Within the water treatment industry, there are a number of media that incorporate MnO2. Following is a brief discussion of some of media utilizing this catalyst, which range from pyrolusite media with a high percentage of MnO2 to lightweight manufactured media with MnO2 coating. High-MnO2 concentration pyrolusite ore has MnO2 contents to 70-85 percent. This category of media is heavy, weighing around 110-120 pounds per cubic foot. They have a specific gravity (relative density) of 3.5 to 3.8 (see Figure 2). In Figure 1, one sees that it has sheared surfaces and flattened multiple sides. It is solid, high-concentration MnO2 material all the way through the ore. To manufacture it into a usable media, it is broken into smaller pieces ranging from 8 x 20 to 20 x 40 standard US mesh size. This means that the larger material is 0.09 inches (8 mesh, 2,380 micron, 2,380 millimeters.) x 0.03 inches (20 mesh, 841 micron, 0.841 millimeters.) The smaller material is 20 mesh x 0.016 inches (40 mesh, 420 micron, 0.420 millimeters.)5 Having irregular flat surfaces and sharp edges makes the ore an excellent filtration medium.
There are several popular media on the market that use a host material and coat it with manganese dioxide. These products are designed to be lighter and require a lower backwash rate. Greensand is an industry standard going back decades. It is a mined zeolite that receives an MnO2 coating. Note: Due to diminishing supplies, companies are manufacturing replacements for greensand. These manufactured media, like greensand, require regeneration with potassium permanganate (KMnO4) to retain their MnO2 properties. There are numerous media options on the market that are manufactured with MnO2 coatings. Some require regeneration to remain active and some use other technologies along with an MnO2 coating to create a catalytic action. These products weigh in the range of 35 to 85 pounds. They have specific gravities from 2 to 2.9 and backwash at 10 to 12 gpm/ft2. The mesh sizes for these products are in the range of 18 x 60 to 12 x 50.