SEM,FT-IR,XRD,BET and TG.The post-treatment methods of Lo-GP with alkalinity were optimized.The adsorption properties of Lo-GP on metal ions(Pb²⁺,Cu²⁺,Cr₂O₇^2-),inorganic anions(PO₄^3-)and dyes(MB,Me B,MG,FB,MO and CV),as well as the adsorption kinetics and thermodynamics of Pb²⁺,PO₄^3-,MG and MB were investigated.The results showed that Lo-GP,a loose and porous loess-based geopolymer was successfully synthesized.After optimized the methods of post-treatments,it was found that Lo-GP with neutral p H value could be obtained by leaching Lo-GP with 0.3wt%KH₂PO₄ solution.The studies of the adsorption performance of Lo-GP on metal ions,inorganic anions and dyes were investigated,it was found that Lo-GP was universal in the field of adsorption,and the removal rates of MG and FB were the highest,which were 99.52%and 98.21%,respectively.After investigating of the adsorption mechanical of Lo-GP,it was found that the adsorption behaviours were chemical and monolayer adsorption.Chapter 3,the environmental friendlily slow release fertilizer(UF@Lo-GP/Gel)based on porous geopolymer was synthesized.The Lo-GP was used as carrier for loading fertilizer,and biocompatible polymers(starch,polyvinyl alcohol)were used as gel coated materials with boric acid as crosslinking agent.The structures and components of UF@Lo-GP/Gel were characterized by SEM,EDS,FT-IR,XRD and TG.The results showed that the organic/inorganic composite porous materials UF@Lo-GP/Gel was successfully synthesized and the porous structure of Lo-GP were retained.The water absorption of UF@Lo-GP/Gel could obtain 660%.Water retention was tested and the result showed that UF@Lo-GP/Gel contained 2.9%moisture on the 55th day.Soil degradation experiment found that the degradation rate of UF@Lo-GP/Gel was 18.39%within 30 days.The soil acidity and alkalinity experiments showed that UF@Lo-GP/Gel could adjust the p H value of acidic soil solution to the neutral environment which was more suitable for plant growth.The release performance of nitrogen fertilizer showed that UF@Lo-GP/Gel has slow release effect(about 50%in 90 days).The plant growth test found that UF@Lo-GP/Gel had the effect on promoting growth of plants,which was 2 to 3 times of plants total quality and chlorophyll content more than the control groups.Chapter 4,firstly,the magnetic and porous semicoke geopolymer(MSC-GP)was synthesized by alkali-excitation H₂O₂ foaming method with semicoke(SC)as the main raw material,and Fe Cl₃/Fe SO₄ as the magnetizer.Secondly,sodium alginate(SA)and Ca Cl₂ were used for pore encapsulation,and the magnetic porous semicoke-based geopolymer slowed release pesticide(MCPA@MSC-GP/SA)was prepared.The MSC-GP was loaded with pesticide(2-methyl-4-chlorine,MCPA).The structure and morphology of MCPA@MSC-GP/SA was characterized by SEM,EDS,FT-IR and TG.The tests of MCPA@MSC-GP/SA on water absorption,water retention,soil degradation,soil acid-base regulation,MCPA slow-release and plant growth were investigated.The results showed that MCPA@MSC-GP/SA was uniform in size and morphology under SA coating,and MSC-GP pore structures were retained inside.Performance tests showed that the bibulous rate of MCPA@MSC-GP/SA in pure water was 461%while 447%in Na Cl solution.The water retention was 4%in 58d and the degradation rate was 33.04%in 30 d.The cumulative release rate of MCPA was 65.2%in 90 d in soil and the plant growth proved MCPA could inhibit weeds growth.All in all,the cheap,abundant resources and environmental friendly natural mineral particles(loess)and industrial cheap products(semicoke)were chose as raw materials,and the new geopolymer composites with relatively simple process were prepared.And the composites were further prepared with loading agricultural fertilizer and pesticide,which could be new materials for slow-release fertilizers and pesticides.The slow-release properties of the materials were examined,and the results showed that the porous structures of geopolymer were beneficial to load fertilizers and pesticides.The slow release materials were cheap and environmentally friendly,which were expected to be widely applied in the field of agricultural planting.The achievements could provide a reference for the development of new environmental protection agricultural materials.