Getting Technical
CHARLES NICOLSON
Charles Nicolson has a physics and chemistry degree from Natal University which he subsequently put to
good use by applying speciality chemicals in mining and industrial processes where water is a major factor.
This created an enduring interest in water technology, a passion that expanded to the HVAC industry
in 1984 when he joined BHT Water Treatment. Since then, water technology in HVAC water circuits has
continued to be an abiding interest.
LOOKING AT ELECTROLYSIS
By Charles Nicolson
Electrolysis is an old technology that is now a valuable new method of
scale control in evaporative cooling water circuits.
F
rom the time when factory-built package evaporative cooling
towers came onto the market as standard products about 80
years ago, there have been a myriad of methods for preventing
dissolved solids in the supply water from causing scale deposits. It
therefore came as a surprise when browsing the Internet recently
to see that what was currently recommended and offered by
various companies for controlling scaling, was just a single
method: electrolysis — when direct electric current is passed
between two electrodes through an electrically conductive
solution. Electrolysis reactions deposit positive ions (anions) on
the negative electrode (cathode) and negative ions (cations) on
the positive electrode (anode).
All the technical and sales postings displayed by the
companies put high priority on compliance, with both existing
as well as future environmental requirements emphasising that
electrolysis was non-polluting because it was effective without
needing any chemical dosing. Summaries of case histories
accompanied by pictures of electrolysis unit installations and
details of results achieved at sites in countries around the world
were certainly interesting and more credible than much of the
vast amount of pseudo-scientific water treatment claims made
in the past. In fact, a prescient technical paper presented by
Henry A Becker, Jon J Cohen, and Alan D Zdunek was published
by ASHRAE in 2009, detailing how conventional electrolysis
could be applied for anti-scaling in evaporative water circuits
and that it would also provide further benefits in regard to
controlling corrosion, lessening growth of microorganisms, and
a significant reduction in the amount of supply water used by
enabling evaporative water circuits to run at considerably higher
cycles of concentration.
Electrolysis, as a tool to study chemical reactions as well
as produce and purify elements, was used even before the
renowned chemist Michael Faraday gave a formal description
www.hvacronline.co.za
to the term in 1833. In 1785, tin, zinc, and antimony were refined
from their chemical salts using electrolysis powered by an
electrostatic generator devised by Martinus van Marum. Fifteen
years later in 1800, Anthony Carlisle, in partnership with William
Nicholson, was the first to decompose water by electrolysis into
hydrogen and oxygen. Thereafter, chemists continued to make
advances and new discoveries from electrolysis experiments
throughout the nineteenth century. A few of the more notable
successes achieved were:
• 1808 – Potassium, sodium, barium, calcium, and magnesium
were discovered by Sir Humphrey Davy.
• 1821 – Lithium was discovered by the English chemist
William Thomas Brande.
• 1875 – Paul Émile Lecoq de Boisbaudran discovered gallium.
• 1886 – Fluorine was discovered by Henri Moissan.
• 1890 –The Castner–Kellner process was developed for
making sodium hydroxide.
Electrolysis can take place in any liquid that is electrically
conductive. However, because water dissolves many more
substances than any other liquid does, the great majority
of processes utilising electrolysis have been and still are
carried out on water solutions. One of the original processes
for extracting high-grade copper, which is still used today,
is by electrolysing water solutions of copper salts such as
copper chloride in which the cathode of the electrolysis unit
is pure copper. During electrolysis, copper ions migrate and
deposit onto the cathode, enlarging it with pure copper. This
process for recovering copper, and other metals, is known as
‘electro-winning’. Similar electrolysis applications are used to
manufacture a wide range of substances either depositing on
electrodes, precipitating out of solution at electrode surfaces,
or forming gases.
RACA Journal I January 2019
57