Matrix Effect Correction Method For Detection Of Heavy Metals In Waste Incineration Fly Ash By Laser-induced Breakdown Spectroscopy

With the continuous development of urbanization,reasonable treatment of municipal solid waste has become an increasingly important issue.At present,usually the main solution method is harmless treatment after incineration.Heavy metal elements are the main harmful substances in municipal solid waste incineration(MSWI)fly ash.At present,the commonly used technologies can not meet the needs of real-time detection of heavy metals in MSWI fly ash.Because the pretreatment process of these technologies for detecting heavy metals in MSWI fly ash is usually complicated.At the same time,the measurement cycle is time-consuming and prone,which leads to secondary pollution.Laser Induction Breakdown Spectroscopy(LIBS)has the advantages of fast,in-situ,simple sample processing,etc.It has great potential to detect heavy metal elements in MSWI fly ash.The physical and chemical characteristics of municipal solid waste changes dramatically due to its wide sources.Therefore,there is a significant matrix effect in the detection of heavy metals in MSWI fly ash by LIBS,which brings more challenges to the accurate measurement by LIBS than other solid samples(such as metals,coal-fired fly ash,etc.).In this paper,the problem of matrix effect in the detection of heavy metals in MSWI fly ash was studied.The influence of matrix effect on the plasma spectrum of MSWI fly ash was analyzed,and different correction methods of matrix effect were studied.Firstly,a physical modification method of mixing additive with MSWI fly ash was proposed.KCl was selected as additive through comparative experiments,and then the mixing ratio was optimized,the best mixing ratio was 30%.Finally,the correction effect was verified by quantitative analysis experiments.Taking Pb as an example,The Fitting coefficient(R~2)of multivariable calibration model was increased from 0.801(original sample)to 0.951(30%mixing ratio).In addition,a matrix effect correction method of coupling wire mesh on MSWI fly ash surface was proposed.Ni was selected as wire mesh material through comparative experiments,and its optimum aperture was studied.The correction effect was verified by quantitative analysis experiments.The results show that the Ni mesh with a diameter of 50μm has the best correction effect.Taking Pb as an example,the R~2 of multivariate calibration model increased from 0.950(original sample)to 0.982(50μm Ni metal mesh).Finally,the optimization performance of the above two correction methods synthetically was evaluated by quantitative analysis experiment.Taking Pb as an example,the R~2 of multivariable calibration model was improved from 0.950(original sample)to 0.990(comprehensive optimization).