Which of the following would not be used as a coagulant?

Sodium hypochlorite is not used as a coagulant in water treatment processes. Instead, it is primarily employed as a disinfectant. Its main function is to kill bacteria, viruses, and other pathogens in water, making it safe for consumption. The mechanism by which sodium hypochlorite operates involves oxidation, which is distinct from the coagulation process.

In contrast, coagulants are substances used to facilitate the aggregation of particles in water, helping to remove suspended solids and improve water clarity. Black alum (aluminum sulfate), chlorinated copperas (ferrous sulfate), and ferric chloride are all effective coagulants. They work through the addition of positive ions, which neutralize the charges on suspended particles, allowing them to clump together and settle out of the water. Each of these chemicals plays a critical role in various water treatment applications, making them appropriate choices as coagulants.