Ferric Chloride

The primary use of ferric chloride is to remove impurities in water and for wastewater treatment. The second-largest application is in the production of printed circuit boards (PCBs). In 2010, global capacity was nearly 2 million metric tons. Growth is forecast at almost 3% annually during 2010–2015, although Asian growth (excluding Japan) is forecast at a much higher annual rate of 6.7%.

The following pie chart shows world consumption of ferric chloride:

In Western Europe, ferric chloride is used mostly as a coagulant for sewage treatment and potable water production. Growth in consumption in Western Europe is driven by stricter EU legislation for clean water standards in both the municipal and industrial sectors. Demand for ferric chloride has been buoyant in countries like the United Kingdom, France and Belgium and in Mediterranean countries because they are linked to EU norms for phosphorus removal.

Ferric chloride is used in many industries in China. The major applications include use as a purifying agent in water supply and as a coagulant in municipal and industrial wastewater treatment, use as an oxidant in indigo blue dyestuff production and as an etching medium in producing printed circuit boards (PCBs). Ferric chloride consumption for water treatment will continue to be the largest market in China, where wastewater is treated and recycled extensively for industry use and farm irrigation. Chinese PCB production has increased rapidly because the major PCB producers from Japan, Taiwan and the Republic of Korea are shifting PCB production to China.

U.S. ferric chloride producers tend to have a regional, rather than a national outlook, because transportation costs are significant. More than 80% of all ferric chloride is sold in municipal bids, with 65% sold for municipal wastewater applications, and 18% for potable water treatment applications. Industrial water treatment applications account for 9% of consumption, with the remaining 8% sold in non–water treatment applications, as electronic and photographic etchants, in metal surface treatment, and as catalysts.

In Japan, there are two major applications for ferric chloride. One is water treatment and the other is etching for printed circuit boards (PCBs). In 2009, ferric chloride consumption declined drastically as a result of the global economic crisis that began in late 2008. Responding to global and Japanese economic recovery, ferric chloride consumption recovered in 2010. However, Japanese consumption will not return to the levels of the mid-2000s, because of decreasing domestic demand for PCBs and water treatment.

Ferric chloride's rapid hydrolysis in water makes it an ideal flocculating and precipitating agent. The ferric hydroxide (Fe[OH]₃) produced forms flocs (small clumps or tufts) that adsorb suspended particles of various materials (e.g., colloids, clays and bacteria). The clumps, with the adsorbed matter, are then allowed to settle out for removal. Ferric chloride forms precipitates with hydrogen sulfide (H₂S), phosphate (PO₄), arsenic as arsenate (AsO₄) and hydroxide alkalinity (OH).

Ferric chloride is one of the few water treatment chemicals that can sequester odors. Unlike hydrogen peroxide and potassium permanganate, the ferric chloride (and sulfate) reaction is irreversible.

Ferric chloride competes with ferric sulfate, aluminum salts such as aluminum sulfate (alum), sodium aluminate, polyaluminum chlorides, and organic polymers in the treatment of raw water and wastewater. The decision to use ferric chloride is highly dependent on location to the source, as transportation costs can be a large part of the delivered cost.

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