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    					| UV-Visible Spectral Characteristics and Quantitative Analysis of the 
MnSO4-H2SO4 System | 
  					 
  					  										
						| XU Yan-li, XU Fu-yuan, DUAN Ning* | 
					 
															
						College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
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													     		                            						                            																	    Abstract  The complex pretreatment requirements and delayed analytical response inherent in conventional methods constitute major challenges for monitoring high-acid, high-manganese systems (H2SO4≤2 mol·L-1, Mn2+≤1.2 mol·L-1) within the hydrometallurgical industry. For effective process management and optimization, rapid and accurate monitoring of Mn2+ concentration within high-concentration H2SO4 matrices is crucial. This study aimed to develop a rapid and direct determination method based on ultraviolet-visible (UV-Vis) spectroscopy to overcome spectral interference arising from the significant overlap between the absorbances of Mn2+ and H2SO4. The goal was to enable direct quantification of Mn2+ within MnSO4-H2SO4 systems, thereby providing an innovative solution for high-frequency industrial monitoring. The study systematically characterized the spectral properties of H2SO4 solutions across a concentration range of 0~18 mol·L-1. Utilizing spectral similarity analysis techniques—including Spectral Correlation Measure (SCM), Euclidean Distance Measure (EDM), and Spectral Information Divergence(SID)—wavelengths exhibiting minimal H2SO4 interference were identified. Furthermore, the detection sensitivity for Mn2+ was enhanced using a long optical path strategy (100 mm). A robust quantitative model was established for Mn2+ within the industrially relevant concentration range (≤60 g·L-1). Key findings demonstrate that the absorption peak of H2SO4 within the 180~230 nm region (λmax≈185~195 nm) shows substantial overlap with the MnSO4 absorption. The core sources of interference identified were the concentration-dependent wavelength shift of this H2SO4 peak and the enhanced SO2-4 absorption due to Mn2+ coordination. Crucially, H2SO4 exhibits negligible absorption at 400 nm, a wavelength where the Mn2+ complex showed stability. Model validation yielded excellent performance: predicted absolute relative errors |RE| and relative standard deviations (RSD) both remained below 5%, with a coefficient of determination (R2) exceeding 0.99. This research pioneered a collaborative spectral interference decoupling-long optical path enhancement strategy. A UV-Vis spectroscopic detection method was developed that achieves rapid and accurate quantification of Mn2+ in high-concentration H2SO4 solutions, eliminating the need for dilution or pretreatment. This approach offers advantages in speed, cost-effectiveness, and precision, making it well-suited for monitoring requirements in industrial leaching and electrolytic refining processes. The strategy holds significant guiding potential for analyzing other inorganic salt electrolysis systems and provides a crucial foundation for improving hydrometallurgical efficiency while reducing environmental burdens.
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											   							Received: 2025-04-19    
						    						    							Accepted: 2025-09-03    
						    						    						    																				    
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																Corresponding Authors:
																DUAN Ning   
																																 E-mail: ningduan@tongji.edu.cn
															    													     		
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