Pub. 7 2017 Issue 3

9 MINING FOCUS particles in liquid that make the water look cloudy or opaque). Activated carbon removes chemical pollutants that cause the water to smell and taste bad. The two methods are often used together because reverse osmosis does a good job of removing particulates and microorganisms and the activated carbon finishes the purification process by making the water taste better. In addition to reverse osmosis and activated carbon, deionization and distillation are also used. Not all water needs to be purified, but most water needs some combination of filtering and purification. And that is where mining can help. In addition to their many other uses, copper and silver are both important tools for making water safe. Filters contain silver because it is a sanitizer. It can prevent Legionnaire’s disease, for example, which occurs when there is buildup in connections, pipes, and water tanks. As a result of its sanitizing properties, silver ions are being added to community water systems, hospital water purification systems, pools, and spas. But its uses do not stop there. • When medical professionals are treating burns and open wounds, they apply silver sulphadiazine to the damaged areas as the preferred antibacterial treatment. • Medical professionals also use silver in the formof silver nitrate to protect the eyes of babies immediately after they are born. • NASA took advantage of silver’s properties to treat the water used by astronauts during the Apollo flights. Silver was used in the systems for potable water and wastewater, It worked by dispensing silver ions that destroyed bacteria and viruses. Copper offers significant benefits, too. For example, developing countries have started using copper vessels to store drinking water. Why store water in copper vessels? The copper has an antibacterial effect that affects diarrhoeagenic bacteria. During one study, water that had been contaminated with more than six kinds of bacteria was then stored at room temperature in copper pots for 16 hours. The water’s pH increased slightly (from 7.83 to 7.93), but at the end of that time, the bacteria were gone. Why are copper and silver ions and nanoparticles so effective? In water, the ions and nanoparticles have a positive charge. They bond with negatively charged ions on the cell walls of microorganisms. Once there, they affect cell permeability and prevent the cell from taking in the nutrients it needs to survive. In algae, copper and silver attack amino acid radicals that contain sulfur and are located in algae cells. Cells that contain copper and silver ions and nanoparticles are soon put out of commission. Photosynthesis no longer works; neither does regeneration. The cell itself soon disintegrates and dies. Better still, the copper and silver stay in the water for weeks or months and continue to prevent recontamination. Another method for cleaning water involves the use of cathodic ionization. Two electrodes, one with a copper alloy and one with a silver alloy, are placed in a flow-cell chamber that is filled with water. The electrodes are controlled by a microprocessor, which feeds a low-voltage DC current. Electrical current polarity changes every five minutes to keep the wear on the electrodes balanced. Copper and silver have proven indispensable for preventing illness. Both, of course, are valuable mining products whose uses and applications extend far beyond what most people expect. Clean water is critical to raising the standard of living in the U.S. and around the globe, particularly in developing countries. It’s a good thing we have mining to help make that possible. X During one study, water that had been contaminated with more than six kinds of bacteria was then stored at room temperature in copper pots for 16 hours. The water’s pH increased slightly (from 7.83 to 7.93), but at the end of that time, the bacteria were gone.