You can use other metals but iron is better because it is less harmful to the environment than other metals. Iron is cheaper too. There are two methods of using iron particles in groundwater remediation.
The traditional way or the most common way of making permeable iron walls (PRBs) is to use iron particles that are manufactured for the construction industry. These micron-sized iron particles are coarse and granular-shaped.
Recently, however, there has been interest in the PRB field in using nano-sized iron particles for cleaning up contaminants in groundwater. Nano-sized particles range in size from 10 to 100 nanometers. Much of this process is similar to the conventional iron wall method for clean up. However, there are a few differences. The nanoparticles particles are so small that you can make slurry solutions and then inject the solutions into the wells. By using this process, you can create an iron wall, but at a much greater depth than the conventional PRB way. This is huge advantage. The downside is that when you inject the iron nanoparticles into the ground, it is not clear how far the particles will move once they are in the groundwater.
Generally, nanoparticles do not move very far, in fact they do not move far enough. You want the nanoparticles to move farther. Researchers are working on ways to make nanoparticles go farther, but if they get too good at this the particles might move to places we don't want them (drinking water supplies, for example). So, we need to do more research to try to figure out if this PRB process poses a potential problem.
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