How does mno2 work as a catalyst

None of it magic. Everyday, these applications go into service and everyday, technicians applying the treatment have no real idea how it actually works. It just works, it is magic. Reality check: people put gas in their car and drive it down the road without any knowledge of combustion or coefficients of friction. This works because they only wish to drive from point A to point B. This does not work for the mechanic asked to fix the vehicle. People wanting clean water to flow from the faucet do not really care how it happens.

Catalytic precipitation, particle adsorption and mechanical straining are not topics that interest users. This is not a luxury afforded a water treatment specialist. Manganese dioxide MnO2 is an inorganic compound. It is a black to brown-colored material that occurs naturally as the mineral pyrolusite see Figure 1. In addition to water treatment, MnO2 has many uses, including but not limited to the manufacture of batteries, beverage cans, agricultural pesticides and fungicides and electronic circuitry.

Manganese dioxide technology is one of the most commonly used and least understood applications for removing iron, manganese, hydrogen sulfide, arsenic and radium. Read along and discover that MnO2 is not magic dust, but a very helpful catalyst used to improve water quality in applications from private wells to large municipalities. History of manganese dioxide The use of manganese dioxide goes back 17, years to the upper Paleolithic period when Stone Age men used it as a pigment for their cave paintings.

The Spartans of Ancient Greece used MnO2 in their steel making, thus creating weapons superior to those of their enemies. The Egyptians and the Romans used manganese ore in glass making to give the glass pink, purple and black tints. In the midth century, manganese oxide was a main ingredient in the manufacture of chlorine. In , a German researcher noted that manganese increased the hardness of iron, without compromising its flexibility or strength. The battery industry is the second largest consumer of manganese today.

The uses for MnO2, like many of the technologies used today in water treatment, have a long and storied history. What is a catalyst? A catalyst is best described as something that drives change. A skier at the top of a grassy ski slope in the summer can slide down the slope and eventually get to the bottom of the hill. At the top of the hill, the skier has the potential, over time, to get to the bottom of the slope.

The same skier will have an easier time getting to the bottom of the slope in the winter when the hill is covered in snow, which accelerates the potential. The snow is the catalyst. It allows the skier to move faster and accelerates the act of reaching the bottom.

Abraham Lincoln and the Civil War were both catalysts for change in US policies on secession and slavery. In chemistry, a catalyst causes or accelerates a chemical reaction without itself being affected.

In water treatment, MnO2 provides filter media with a catalyst. Manganese dioxide creates a catalytic effect in the chemical oxidation-reduction reactions necessary to remove iron, manganese, H2S, arsenic and radium. Media using MnO2 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 percent. This category of media is heavy, weighing around pounds per cubic foot. They have a specific gravity relative density of 3. 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. The smaller material is 20 mesh x 0. 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. The mesh sizes for these products are in the range of 18 x 60 to 12 x Operations All MnO2 media have specific conditions of operation for proper application. Knowing these conditions and closely following the operation instructions makes for a quality system. Figure 2 gives an overview comparison of the MnO2 media discussed. While some MnO2 media are heavier and requires higher backwash rates, they do not necessarily use more total gallons of water for backwashing and rinse.

The difference is that pyrolusite media can clear the bed of loading in four to five minutes. In addition, pyrolusite does not require regeneration with KMnO4. A byproduct of removing manganese is the removal of radium. This happens because radium bonds readily to manganese. To assist in the removal of radium, some systems use the addition of hydrous manganese oxide HMO to increase co-precipitation of radium during the manganese removal process.

HMO is added to the water upstream of the filter to attract radium to the manganese oxide precipitates. These manganese precipitates, which hold radium, are filtered from the water along with existing iron and manganese.

Through HMO co-precipitation, radium is strained from the water as a solid then washed to drain when the filter backwashes. Systems utilizing co-precipitation through HMO require regular backwashing. The backwash water from this method of treatment contains radium-bearing waste. The table describes three common catalysts. Notice that these catalysts are transition metals or compounds of transition metals.

A catalyst provides an alternative reaction pathway that has a lower activation energy than the uncatalysed reaction. This does not change the frequency of collisions. However, it does increase the frequency of successful collisions because a greater proportion of collisions now exceeds this lower activation energy. The effect of a catalyst on the activation energy is shown on a chart called a reaction profile.

This shows how the energy of the reactants and products change during a reaction. An enzyme is a biological catalyst. Enzymes are important for controlling reactions in cells. They are also important in industry. The use of enzymes allows some industrial reactions to happen at lower temperatures and pressures than traditionally needed.

Yeast is a single-celled fungus. The enzymes in yeast are used to produce wine, beer and other alcoholic drinks by fermentation of sugars. Catalysts A catalyst is a substance that: increases the rate of a reaction does not alter the products of the reaction is unchanged chemically and in mass at the end of the reaction Only a very small mass of catalyst is needed to increase the rate of a reaction.