Near-infrared spectroscopy for the prediction of rare earth elements in soils from the largest uranium-phosphate deposit
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Near-infrared spectroscopy for the prediction of rare earth elements in soils from the largest uranium-phosphate deposit in Brazil using PLS, iPLS, and iSPA-PLS models Angelo Jamil Maia & Yuri Jacques Agra Bezerra da Silva & Clístenes Williams Araújo do Nascimento & Germano Veras & Maria Eugenia Ortiz Escobar & Cleyton Saialy Medeiros Cunha & Ygor Jacques Agra Bezerra da Silva & Rennan Cabral Nascimento & Lavínia Hannah de Souza Pereira
Received: 8 May 2020 / Accepted: 24 September 2020 # Springer Nature Switzerland AG 2020
Abstract The largest uranium-phosphate deposit in Brazil also contains considerable levels of rare earth elements (REEs), which allows for the co-mining of these three ores. The most common methods for REE determination are time-consuming and demand complex sample preparation and use of hazardous reagents. Thus, the development of a safer and faster method to predict REEs in soil could aid in the assessment of these elements. We investigated the efficiency of near-infrared (NIR) spectroscopy to
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10661-020-08642-2) contains supplementary material, which is available to authorized users. A. J. Maia : C. W. A. do Nascimento : Y. J. A. B. da Silva : R. C. Nascimento Agronomy Department, Federal Rural University of Pernambuco (UFRPE), Dom Manuel de Medeiros street, s/n - Dois Irmãos, Recife, PE 52171-900, Brazil Y. J. A. B. da Silva (*) Agronomy Department, Federal University of Piaui (UFPI), Planalto Horizonte, Bom Jesus, PI 64900-000, Brazil e-mail: [email protected] G. Veras : L. H. de Souza Pereira Chemistry Department, State University of Paraiba, Baraúnas St. 351, Campina Grande, PB 58429-500, Brazil M. E. O. Escobar : C. S. M. Cunha Soil Science Department, Federal University of Ceará (UFC), Av. Mister Hull, s/n, Campus do Pici, Fortaleza CE 60455-760, Brazil
predict REEs in the soil of the uranium-phosphate deposit of Itataia, Brazil. We collected 50 composite topsoil samples in a well-distributed sampling grid along the deposit. The NIR measures in the soils ranged from 750 to 2500 nm. Three partial least squares regressions (PLSR) were selected to calibrate the spectra: full-spectrum partial least squares (PLS), interval partial least squares (iPLS), and successive projections algorithms for interval selection in partial least squares (iSPA-PLS). The concentrations of REEs were measured by inductively coupled plasma optical emission spectroscopy (ICP-OES). In addition to raw spectral data, we also used spectral pretreatments to investigate the effects on prediction results: multiplicative scatter correction (MSC), Savitzky-Golay derivatives (SG), and standard normal variate transformation (SNV). Positive results were obtained in PLS for La and ΣLREE using MSC pretreatment and in iSPA-PLS for Nd and Ce using raw data. The accuracy of the measurements was related to the REE concentration in soil; i.e., elements with higher concentrations tended to present more accurate results. The results
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