Which resin is commonly used in recovering gold through ion exchange?

The commonly used resin for recovering gold through ion exchange is cation exchange resin. These resins are specifically designed to attract and retain positively charged ions (cations), which include various metal ions such as gold. When a solution containing gold cations is passed through a cation exchange resin, the resin binds to the gold ions, allowing for their separation from the rest of the solution.

Cation exchange resins have a high affinity for specific metal ions, which makes them effective for metal recovery processes, including the extraction of noble metals like gold. The process typically involves leaching gold from ore with a cyanide solution, followed by treatment with the cation exchange resin, resulting in the capture of gold ions.

The other options, such as anion exchange, polymer resin, and silica gel, do not perform the same function as cation exchange resins in gold recovery. Anion exchange resins target negatively charged ions, which make them unsuitable for extracting gold in its cationic form. Polymer resins can serve various purposes in filtration and separation processes but are not specifically designed for metal recovery like cation exchange resins. Silica gel primarily serves as a drying agent and does not have the ion exchange properties necessary for recovering metals like gold.