Ion exchange in metal-plating industries is primarily used for:

Ion exchange is a crucial process in metal plating industries, primarily utilized for by-product recovery. In these industries, ion exchange processes can help recover valuable metals from wastewater streams that can contain precious metals or other ionic species. By carefully selecting resin materials, metal ions can be exchanged for other ions, allowing businesses to extract and recover these metals rather than letting them go to waste. This not only conserves resources but also can result in additional revenue streams through the recovery of valuable materials.

The other options do not address the primary application of ion exchange in the context of metal plating. Waste discharge, while relevant to wastewater management, does not harness the potential of ion exchange for recovery. Energy generation does not typically align with the ion exchange process, and while water softening does utilize ion exchange techniques, it is not the main focus within the metal-plating sector. The emphasis on by-product recovery highlights the economic and environmental benefits of efficient resource management in industrial processes.