Ultrapure water with minimum contents of impurities is used for the
preparation of steam in thermal power plants. More recently it has been found
that the corrosion process is also influenced by sodium ions, chloride ions,
and all forms of silicon in water. At higher temperatures and under high
pressure the less soluble compounds of silicon are extracted, which form
deposits on the walls of the boiler, the piping system and the turbine
blades. Silicon is found in water in the form of different types (species)
which are characterized by specific physical and chemical properties.
Distinctions can be made between highly reactive species of ionic (silicate
anions) and molecular forms (silicic acid) and relatively inert types
(suspended, colloidal, and polymerized silicon). The determination of various
forms of silicon in water is a complex analytical task. This paper covers
relevant research in the field of silicon specification analysis. Maintaining
the unchanged, original composition of silicon species during various stages
of analysis (sample collection, storage, and conservation) has been given
special attention. A large number of methods and procedures have been
developed for the analysis of species of silicon, including chromatographic,
spectroscopic and electrochemical techniques and combinations thereof. The
techniques used for determining both the total amount and individual forms of
silicon have been singled out. There is also an overview of the coupled
techniques used most frequently in practice by using the methodology which
involves preliminary separation of species and then individual specification.
The paper offers an overview of analytical properties, advantages and
disadvantages of the most representative analytical methods developed
specifically for the analysis of silicon species in ultrapure water. The most
important studies focusing on the silicon species in water have been
highlighted and presented in detail. The determination of silicon content in
water is of great importance because of various effects of silicon species
(corrodibility and toxicity) and the selection of methods for the efficient
removal of silicon from water.
Analytical techniques for determination and control of silica content in the water in thermal power plants
