As you probably guessed, from the title diatomaceous earth is a quick and easy solution to dispatch those unwelcome guests quickly and efficiently. Diato-what? I thought you might say that, which is why I've come prepared to explain. I could throw a bunch of mumbo jumbo and talk about algae and crystalline and other scientific stuff. The quick and easy home mixture to get rid of ants is just to use baby powder... yes, baby powder. It's pretty effective - ants come into contact with it and it dries them right up. Poof - ants be gone. Wait - use a vacuum cleaner and then the process of killing ants will have been completed.
Now if you do decide to buy straight up diatomaceous earth from your local store, there are some potential health risks to be aware of. It's still a natural solution, but not as people friendly as baby powder. Handle it with gloves because that stuff will dry your hands out quickly. You may also want to use a mask as the powder is fine and could do damage if you inhale too much of it... especially if you're using the industrial version because it has a highly crystalline form of silica that result in sharp edges.
Now if you're trying to treat a large area, such as a garden or outside around the house, you're probably not going to sprinkle baby powder everywhere... that's a lot of baby powder. I recommend purchasing Concern Diatomaceous Earth - Crawling Insect Killer
You asked how to get rid of ants naturally, and I have answered. Stay tuned for more natural ways to get rid of ants!