A simple method for the mercury-free recovery of fine gold and platinum

摘要

Small-scale gold miners emit annually 500 - 700 tonnes of mercury when amalgamating gold with mercury and subsequent burning. So far, mercury free alternatives have been demanding more skill, time, or capital and environmental costs are not considered in the present gold price. Our objectives are to demonstrate a method marketed by Cleangold~R (US patent granted in July 1999, #5,927,508) by which fine gold can be recovered efficiently and inexpensively, without adding other chemicals than iron grains. Recovery statistics resulted in 90 pencent recovery of gold and platinum in the size range of 50-250 micrometer in diameter in the first pass. Tests with addition of manmade bronze powder (5-10 micrometer) resulted in 60 pencent recovery in the first pass. The surfaces of the gold grains remained unaltered because they were recovered without exposure to mercury, chemicals, or excessive heat. Therefore, inspection with microscope could be a simple, inexpensive analytical method to separate this gold for certification to get a higher market price. In conclusion, the invented sluices are lightweight, inexpensive, and simple to use, thereby saving both money and the environment by making mercury superfluous.