History of resins in Gold Recovery

Ion exchange consists is exchange an ion by other one. When the exchange involves cations the process is named cationic exchange and when involves anions is named anionic exchange [1]. At the beginning ionic exchangers were only employed in small scale in the water treatment. The first exchangers were natural materials named Zeolites. In 1940, its application field was expanded until became one of the most important operations in the chemistry and metallurgy. For that, was necessary obtain synthetic materials because natural ones had serious problems. The synthetic exchangers are named resins.

The first ion exchange resin was development in England by Adams and Holmes during their free time. The worked done by Adams and Holmes was followed and studied by researches from The United States, Germany, and Russia. The development effected was very fast and the resins fabricated were of phenolic type. The first ion exchange resin was obtained from the reaction of phenol, formaldehyde and a polyamine. These resins were discarded because its time of life was very limited, and also had a loading capacity very low.

After the World War II, there was a big effort of many researches in the world with the common idea of improving the application of synthetic materials. As result, were obtained resins with high loading capacity, more versatile, and more durable.

The age of synthetic resins as ion exchangers started in 1935. The first resin was developed with the synthesis phenol-formaldehyde. In 1938, The Rohm and Haas Company solicited a patent in The United States for a new type of resin named Amberlite. In 1940, appeared in the market his first commercial phenol-formaldehyde resin which was similar to the one obtained by Adams and Holmes but stronger. In 1944, the same company fabricated a special type of resin to be used in chemical analysis. For the same time, The Permutit Company and Dow Chemical Company offered a similar resin to the developed by Rohm and Haas Company. In 1948, appeared a new and more complete group of Amberlite resins. This new type of resins comprised cationic and anionic resins for specific applications such as water treatment, copper-zinc separation, pharmacy, etc. The development of these resins started with the synthesis sulfonic styrene divynil benzene co-polymers.

Nowadays there are new efforts for obtaining new synthetic products for specific use and some of them are in the market, but there new and more questions that need to be answered.