基于数字成像比色法对水中不同价态锰浓度的测定

Determination of Manganese Concentrations with Different Valences in Water Based on Digital Imaging Colorimetry

电解锰的工业废水中含有高浓度的锰。文章建立了基于数字成像比色法快速测定计算水中不同价态锰浓度的方法。在酸性条件下,三价锰[Mn(Ⅲ)]和四价锰[Mn(Ⅳ)]与2,2-联氮-二(3-乙基-苯并噻唑-6-磺酸)二铵盐(ABTS)反应(1∶1和1∶2),产生绿色的ABTS自由基(ABTS·+)。在酸性和过量焦磷酸钠络合剂(PP)条件下,通入过量的臭氧会使二价锰[Mn(Ⅱ)]变为七价锰[Mn(Ⅶ)],Mn(Ⅶ)与ABTS反应的计量关系为1∶5。通过手机对显色溶液进行拍照,将图片导入用Python语言编译好代码的软件中来获取红、绿、蓝三色通道(RGB)值,同时利用其高效的计算能力,对不同价态的锰进行测定计算。在优化的试验条件下,吸光度与RGB的信号中对应的红色通道(R值)成线性关系,线性方程为y=-0.018x+2.46,相关系数(R2)为0.991,检出限为0.03。该方法具有检测效率高、成本低、准确性高的特点,同时可用于电解锰的废水排放时锰的在线监测。

The industrial wastewater of electrolytic manganese containes high concentration of manganese.The method for rapid determination and calculation of different valence of manganese concentrations in water based on digital imaging colorimetry was established.In acidic conditions,trivalent manganese[Mn(Ⅲ)]and tetravalent manganese[Mn(Ⅳ)]reacted with ABTS to produce green ABTS radicals(ABTS·+),and the stoichiometric relationships were 1∶1 and 1∶2,respectively.In acidic and excessive sodium pyrophosphate complexing agent(PP)conditions,the introduction of excessive ozone would make divalent manganese[Mn(Ⅱ)]into seven valence manganese[Mn(Ⅶ)].The stoichiometric relationship between Mn(Ⅶ)and ABTS was 1∶5.The color solution was photographed by mobile phone,and the picture was imported into the software compiled by Python language to obtain the RGB value.At the same time,its efficient computing ability was used to measure and calculate manganese with different valence states.In the optimized experimental conditions,the absorbance was linearly related to the corresponding red channel(R value)in the RGB signal.The linear equation was y=-0.018x+2.46 with R2=0.991,and the detection limit was 0.03.This method has the characteristics of high detection efficiency,low cost and high accuracy,and it can be used for on-line monitoring of manganese during the discharge of electrolytic manganese wastewater.