Everything was fine and dandy on planet Earth until a stargate like portal appeared and connected Earth to a different version of Earth aka Earth2. On this other Earth, humanity evolved differently, their control of chemistry and biology (and subsequent control over the environment) far outpaced what humans on our Earth could have ever dreamed off. As a result, their reliance on technology isn't about the same as us. But that's aside the point. Humans being humans tried peace and decided eventually that peace was never an option.
War eventually broke out nuclear weapons ended up flying. From Earth you have your run of the mill nuclear warheads. Traditional nukes where the radiation doesn't last very long. But then a new class of weapons, dirty bombs. The nasty types that were designed to detonate on the ground, kick up as much contaminated radiation and infect and screw with any biological organisms as radiation normally does. And for a while it works, the humans and bio-organisms from Earth2 suffer as Earth prime lobs nuke after nuke across the gate. But eventually the people and organisms of Earth2 are able to resist the effects of high intensity radiation and contamination.
With this new resistance, they start deploying what are essentially giant suicide bugs that detonate into large explosions and spew radiation (an explosion the size of a decent sized bomb but radioactive). The nasty types you'd get from a dirty bomb. Earth prime and its normal non bio enhanced humans can't keep up with this. Deploying the remainder of nuclear warheads, Earth prime is able to secure a small beachhead on the side of Earth2's gate. A nuclear line in the sand is established, and for a moment the giant suicide bug attacks stop.
The only problem, the high amount of radiation is fatal, and even with some of the best NBC surviving is not possible for only a few moments. Electronics aren't having an easy time as the constant radiation screws with sensors, imaging equipment, radar and electronics. The beachhead and surrounding areas are filled to the brim with contaminated radiation, and that level is only increasing with the constant suicide attacks by the dirty giant bomb bugs as time eventually passes.
What device, chemical reaction, plant etc would allow Earth prime to suck up the radiation or nullify the radiation in an area enough such that they could start a full-blown military campaign on the other side. Synthesizing resistance by figuring out how Earth2 and its organisms can survive the radiation isn't a possibility. This device should be capable of protecting an area from harmful radiation/radioactive contaminants but does and should not protect against things like explosions or gunfire. It's not a force field. Secondly it should be semi transportable in that you can somewhat move it. Even after moving it, radiation shouldn't be re-introduced into the area unless the contaminants naturally make their way back in. Think of it as scrubbing or cleaning the environment.
Tech wise say Earth has made some progress to colonizing the moon by this point (w/ only scientists and a small population of civilians) and manned Mars missions are well underway. Remote/autonomous controlled mining of the asteroid belt is just starting and is in its infancy but returning yields.
Limitations wise, you can't use Earth2's organisms/fauna to create an antidote or somehow make humans magically immune to radiation (use of minerals, or particles from Earth2 is fine), the point is to clear a localized area. Magic is out of the question; the solution has to be somewhat related to science.
Science wise, it doesn't need to be rooted in hard science at all. It just has to sound somewhat believable and grounded in some basic logic/reality such that it makes enough sense to not be outright dismissed.