Development and validation of a real-time and non-destructive method for direct measurement of solid mixture based on reflection spectra

Abstract

The Belt and Road countries are facing low resource exploitation efficiency and environmental pollution problems in the field of industrialization and production. Real-time and accurate determination of solid composition is urgently required. Herein, a new quantitative model and method were developed based on the mass conservation law, the elementary reaction and interaction between light and substance. Charge-coupled Device receiver was used to directly measure the solids and quickly obtain the spectral reflectance. According to the difference of spectral reflectance, partial least squares mathematical iterative fitting is utilized to optimize the model parameters based on the relationship between concentration and reflectance at 380–740 nm. It is applied to three typical mineral systems: I. Fe2O3 and Fe3O4 system with different metal valence states; II. ZnO and ZnS system with different anions; and III. Fe2O3 and ZnS system with different element compositions. The best characteristic wavelengths are 560 nm, 720 nm and 680 nm. The goodness of fit is 0.97–0.99 with root mean square less than 0.04, standard recoveries 98%–108%, and relative error of blind sample less than 5%. Compared with some conventional solid analysis methods, this method has the advantages of real-time, non-destructive, no pretreatment and no secondary pollution.