Refinement And Purification Of Gansu Linze Attapulgite And Its Application In Polymer Materials

The unique chain structure of attapulgite makes it possess many excellent physical and chemical properties,such as good chemical stability,large specific surface area,strong adsorption capacity,good suspension and slow release ability.Because of its excellent physical and chemical properties,attapulgite has been widely used in food,construction,textile,medicine,catalyst and environmental protection and many other fields.According to preliminary estimates,the reserves of the attapulgite deposit in Linze,Gansu Province are about 735 million tons,accounting for about 50% of the world’s attapulgite reserves.Yangtaihuatan Basin,located in the northern part of Linze County,Gansu Province,is rich in attapulgite and gypsum composite ore.The attapulgite deposit in Linze,Gansu province greatly changes the distribution pattern of attapulgite mineral resources in the world,which provides strong support for the sustainable development of attapulgite industry in our country.In order to make the attapulgite ore in Linze area more efficient in the application of output value,based on the analysis of various physical and chemical properties of the attapulgite ore,this paper uses simple physical and chemical purification methods to refine and purify the attapulgite concentrate as a flame retardant applied in the vinyl vinyl acetate copolymer(EVA)wire and cable sheathing.This paper is mainly carried out from the following three aspects:1.Through the whole rock mineral composition analysis,Linze attapulgite ore components are mainly attapulgite,quartz,plagioclase and illite.Among them,the highest content of attapulgite is only 36%,quartz is 26.1%,plagioclase is 13.9%,and illite is 8.8%.The content of these four mineral components is about 84.8%.Under scanning electron microscope,attapulgite coexists with quartz and other associated minerals in raw ore,and clusters into large spherical particles,coating each other without effective dispersion and peeling.There are short rod-like aggregates on the surface of the spherical particles with dense structure and disordered arrangement.The aggregates are rod-crystal aggregates of attapulgite.Through XRD and infrared characterization of Linze attapulgite primary ore,we can find that the main composition of Linze attapulgite primary ore is attapulgite clay,and the impurities are mainly quartz and carbonate minerals.2.Through simple physical and chemical methods,the attapulgite ore in Linze area is refined and purified,and the best purification process of attapulgite ore in Linze area is selected by using the characterization means of whole rock mineral analysis,XRD,SEM and infrared spectrum analysis.Firstly,the one-step and one-step centrifuge beneficiation tests of Gansu Linze attapulgite raw ore with ultrasonic dispersion were carried out by physical purification method and high-speed centrifuge.The effects of centrifugal speeds at 2000r/min,4000r/min,6000r/min,8000r/min and 10000r/min on the yield and purity of attapulgite were discussed in detail.Combined with the upper and lower yield and the whole rock analysis,the results showed that the best purification effect was achieved at 8000 r/min,the yield of attapulgite was 32.38% and the purity was 56.8%.Through the fractional centrifugal method,the time is fixed for 3 min,and the rotational speed is set as 1600r/min,1800 r/min,2000 r/min,2200 r/min,2400 r/min.Combined with the upper and lower yield and the whole rock analysis test of minerals,the following results are obtained: At 2200 r/min,the yield of attapulgite was 35.84% and the purity was59.2%.After a fixed centrifugation time of 3min and a centrifugation rotation of8000r/min,Linze attapulgite is purified by using five kinds of inorganic and organic dispersants such as sodium hexametaphosphate,sodium silicate,polyethylene glycol,polyacrylic acid and oxalic acid as well as pulp pH.After whole rock mineral analysis,XRD,SEM and infrared spectrum analysis and other characterization methods,It is found that the purity of attapulgite with 3% sodium hexametaphosphate is the highest when the pulp pH is 12,and the content of quartz impurity is only 1.6%.3.The attapulgite concentrate purified by the best purification process is used as a flame retardant in ethylene-vinyl acetate copolymer(EVA)wire and cable sheathing.In terms of mechanical properties,the elongation at break of 1% purified attapulgite /EVA composite increased by 5.3% compared with the standard sample,and was higher than that of 1% attapulgite raw ore.In terms of oxygen index and smoke density properties,after adding 1% purified attapulgite,the ultimate oxygen index of composites increased from 38 to 38.3,the smoke volume of composites was reduced by 4.36%,and the maximum smoke generation time was delayed by 50.5s,indicating that the addition of purified attapulgite could improve the smoke suppression performance of composites.According to conical calorimetric analysis of materials,after adding attapulgite to EVA composites,the flame retardant properties of the composites are improved to varying degrees,and after adding 1% purified attapulgite to EVA composites,peak heat release rate(PHRR)and total heat release rate(THR)are reduced by 7.1% and 12.38%,respectively.Fire spread index(FGI)decreased by 16.88%,heat release within specified time(THRI6min)and smoke release within specified time(TSPI6min)decreased by 2.68% and 11.06%,and the performance of raw ore with 1% attapulgite was better than that of raw ore with 1%attapulgite.