Abstract
Excessive discharge of heavy metal ions will aggravate environment pollution and threaten human health. Thus, it is of significance to real-time detect metal ions and control discharge in the metallurgical wastewater. We developed an accurate and rapid approach based on the singular perturbation spectrum estimator and extreme gradient boosting (SPSE-XGBoost) algorithms to simultaneously determine multi-metal ion concentrations by UV–vis spectrometry. In the approach, the spectral data is expanded by multi-order derivative preprocessing, and then, the sensitive feature bands in each spectrum are extracted by feature importance (VI score) ranking. Subsequently, the SPSE-XGBoost model are trained to combine multi-derivative features and to predict ion concentrations. The experimental results indicate that the developed “Expand-Extract-Combine” strategy can not only overcome problems of background noise and spectral overlapping but also mine the deeper spectrum information by integrating important features. Moreover, the SPSE-XGBoost strategy utilizes the selected feature subset instead of the full-spectrum for calculation, which effectively improves the computing speed. The comparisons of different data processing methods are conducted. It outcomes that the proposed strategy outperforms other routine methods and can profoundly determine the concentrations of zinc, copper, cobalt, and nickel with the lowest RMSE. Therefore, our developed approach can be implemented as a promising mean for real-time and on-line determination of multi-metal ion concentrations in zinc hydrometallurgy.
Highlights
Zinc metal smelting wastewater contains multiple toxic metal ions, such as zinc, copper, cobalt, and nickel
To highlight the characteristic information of each ion, different singularly perturbation parameter ε is selected in the singular perturbation spectral estimator (SPSE) to get the denoising spectrum and the first-order and second-order derivative spectra
We developed the SPSE-XGBoost approach to simultaneously measure the multi-metal ion concentrations by UV–vis spectroscopy in the complex zinc sulfate solutions
Summary
Zinc metal smelting wastewater contains multiple toxic metal ions, such as zinc, copper, cobalt, and nickel. Irrational discharge of heavy metal ions will cause serious harm to the ecological environment [1,2]. The concentrations of metal ions are mostly acquired via off-line analysis in the laboratory, which is laborious, time-consuming, connects with many errors and chemical costs, and leads to blind control of wastewater discharge. The real-time and accurate detection of metal ions is urgently needed [3]. The UV-vis spectrophotometry can achieve online analysis on multi-ions without expensive
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