Which of the following is not a practical method for removal of cadmium?

Reverse osmosis is identified as not being a practical method for the removal of cadmium primarily due to its technical limitations and cost-effectiveness in certain situations. While reverse osmosis is generally effective in removing a wide range of contaminants from water, including heavy metals, its application for cadmium removal may not always be feasible.

The process of reverse osmosis involves pushing water through a semi-permeable membrane, which can remove various dissolved substances, including salts and some metals. However, treating water that is high in cadmium concentrations with reverse osmosis can be quite expensive in terms of both the initial capital costs of the equipment and the ongoing operational costs, such as energy and membrane maintenance.

In contrast, the other methods evaluate the removal of cadmium more effectively or economically in certain scenarios. Ion exchange specifically targets heavy metals and can effectively reduce cadmium levels from water through the exchange of ions. Lime softening is another method that can be used, especially in groundwater treatment, where it helps to precipitate cadmium and other metals by adjusting pH levels. Iron coagulation involves adding iron salts, which can bind to cadmium and allow for its removal through sedimentation, making it a direct approach to treat contaminated water.

Overall, while reverse osmosis