Final answer:
Cadmium hydroxide reduces the efficiency of removing heavy metals because it forms insoluble compounds with them, which can interfere with the precipitation or complexation steps in water treatment processes.
Step-by-step explanation:
The reason why cadmium hydroxide would reduce the efficiency of removing heavy metals is option a) Because it forms insoluble compounds with heavy metals. In water treatment processes, adding substances like sodium hydroxide is used to precipitate and remove heavy metals such as cadmium by forming insoluble compounds like cadmium hydroxide (Cd(OH)2). This precipitation is a useful method for reducing the concentration of soluble toxic metals in wastewater. However, if cadmium hydroxide itself is present, it may form complex ions or insoluble compounds with other heavy metals, thereby reducing the overall efficacy of the heavy metals removal process as it may interfere with the precipitation or complexation steps designed to target other metals.