Laser & Optoelectronics Progress, Volume. 59, Issue 1, 0130001(2022)
Design of Water Quality COD Online Detection System Based on Ultraviolet-Visible Spectroscopy
Figures & Tables(10)
Fig. 2. Absorption spectrum of COD standard solution. (a) Transmitted light intensity curve; (b) absorbance curve
Fig. 3. Spectral data prediction regression model. (a) 220~245 nm band; (b) 260~285 nm band
Fig. 4. COD concentration-voltage data model. (a) Normalized spectral curve; (b) voltage regression model; (c) voltage solution model
Fig. 5. Absorption spectrum of mixed solution. (a) Absorbance curve of mixed solution with COD concentration of 50 mg/L and different turbidity; (b) absorbance curve of standard turbidity solution; (c) absorbance of the mixed solution minus the absorbance of the turbidity solution
Fig. 6. Compensation model. (a) Rrelationship between KN and wavelength under different turbidity; (b) compensated absorbance curve
Fig. 7. Absorption spectra of 50 mg/L COD solution at different temperature. (a) Transmitted light intensity curve; (b) absorbance curve; (c) fitting equation at 250 nm wavelength
Table 1. Relative error of the predicted value of COD concentration under different algorithm models
View tableTable 1. Relative error of the predicted value of COD concentration under different algorithm models
COD/
（mg·L-1）
220~245 nm wavelength PLS algorithm model 260~285 nm wavelength PLS algorithm model Voltage solution model Predictive value /（mg·L-1） Relative error /（mg·L-1） Predictive value /（mg·L-1） Relative error /（mg·L-1） Predictive value /（mg·L-1） Relative error /
%
5 4.9118 -0.0178 5.2664 0.0533 5.1557 0.0311 10 10.6633 0.0663 9.8818 -0.0118 10.8115 0.0811 15 15.6599 0.0440 15.6939 0.0463 13.7623 -0.0825 20 19.9684 -0.0016 19.5969 -0.0202 20.8115 0.0406 25 24.9227 -0.0031 24.5523 -0.0179 24.9918 -0.0003 30 29.8816 -0.0039 29.3947 -0.0202 30.0738 0.0025 35 34.5830 -0.0119 42.4895 0.2140 35.0738 0.0021 40 40.7377 0.0184 40.4746 0.0119 38.2705 -0.0432 45 45.0068 0.0002 45.1604 0.0036 44.2541 -0.0166 50 50.1648 0.0033 42.4895 -0.1502 51.8771 0.0375
Table 2. Fitting formula of KN(λ) under different turbidities
View tableTable 2. Fitting formula of KN(λ) under different turbidities
Turbidity（NTU） R2 10 y = -0.0003966x2 + 0.16503x-15.77201 0.99363 20 y = -0.00045692x2 + 0.19838x-20.44448 0.99385 30 y = -0.00050976x2 + 0.23691x-26.59873 0.99542 40 y = -0.00056239x2 + 0.26968x-31.41166 0.99611 50 y = -0.00065806x2 + 0.32548x-39.25635 0.99817
Table 3. Statistical results of linear regression equation at different wavelengths
View tableTable 3. Statistical results of linear regression equation at different wavelengths
Characteristic wavelength /nm Evaluation index Characteristic wavelength（nm） Evaluation index r R2 MSE r R2 MSE 250 0.98650 0.97315 0.00008 275 0.98295 0.96619 0.00012 255 0.98640 0.97299 0.00009 280 0.98195 0.96422 0.00012 260 0.98580 0.97172 0.00009 285 0.98036 0.96111 0.00013 265 0.98500 0.97026 0.00010 290 0.97771 0.95591 0.00014 270 0.98430 0.96874 0.00010 295 0.97461 0.94986 0.00016
Tools
Get Citation
Copy Citation Text
Jiacheng Cai, Xiao Deng, Chongxuan Kan, Shuang Zhao. Design of Water Quality COD Online Detection System Based on Ultraviolet-Visible Spectroscopy[J]. Laser & Optoelectronics Progress, 2022, 59(1): 0130001
Paper Information
Category: Spectroscopy
Received: Mar. 22, 2021
Accepted: Apr. 30, 2021
Published Online: Dec. 23, 2021
The Author Email: Xiao Deng (dengxiao@tyut.edu.cn)
© Copyright 2018-2021 | Chinese Laser Press.
All Rights Reserved 沪ICP备15018463号-20