Which chemical compound is commonly used to coagulate metals?

The chemical compound that is commonly used to coagulate metals in wastewater treatment is iron salts. Iron salts, such as ferric chloride or ferric sulfate, are effective coagulants that help remove suspended solids and heavy metals from water by promoting the agglomeration of particles. When introduced into the wastewater, these compounds facilitate the formation of flocs, which are larger aggregates of particles that can be easily removed from the water through sedimentation or filtration.

Iron salts work particularly well for metal coagulation because they have a strong positive charge that interacts with the negatively charged particles, allowing for effective binding and removal of metals, especially in challenging wastewater conditions. This makes them a preferred choice in many treatment facilities focused on heavy metal removal.

While other options like aluminum sulfate are also used as coagulants, iron salts are specifically highlighted for their effectiveness in coagulating metals, which is why it is the correct choice in this context.