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Iron in boiler feed water

AN-V-179

2021-09

zh

Straightforward, sensitive, and cost-efficient determination using adsorptive stripping voltammetry (DHN method)

须对锅炉给水中的铁浓度进行监控，以确保水-蒸汽回路的可靠和安全运行。采用吸附剥离伏安法（AdSV），以 2,3- 二羟基萘（DHN）为络合剂，可高灵敏度地测定锅炉给水中的总铁浓度。伏安法是原子吸收光谱法（AAS）或电感耦合等离子体法（ICP）之外的一种可行的、不太复杂的铁测定方法，只需适度的硬件投资和较低的运行成本。

The iron concentration in boiler feed water must be monitored to ensure reliable and safe operation of the water-steam circuit in thermal power plants. Iron ions, even in low concentrations, are an indicator for corrosion and therefore can signal potential safety issues. Various guidelines set limits for the maximum iron content in boiler feed water. 

The concentration of total iron in boiler feed water can be determined with high sensitivity using adsorptive stripping voltammetry (AdSV) using 2,3-dihydroxynaphthalene (DHN) as complexing agent. Concentrations of total iron in water samples can be determined down to approximately 0.1 μg/L with this method. 

The AdSV method is simple to perform, specific, and free of interferences. It is a viable, less sophisticated alternative to atomic absorption spectroscopy (AAS) or inductively coupled plasma (ICP) requiring only a moderate investment in hardware and low running costs.

Boiler feed water  

Figure 1. 884 Professional VA.

The water sample, DHN solution, and the buffer solution are pipetted into the measuring vessel. The determination of total iron is carried out with an 884 Professional VA using the parameters specified in Table 1. The concentration is determined by two additions of an iron standard addition solution. 

Table 1. Parameters for adsorptive stripping voltammetric (AdSV) analysis of Fe in boiler feed water
Parameter Setting
Working electrode HMDE
Mode DP – Differential Pulse
Deposition potential  -0.1 V
Deposition time  30 s
Start potential  -0.2 V 
End potential  -1.2 V 
Peak potential Fe  -0.7 V 
  • Working electrode: Multi-Mode Electrode pro with standard glass capillaries
  • Reference electrode: Ag/AgCl/KCl (3 mol/L) reference electrode with electrolyte vessel. Bridge electrolyte: KCl (3 mol/L) 
  • Auxiliary electrode: Platinum rod electrode

The determination of total iron in boiler feed water samples can be carried out in a simple  and straightforward manner with adsorptive  stripping voltammetry (AdSV).

Figure 2. Determination of total Fe in boiler feed water.
Table 2. Results of total Fe determination with the 884 Professional VA
Sample Total Fe [μg/L]
Boiler feed water 3.0
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Internal reference: AW VA CH4-0513-072012

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