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Catalytic materials

Catalytic materials in water treatment

Catalytic materials or so called “catalytic loads” is one of the technological method in water purification which provide 3 functions: oxidation, sedimentation and sediment filtration. They are natural or artificial materials that contains oxidation catalyst (mostly manganese dioxide MnO2 ). Such materials are used in water purification from iron, manganese and hydrogen sulphide.

Iron and manganese

Iron and manganese are present in most of underground and surface waters. These impurities give the water a metallic taste/smell as well as color the laundry. Their oxide deposits reduce the pipeline diameter, cause pressure losses in the water systems and in high concentrations they have a negative impact on health.

Hydrogen sulfide

The problem of hydrogen sulfide in the water is also solved with the help of catalytic filter materials. It can be present both in the water from artesian wells as well as in the surface water. The main source of hydrogen sulfide is organic compounds and mineral salts. In natural waters hydrogen sulfide occurs when the water comes into contact with rotten organic residues or mineral salts. High saturation of water with hydrogen sulfide occurs also in underground water where hydrogen sulfide begins to show acid properties and causes the development of sulfur bacteria. Hydrogen peroxide has an unpleasant “rotten egg” smell. Such water is not suitable for both household and industrial use. Hydrogen sulfide reduces the efficiency of water treatment plants (by inhibiting the oxidation of iron).

More information about hydrogen sulfide available here.

What catalytic filter materials are used in water treatment?

The most popular catalytic filter materials are aluminosilicates, dolomite, natural and artificial zeolites and activated carbon. The materials listed in the table cause rapid autocatalytic iron layer formation and bind manganese.

Catalytic materials for iron removal and demanganization

Birm Manganese Greensand Pyrolox MJF 
Color black violet black  black brown
Raw material aluminum silicate glauconite greensand pyrolusite dolomite
Particle size, mm 0.4-2.0 0.25-1.2 0.4-1.5 0.5-1.5
Homogeneity 2.7 1.4-1.6 1.7 1.4-2.0
Particle density, g/cm3 2.0 2.4-2.9 3.8 2.4-2.55
Mass, g/cm3 0.6-0.7 1.4 1.8-2.0 1.4
Maximum Fe content in water, mg/l 4 15 10 50
Fe capacity, g/l 1 0.5-0.64 8 2
H2S capacity, g/l 0 0.4 no data available no data available
pH range 7.0-9.0 6.2-8.8 6.8-8.8 4.5-9.0
Oxidizer О2 KMnO4, KMnO4+Cl2 NaOCl, KMnO4, О2, O3 KMnO4, О2, Cl2, O3
Layer expansion, % 20-40 35-50 15-30 20
Flow rate, m/h (in working mode) 6.0-12.0
Backwash mode (regeneration) 25-30 20-30

 

65-75 35

The main similarity of mentioned catalytic materials is the presence of 3- or 4-valent manganese oxides in their composition. The main advantage: the possibility of regeneration (i.e. to clean the load from accumulated impurities with a reverse water jet).

Catalytic materials for hydrogen sulfide removal

  KDF-85 Centaur
Produced  USA Belgium
Color reddish brown black
Raw material copper-zinc alloy bituminous coal
Particle size, mm 0.15-2.0 0.6-2.4
Particle density, g/cm3 2.74 0.56
pH range of water 6.5-9.0 4.5-10
Maximum H2S content in water, mg/l 5 6
H2S capacity, g/l no data available 90
Layer expansion, % 10-15 30-40
Water flow rate, m/h (in working mode) 36 6-24
Backwash mode (regeneration) 72 24

KDF-85 is a granular catalytic material designed to remove chlorine, iron, hydrogen sulfide and heavy metals from the water. This material is a catalyst of the oxidation-reduction process in which harmful substances are oxidized or reduced and become harmless (e.g. chlorine turns into chloride, hydrogen sulfide into sulfur).

Centaur activated carbon is used to remove iron, hydrogen sulfide and chloramines from the water. Catalytic carbon is granular activated carbon that has been enhanced in the activation process, retaining all the adsorption properties of activated carbon and facilitating chemical reactions.

Catalytic material “Ecomix”

The Ecosoft company has developed a unique catalytic material Ecomix which softens the water as well as remove iron and reduces the amount of organic matter within one filter.

The Ecomix filter material consists of:

  • ion exchange resins for water softening;
  • catalytic sorbent FerroSorb, capable of quickly and efficiently oxidizing iron and manganese ions;
  • catalytic sorbent HumiSorb, which can reduce the color of water by separating humic substances (organic substances of natural origin);
  • quartz sand and light inert material, designed for full washing and filter operation.

Ecomix material is placed in a regular water softening filter. It eliminates plaque on plumbing and scale on heating elements, removes the metallic taste and unpleasant smell of the water.

More information about the catalytic material Ecomix available here.

Disadvantages of catalytic materials

Although catalytic materials have a certain position in the water treatment (they improve water treatment technologies, protects traditional systems and extends their service life), they also have some drawbacks:

  • when using them not only a catalyst is needed but also an oxidizer;
  • they are ineffective against organic iron;
  • they do not work with high iron content (above 10-15 mg/l);
  • a high linear washing speed and high operating water consumption are required;
  • possible entry of manganese into purified water;
  • restrictions may be imposed on the composition of purified water.

Read also: What do the water indicators say?

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