Study On Determination Of The Weight Concertration Of Free Silicon Dioxide For Dust By Using XRD Technique And The Rietveld Refinement Method

The professional contact including the silicon dust and the lung cancer,as well as silicosis and the lung cancer relational question,has conducted many research from clinical aspects and pathology,epidemiology very early.Recently about pneumoconiosis,specially silicosis merge lung cancer risk has the markup tendency,these aroused the professional medical arena interest.It is already determined that free silicon dioxide for dust not only is the main causeation for silicosis,but also is the major targets or quotas for appraising the dust hazard.In our country,the personnels contact the silicon dioxide dust operating are so many,silicosis sickness digit are so big,therefore,strenuously examining free silicon dioxide for dust content is a very important and urgent work.Recently, the Guangxi occupational disease preventing and controling research institute carried on the investigation to the Hechi's refinery,they discoveried that silicosis digit of different workshop and different working procedure worker is so big. Therefore,in order to discover the cause of disease and control the production dust density,examining the free silicon dioxide content of the refinery fastly and accuratly is very necessary.The weight concentration of free silicon dioxide for simulant dust and actual dust have been determined by using XRD technique and the Rietveld refinement method.At the same time,the weight concentration of the other crystal phases and amorphous were also determined.The experiment was performed on a Rigaku D/max 2500V X-Ray diffractometer,CuKαradiation and graphite monochromator operated at 44kV,150mA.The diffraction data of samples were collected with step scanning method.Qualitative phase analysis of each sample was performed using the Jade 5.0 software program and Rietveld quantitative phase analysis was performed using DBWS9807a.The results were:By analyzing a series of four phases,five phases,six phases simulation dust sample's which the SiO₂ content different,we investigated the affection of peak profile function and structure function to the experimental result:changing peak profile function can make analyses results have great change,but structure function change bring very little affecion to the analyses results.The Rietveld refinement method overcome the legitimate conventional X-ray diffraction about the micro-absorption,orientation,the diffraction peaks overlap and pure samples of difficult issues,because it on the basis of its structural model,including the application of overlapping peaks,all diffraction peak,making the traditional methods of quantitative analysis coursing about the diffraction peaks overlap stripping difficulties and pure samples of the difficult issues have been settled,so that quantitative analysis of the results more accurate and reliable,and the impact of the preferred orientation was a considerable degree of inhibition.The last results are:R_p=8.53%,R_wp=12.02%and S=2.06 on average.The weight concentration absolute error for free silicon dioxide of each sample were 1.54%,2.22%,1.96%and the recovery were 114%,108.53%,92.38% respectively.Other crystal phase concentration absolute error all less than 3% and the recovery was 92.38%～114.65.(2)We analyzed a series of simulation dust sample which contained the amorphous SiO₂:the Rietveld refinement method can be legally accurate determination amorphous phase and the unknown phase of a sample,the method need not be measured in samples of any member of reference standard phase, nor be drown the standard curve as other X-ray diffraction quantitative analysis.The last results are:R_p=8.79%,R_wp=12.11%and S=2.47 on average.The weight concentration absolute error for free silicon dioxide of each sample were 1.19%,0.88%,0.42%and the recovery were 94.32%,96.68%,98.08% respectively,replicated analyzed for SiO₂ showed a relative standard deviation was 1.14%.The weight concentration absolute error for amorphous silicon dioxide of each sample were 1.33%,0.62%,1.81%and the recovery were 112.97%,84.62%,119.91%respectively,the relative standard deviation was 12.45%.Other crystal phase concentration absolute error all less than 3%and the recovery was 91.31%～112.97,the relative standard deviation were less than 5%.(3)After analyzed the actual dust which were offered by Guangxi occupational disease preventing and controling research institute:the Rietveld refinement method to be legitimate for a successful solution,such as SnO₂ and SiO₂ phase-the problem is diffraction peak serious overlapping,it not only simplifies the analysis but also reduction of the emergence of the random error. The Rietveld refinement method also can be fitted the other phase of the content in the mixture at the same time,which is chemical analysis not available.The last results are:R_p=11.09%,R_wp=13.13%and S=3.19 on average.The weight concentration of SiO₂ was in the range of 0%～37.83%and the recovery of in spiked grains ranged from 102.6%～119.9%.The results demonstrate that X-ray powder diffraction technique and the Rietveld refinement method for measuring the percentage composition of free silicon dioxide in dust and other phases are accurate and have a better precision. It is an excellent quantitative method.