Effectiveness of Filtering Liquid Bleach
The following is excerpted from "A Comparison of Methods for Determining the Concentration
of Transition Metal Ions in Liquid Bleach", a thesis by Hung A. Pham, Miami University,
Oxford, OH 1997. This excerpt provides information that demonstrates the impact
filtering can have on commercially available bleach. The bleach samples provided
for this research were produced on equipment manufactured by Powell Fabrication
and Manufacturing, Inc.
The presence of transition metal (Cu, Fe, and Ni) ions in liquid bleach is a source
of bleach decomposition that results in the build-up of oxygen. The oxygen build-up
causes two problems for a water utility: it signifies that bleach is decomposing
and more product must be used to disinfect the raw water; and the handling of the
highly caustic solution becomes more dangerous due to a pressure build-up in storage containers
and bleach transport piping.
Measurement of transition metal ions at low concentrations is a difficult task because
liquid bleach contains a complicated matrix where the presence of transition metals
can potentially be present as species with various ligands (e.g. Ni(OCl)+,
Ni(OH+, NiCl+, etc.).
Methods to identify and routinely measure the transition metal ion species at concentrations
below 1 mg/l in liquid bleach have not been developed. The purpose of this research
was to explore, optimize, and validate analytical methods that can be routinely used
to measure transition metal ion concentrations in bleach.
Five methods (Visual Spot Test, Inductively Coupled Plasma, Chemometric Analysis,
Chloroform Extraction Colorimetric and Ion Chromatography Postcolumn) have been
evaluated in this study. The Ion Chromatography Postcolumn is the best method for
determination of three transition metal ions because it has high precision, good
accuracy, and a low limit of detection (less than 10 μg/L).
From Chapter IV, A Comparison of Methods for Determining the Concentration of Transition
Metal Ions in Liquid Bleach, a thesis by Hung A. Pham, Miami University, Oxford,
The presence of transition metal ions is known to catalyze the decomposition of
bleach to form O2. Build up of O2 in storage tanks and pipes has become a safety
issue for suppliers and water utilities. The presence of transition metal ions contributes
to the loss of bleach strength. New specifications by water utilities to check transition
metal ion concentrations in delivered bleach have been initiated. Therefore, suppliers
and water utilities require simple and convenient transition metal ion analysis
We felt it is necessary to test a number of commercially available bleach
samples. This will define a typical transition metal (Cu, Fe and Ni) ion
concentration range in bleach. Mr. Duane Powell PE, Powell Fabrication and
Manufacturing, Inc., St. Louis, Michigan, provided a number of bleach samples for analysis.
Data from these representative commercially available bleach samples are presented
in Table 4 comparing Chloroform Extraction Colorimetric (CEC) and Ion Chromatography
This article is available as a PDF. Click here to download it. For
more information about sodium hypochlorite (liquid bleach), visit the Technical Information