Study And Application On Analysis Of Slurry Using Laser-induced Breakdown Spectroscopy

The mineral flotation process is the most important and versatile processing technique in the mineral processing industry,which is used to separates target minerals from raw ores.In the process of flotation,the grade of slurry is an important parameter which determines the output of the concentrate.Therefore,it is of great value for online monitoring and application of slurry.Laser-induced breakdown spectroscopy(LIBS)is a developing analytical technique,which can satisfy the demands of online monitoring for its feature,such as in situ,rapid,and real-time analysis.However,the liquid interference and sedimentation are the major problems when applying LIBS to analyze slurry directly,which cause poor spectral intensity and unstable results.How to solve the above these problems is the key to apply LIBS to slurry analysis.To address these problems and improve spectral intensity and stability,a slurry samples circulation system was devised in this study and a LIBS detection system was established on this basis.The concrete research contents are as follows:(1)A slurry samples circulation system was devised,which could avoid slurry sedimentation effectively and restrict liquid interference.The LIBS detection system was established by combining LIBS system and this circulation system.The optimum experimental parameters for LIBS measurements were investigated to get the best results.The results showed that the detection limits of Fe was estimated to be 0.075 wt.%and the calibration curve for Fe shows a good linear fit(R~2=0.982).To verify the prediction accuracy of the calibration curve,leave-one-out cross-validation was used to test the performance of the method.The results showed that the root-mean-square error prediction was 0.218 wt.%and average relative error prediction was 6.96%,which demonstrated that the prediction accuracy of the calibration curve is acceptable.(2)To further improve the intensity and stability of LIBS signals,a high-frequency pulsed fiber laser was introduced to assist the original system.The signal enhancement mechanism was investigated in terms of the generation and the evolution of plasma.The results showed that the fiber laser could quickly remove the moisture in slurry samples at the detection point and provide a stable and hotter environment for the production of plasma.Moreover,the higher-temperature and lower-density plasmas were created in the improved system.(3)By comparing the spectra of elements collected from the original system and the improved system,the improvement effect of fiber laser on spectral signal is discussed.The results showed that the best enhancement factors for the emission lines of Fe and Ca were about 3.71 and 8.05,respectively.The relative standard deviation of two elements were improved about 11.72%and 9.83%,respectively.The limit of detection(LOD)for Fe in the original system was 0.113wt.%,meanwhile,the LOD of improved system was0.083wt.%at the same experimental parameters.In a word,the designed detection system can reduce the influence of liquid interference and sedimentation effectively and online analyze the iron ore slurry.Therefore,this study provides a new way for the application of LIBS in slurry analysis.