Simultaneous dynamic spectrophotometric determination of coexisting rare earth elements in acidic chloride media using response-specific multivariate calibration.

Authors

Lei Li, Bin Wang, Guobiao Li, Guoping Hu, Huizhong Liu, Jinfa Liao, Hongdeng Qiu, Haifeng Wang

Published in

Analytica chimica acta. Volume 1427. Pages 346403. Dec 15, 2026. Epub Oct 15, 2026.

Abstract

Reliable spectrophotometric determination of coexisting rare-earth elements in strongly acidic chloride media remains analytically challenging because of weak 4f-4f absorption responses, severe spectral overlap, and baseline instability under dynamic measurement conditions. This study presents a dynamic absorption spectroscopic method coupled with a response-specific multi-scale peak-basis linear regression model (RS-MPBLR) for continuous in situ quantification of Nd³⁺ and Pr³⁺ in strongly acidic coexisting systems relevant to NdFeB magnet recycling. Characteristic absorption peaks, multi-scale spectral descriptors, and derivative-related features were integrated to enhance response specificity and robustness against spectral overlap, acidity-dependent background variation, and flow-induced baseline drift. Spectral analysis confirmed an approximately linear absorbance-concentration relationship within the investigated range, supporting peak-oriented linear modeling. RS-MPBLR was evaluated using leave-one-concentration-out cross-validation and benchmarked against partial least squares, principal component regression, and ridge regression, achieving lower prediction errors and more stable error distributions. Dynamic online experiments demonstrated continuous tracking of stepwise concentration changes, with R² values above 0.97 and limits of detection of 0.07 and 0.03 g/L for Nd³⁺ and Pr³⁺, respectively. Cross-day segment-wise analysis further confirmed stable online predictions, with coefficients of variation mostly below 1-2% and σ_pred values within 0.015-0.040 g/L for Nd³⁺ and 0.006-0.021 g/L for Pr³⁺. This study provides a robust and sensitive spectrophotometric soft-sensing strategy for continuous rare-earth ion quantification in hydrochloric acid media. By combining response-specific modeling with reference-sample-based calibration correction, it overcomes the difficulty of long-term dynamic detection under online flowing conditions and enables reliable quantification for NdFeB magnet hydrometallurgical recycling.

PMID:
43003562
Bibliographic data and abstract were imported from PubMed on 10 Nov 2026.

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