Environmental uses

Chlorinated hydrocarbons are major pollutants of groundwater. Recent research at Rice University's Centre for Biological and Environmental Nanotechnology has revealed that bimetallic gold-palladium nanoparticles provide an active catalyst to break down trichlorethene (TCE), one of the most common and poisonous groundwater pollutants. TCE has been linked to liver damage, impaired pregnancy and cancer.  This nanomaterial opens up tremendous opportunities in groundwater clean-up. In other work, researchers from the Indian Institute of Technology, have proven that gold nanoparticles, incorporated into a point-of-use water purification device, can be effective in the capture and removal of halocarbon-based pesticides from drinking water. Development of this technology is being supported by the World Gold Council through its GROW Programme.

See http://www.ivanhoe.com/science/story/2008/04/418a.html for video news report on this technology

Mercury Control
The US is relying increasingly on the use of coal to produce electrical power and significant levels of mercury occur in the effluent from these power plants. Control of mercury, which has been linked to Alzheimer’s disease and autism, is expected to be achieved in the US by imposed limits on mercury emissions from coal-fired boilers in the utilities industry. One method to increase mercury removal is to introduce a catalyst to enhance the oxidation of mercury and gold catalysts are proving to be very promising. Full scale trials are currently underway, see National Energy Technology Laboratory for more information. Another major cause of mercury pollution, particularly in China, is from contamination arising through the manufacture of the commodity chemical vinyl chloride monomer, used the manufacture of PVC. World Gold Council is supporting research aimed at developing an industrial gold-based catalyst that could be used in a cleaner version of this manufacturing process, significantly reducing mercury contamination from these plants.

Diesel Emission Control
The recent announcement by U.S. company Nanostellar that they have developed an automotive pollution control catalyst for diesel engines that contains gold, as well as the traditional platinum and palladium ingredients, is a major step-forward in cost effective emission control. Through World Gold Council, the gold-mining industry is supporting the development of this technology. Independent testing of Nanostellar’s NS Gold™, has shown that NS Gold™ increases hydrocarbon oxidation activity by 15-20 percent at equal precious-metal cost. A tri-metal formulation of gold, platinum, and palladium, NS Gold™ allows the proportions of each metal to be adjusted to help catalyst systems engineers meet engine-specific performance targets and stabilize the overall cost of diesel catalysts, despite fluctuations in the price of precious metals. For more information visit www.nanostellar.com

'Green' Chemistry
Green chemistry, also called sustainable chemistry, is a chemical philosophy encouraging the design of industrial chemicals and processes that reduce or eliminate the use and generation of hazardous substances. The use of gold as a catalyst has a major role to play in green chemistry.

For example, most industrial oxidation processes tend to use chlorine or organic peroxides. The chlorine processes produce large amounts of chloride salts and significant amounts of chlorinated organic by-products. The disadvantage of organic peroxides is their expense. It is fair to say that the chemical industry would be transformed if selective oxidation of hydrocarbons could be achieved efficiently using cheap and clean oxygen from the air. Recently a team led by Graham J. Hutchings, professor of physical chemistry at Cardiff University, in Wales, has shown that gold nanoparticles supported on carbon activate molecular oxygen in air to convert alkenes to partial oxidation products such as epoxides at atmospheric pressure and temperatures of 60–80 °C (Nature 2005, 437, 1132). This advance of ‘greener’ methods for oxidation catalysis using gold is a very important development.

As global demand and prices for petroleum-based feedstocks continue to rise, chemists are being challenged to devise processes that use biomass-derived feedstocks. In one of the latest developments, workers of the Center for Sustainable & Green Chemistry at the Technical University of Denmark, in Lyngby, have come up with a gold-catalyzed procedure for selective oxidation of the biomass-derived platform chemicals furfural and hydroxymethylfurfural to form their respective methyl esters. These chemicals are used for flavour and fragrance applications, in plastics and potentially as industrial solvents.

Fuel cells 
Fuel cells using hydrogen fuel are a promising clean energy source for automobiles, homes, and mobile devices. At present, platinum is generally used as a catalyst in the fuel cell. However, platinum is an extremely expensive precious metal, therefore, an important R & D theme in the fuel cell industry is reduction of material cost by minimizing use of platinum. In 2008, leading Japanese manufacturer Hitachi Maxell announced development of a new catalyst based on gold-platinum nanoparticles - see http://www.maxell.co.jp/e/release/20080327.html for more information. This success represents a large step closer to the practical use of fuel cells for applications requiring large current, such as power sources for automobiles and homes.