Chemical precipitation of metal wastes in the metal finishing industry is often achieved using:

In the context of treating metal wastes in the metal finishing industry, chemical precipitation using hydroxide is a common and effective method to remove metals from wastewater. The process involves adjusting the pH of the wastewater to a level where metal ions, such as lead, copper, or cadmium, are converted into insoluble hydroxide compounds. These compounds can then precipitate out of solution, allowing for easier removal through sedimentation or filtration.

Hydroxide precipitation is particularly advantageous because it can effectively address a wide range of heavy metals. The process is relatively straightforward and economically viable, making it a preferred technique in many wastewater treatment facilities. Additionally, managing pH levels to facilitate this precipitation not only helps to remove toxic metals but also aids in minimizing the overall environmental impact of the treated effluent.

In contrast, other chemicals listed may not serve the same purpose effectively: chlorine is generally used for disinfection rather than precipitation, aluminum sulfate is primarily a coagulant used to remove suspended solids, and phosphate can sometimes lead to secondary pollution concerns, particularly in aquatic environments, rather than directly precipitating metals. This context underlines why hydroxide is the appropriate choice for the given application in metal finishing wastewater management.