Application Of Palygorskite In Preparation Of Briquette And Determination Of Its Fluorine Content

Coal is the main energy source in China.In recent years,fluoride produced by coal combustion has been paying more and more attention to its influence on the ecological environment and personal health,so the technology of removing fluoride from coal has attracted more attention.Due to the characteristics of low pollution,the research and development of biomass briquette has been widely concerned at home and abroad.Palygorskite clay mineral is abundant in China.Because of its large specific surface area and surface colloidal properties,palygorskite can be used as a good adsorbent and binder.Based on the review of the related literature,in this thesis,briquette was prepared by mixing mushroom residual and coal with high fluorine,and using palygorskite as the binder and fluorine fixing agent for.In the analysis of the fluorine fixation behavior of palygorskite,it was found that the fluorine content of the prepared briquette increased instead.The analysis of the fluorine content in the briquette showed that addition of palygorskite is an important factor affecting the fluorine content in the briquette.Therefore,the determination of fluorine content in palygorskite was further carried out and confirmed.The research contents were as follows:1.Using edible fungus residual and high fluoride contained coal as raw materials,palygorskite clay in Linze district of Gansu province was used as binder and fluoride fixing to prepare biomass briquette.The industrial analysis of briquette was carried out,and the effect of different fluoride fixing agents was investigated.The results showed that the fluorine fixation effect of palygorskite is not good and the fluorine content in briquette prepared is increased.It is inferred that there is fluorine in palygorskite.2.Palygorskite clay in Linze region was purified with sodium hexametaphoshpate,and then modified by acid washing,alkali washing,ultrasonic assisted washing and calcination,respectively.The structure of palygorskite before and after modification was characterized by means of X-ray diffraction(XRD)and scanning electron microscopy(SEM).The elemental composition was detected by X-ray fluorescence spectroscopy(XRF).Based on above analysis,the fluorine content of palygorskite was determined by high temperature combustion hydrolysis-fluorine ion selective electrode method.The results showed that the fluorine content in Linze palygorskite clay mineral is 1098.49 μg/g and is 1305.87 μg/g after purification at the decomposition temperature of 1100℃.Stirred water washing and ultrasonic treatment could not remove the fluorine from palygorskite structure.Acidification treatment can gradually decrease the amount of fluorine released in palygorskite with the increase of acid concentration.The amount of fluorine released in palygorskite increases with the increase of alkali concentration.The amount of fluorine released in palygorskite gradually increased to 1506.86 μg/g with the increase of alkali concentration to 0.5 mol/L,and then do not change significantly,while it is 1296.51 μg/g treated with 0.01 mol/L Na OH.Besides,the amount of fluorine released from increases with the increase of calcination temperature.The above studies indicated that fluorine is present in the structure of palygorskite and exists in different binding forms.3.To further confirm the presence of fluorine in palygorskite,X-ray fluorescence spectroscopy(XRF)and high temperature combustion hydrolysis-fluorine ion selective electrode method were employed to detect the elemental composition and fluorine content in samples collected from Baiyin district of Gansu province,Mingguang district of Anhui province,Xuyi district of Jiangsu province and 98 wt% palygorskite purchased.The results showed that the fluorine content is 1096.95 μg/g in the palygorskite raw ore in Mingguang and 1275.98 μg/g after purification.There are 1131.05 μg/g and 1267.48μg/g in the sample in Xuyi district,respectively.There are 1266.22 μg/g and 1294.28μg/g in the sample in Baiyin district,respectively.The fluorine content in commercially high-purity palygorskite(98 wt%)is 1294.66 μg/g.The determination further proves the presence of fluorine in palygorskite which provides a valuable reference for the redetermination of palygorskite composition and structure.