I can only offer one idea.  I'm not familiar with the heap leach process, but do know that copper is a not very reactive with most chemicals. You may want to try PEG 10,000 (Polyethylene glycol 10,000 molecular weight) or one of the polysulfones that are used in industrial detergents. I'm not sure what cost you can tolerate or how low the pH may be, but these agglomerating agents are used in modestly low pH environments (about 4). We used to use PEG for detergents to prevent dusting.