AbSheild chinese drywall remediation
In another thread where someone was looking for properties with Chinese drywall, a company called AbSheild was mentioned as having a remediation process for this drywall. I looked at this company and their claims.
Disclaimer: I have a degree in Chemistry, among others, but have no inside information or real data about their products of the results. I'm just looking at their web site.
Their claim is: "The method proposed to neutralize the result of residual off-gassing involves the application of absorbent materials in the form of activated organic powders and coatings (solids)." They do this by injecting a powder material into the gaps between studs in interior walls to coat the inside of the sheetrock and by applying a two-layer coating to the exposed side. They claim these materials absorb the gasses emitted by the drywall. They mention "sulfur based off-gassing" and claim the materials absorb the "gas itself and associated odors".
So, is this feasible? Maybe. If the problem is to remove sulfide compounds, and I've found mention of "carbon disulfide, carbonyl sulfide, hydrogen sulfide, and strontium sulfate (trace levels" as the possible culprits in this drywall, then removing them is a somewhat understood process. These compounds, at least the first three, are somewhat common in petroleum and natural gas. Hydrogen sulfide is the most common, and is extremely toxic and dangerous. If these compounds are present, the oil or gas is called "sour" and the process of removing them is called "sweetening". There are several known methods for doing this. All involve passing the stream of oil or gas or other chemical through a vessel containing an absorbent or adsorbent material. Absorbing means something that pulls the gas to be removed into itself, like a sponge. Adsorbing means making the gas stick to the outside, sort of like mist on your glasses when you go from the cold to a hot room (both are weak analogies, this happens at a molecular level.) So, it there is a chemical basis for these claims.
Could you do it with a powder applied inside the wall and a coating on the outside? Not convinced. In a refinery or gas processing plant, these processes are done in a very controlled manner. The content of the oil or gas is reasonably well understood. Other processing steps, in particular water removal (dehydration), may be done first. The specific material to be removed is known, and the absorbent (amines or hydroxides) or adsorbents (promoted alumina or a molecular seive) are tailored to the gas to be removed. The fluid stream is passed through the absorbent or adsorbent material. In these processes, the emitted gases pass through a very thin layer of these materials just once. Once the gasses are out in the room, there is no further effect. Its possible the powder material in the wall cavities could continue to have an effect by absorbing these materials from the captive air in the cavity.
A bigger concern is that these absorbent or adsorbent materials have only a finite capacity. These materials degrade over time, like a sponge filling with water, and must be regenerated (the water squeezed out) or replaced. Since nobody really understands the source of these problem, let alone how much of the problem material is present, I don't see any way to estimate how much of the absorbent or adsorbent material would be needed. The absorbent materials used for this purpose are typically liquids, either naturally for amines, which are derivatives of ammonia or in water based solutions for the hydroxides (e.g, lye). Could be they're using something different than either of these, though. The mention of "activated organic powders" suggests activated charcoal. Nevertheless, my concern is that this may well work for a while, but could end up not working once the absorptive capacity of the material is taken up.
While the sulfur compounds are the source of the problem makes some sense, that's not proven. Certainly those compounds have the "rotten egg" smell often associated with this problem and would cause the metal corrosion. It could be there are multiple compounds involved and this handles the obvious ones, but not all of them.
Now, I'll remind you again, this is nearly pure speculation. There are no details of the chemistry on their web site. They do claim its patent pending, but that's quite a broad term and could refer to a very specific part of the chemistry or the application process. Nevertheless, I'm not convinced this is a robust process that would truly and indefinitely solve the problem. Especially given the problem itself has not been identified.