Preparation Of Diatomite Geopolymer Composites And Their Performance

As a natural clay material,diatomite is widely used as industrial filler,such as wettable powder,dryland herbicide,paddy field herbicide and various biological pesticides because of its neutral p H,non-toxic,strong adsorption performance,excellent extensibility,high impact strength,tensile strength,wear resistance and heat resistance.However,there are few researches in the field of functional materials,so the development of diatomaceous earth-based functional materials is worth expanding and researching.Geopolymer is a kind of synthetic silico-aluminate inorganic polymer materials.Due to its characteristics of relatively simple preparation process,strong stability,diverse functions and ecological friendliness,it has gradually attracted the attention of scientists in the field of engineering and materials.In this paper,diatomite,a clay mineral with abundant resources and porous structure,was used as silicate raw material to prepare diatomite geopolymer with porous structure and ecological friendly diatomite geopolymer composite material,and its various properties in the agricultural field were studied.The paper consists of the following main sections:Firstly,the preparation and application fields of diatomite composites are summarized based on the introduction of the main components,structural characteristics,physicochemical properties,main modification methods and applications of diatomaceous earth.Then,the application of diatomite in the field of agriculture was highlighted.Secondly,diatomite porous geopolymer（Dp G）was prepared from diatomite（De）by alkali excitation method.The structures and properties of Dp G was characterized by FT-IR,SEM,EDS,XRD and XPS.It was applied to the adsorption of metal ions(Pb²⁺,Cu²⁺and Cr⁶⁺)and inorganic anions(PO₄^3-).The effects of the amount of Dp G,the concentration of metal ions(Pb²⁺),the p H value of solution,time and temperature on the adsorption properties were investigated.t was found to remove up to 97.34%of Pb²⁺under optimal conditions,and the Pb²⁺removal rate of DPG remained at 63.13%after 6 cycles.By studying the thermodynamic and kinetic models of Pb²⁺adsorption by Dp G.Diatomite geopolymers have been found to adsorb primarily by chemisorption and monolayer adsorption.In conclusion,the prepared diatomite porous geopolymer（Dp G）have loose porous structure and universality in removing metal ions,which is an eco-friendly material and has good application potential in the field of water treatment of heavy metals.Thirdly,Using the prepared Dp G as the carrier,polydimethylurea-potassium phosphate(P（NPK）as the nutrient source,and acrylic acid（AA）and acrylamide（AM）as the polymerization monomers,a new type of geopolymer based multifunctional fertilizer（P（NPK）@Dp G/PAMA）was prepared and the process conditions were optimized.The structure morphology and properties were characterized by FT-IR,SEM,EDS,XRD and XPS.Its slow release properties of soil nutrients,swelling performance and water retention properties under different conditions were investigated and used in corn growth.The results showed that the maximum swelling rates of P（NPK）@Dp G/PAMA in distilled water and normal saline solutions were 194.17 g/g and 71.43 g/g.After 8 times of cyclic swelling,the swelling rate was 156.94 g/g,which was 58.03%of the initial water absorption.The soil contained 3%P（NPK）@Dp G/PAMA retained 26.67%of water after being left open for 70 days in a dry indoor environment.The leaching experiment showed that the cumulative P release of P（NPK）@Dp G/PAMA was 34.6%at 60 d.In addition,P（NPK）@Dp G/PAMA could significantly improve the growth and development indexes of maize,promote plant growth and root nutrition supplement,and is expected to be applied in agricultural planting.At last,FK composite material with nitrogen fertilizer（Urea@Dp G/FK-PAA）was prepared by loading urea with Dp G as a porous carrier.And then extracting keratin（FK）from waste chicken feathers and further in situ polymerization with acrylic acid（AA）as a monomer.It was characterized by FT-IR,SEM,EDS and XRD.The effect of the proportion of raw materials on the water absorption properties of the composites was studied.The water absorption and retention properties of the materials were studied under different conditions.It was also used for seed growth test of tetrapleurophylla.The theoretical maximum swelling rate of Urea@Dp G/FK-PAA in distilled water and 0.9%Na Cl solution is 714.29 g/g and 100.03 g/g,showing excellent salt tolerance.After 8 times of cyclic swelling,the swelling rate of Urea@Dp G/FK-PAA was still 209.8 g/g and still contained 31.65%%water in soil after 120 d.In addition,Urea@Dp G/FK-PAA released 35.97%of nutrients at 45 d,which effectively promoted seed germination.In conclusion,in this paper,porous geopolymers with excellent properties have been successfully prepared by using abundant diatomite and relatively simple method.The practical and multifunctional geopolymer matrix composites were prepared by further loading fertilizer.The material not only has good slow-release properties,but also could effectively promote plant growth.It is expected to be used as a slow release fertilizer in agriculture and provide a new idea for the development of agriculture and chemistry.