KDF is the name of an extremely expensive and efficient latest water treatment filter material invented by American scientists. Because it is efficient and expensive, it is commonly known as water gold, which means it is more expensive than gold.
It performs water treatment work through micro-electrochemical oxidation-reduction reaction Redox. When in contact with water, the two metals in the alloy form countless small galvanic battery systems on a submicroscopic scale. This material It has strong reaction ability and extremely fast reaction speed in water, and can remove up to 99% of chlorine in water and metal ions and compounds such as lead, mercury, nickel, and chromium dissolved in water. It has an excellent effect on inhibiting the growth of bacteria, fungi, dirt and algae. Used in pretreatment, main treatment and wastewater treatment equipment. KDF improves or replaces existing technologies, which can greatly extend the life of the system, reduce heavy metals, microorganisms, and dirt, reduce the total cost, and reduce system maintenance.
KDF has been awarded 14 patents in the United States alone. It is currently the safest and most expensive water treatment filter material, and its overall water purification effect is better than any other technology currently available.
It has six major functions:
◆ Remove strong oxidants (residual chlorine)
KDF has strong reducing ability and can remove various strong oxidants in water , especially effective against residual chlorine. KDF is composed of two different metals, copper and zinc. When in contact with water, the copper with positive potential in the alloy becomes the cathode, and the zinc with negative potential is the anode, forming a primary battery. The zinc anode loses electrons during the reaction, generating zinc ions into the solution. The reduction reaction of free chlorine occurs on the copper cathode without dissolution of metallic copper. Water and residual chlorine become the final electron acceptors, and at the same time generate hydrogen ions, The total reaction formula of hydroxide ions and chloride ions is as follows:
Zn HOCl H2O 2e—Zn2 Cl- H 2OH-
Other oxidants in water, such as ozone, bromine, iodine, etc., react with Similar redox reactions can occur upon contact with KDF.
◆ Removal of heavy metals
KDF treatment media can remove a variety of heavy metal ions in water, such as lead, mercury, copper, nickel, cadmium, arsenic, antimony, aluminum and many other soluble heavy metals ions, their removal is accomplished through displacement reactions and physical and chemical adsorption reactions. The mechanism of KDF to remove heavy metal ions is as follows: metal ions are adsorbed on the surface of KDF treatment medium and undergo a displacement reaction with zinc in KDF. The generated metals are either adsorbed on the surface of KDF or enter the KDF lattice, thereby binding toxic heavy metal pollutants. on KDF. For example, lead ions dissolved in water are reduced to insoluble lead atoms and adsorbed on the surface of KDF media. A similar reaction occurs between mercury ions and KDF. X-ray diffraction studies have found that the removal of mercury results in the formation of copper-amalgam. The chemical reaction formula for KDF to treat heavy metal ions is as follows:
Zn/Cu/Zn Pb2 →Zn/Cu/Pb Zn2
Zn/Cu/Zn Hg2 →Zn/Cu/Hg Zn2
When the pH of water increases, metal ions hydrolyze to form metal hydroxide precipitation, which can also remove metal ions.
◆ Removal of hydrogen sulfide
When using membrane method for water treatment, if groundwater is used as the water source, hydrogen sulfide may be present in the water. If hydrogen sulfide is oxidized into sulfur, it will pollute the filter. On the membrane surface, the KDF filter medium has the function of removing hydrogen sulfide. The generated copper sulfide is insoluble in water and can be removed during backwashing of the KDF medium. The chemical reaction formula is as follows:
Cu/Zn H2S → Cu/Zn CuS H2
2H2 02 →2H20
◆ Reduce suspended solids
The average particle size of the KDF treatment medium is approximately 60 mesh, and the smallest particle is approximately 110 mesh. It can also play the role of physical filtration to remove suspended substances. Usually KDF filter media can effectively remove particles with a diameter of less than 50 μm.
When water pipes made of steel materials corrode, iron oxidizes to form FeO colloid. When FeO comes into contact with KDF (KDF), an oxidation-reduction reaction can also occur. FeO eventually forms Fe2O3 solid and precipitates on the surface of KDF. , they can be removed by backwashing. The chemical reaction formula is as follows:
Zn FeO = ZnO Fe
2Fe 3O2 = 2Fe2O3
◆ Reduce mineral scaling
The effect of KDF treatment medium on calcium carbonate scale has two aspects.
★ On the one hand, according to the relationship between pH, carbon dioxide concentration and calcium carbonate solubility, when carbon dioxide is removed from the solution, the pH value increases, thus reducing the solubility of calcium carbonate. KDF also increases the pH value of water through electrochemical reactions and reduces the solubility of calcium carbonate, making calcium carbonate scale easy to precipitate.
★ On the other hand, due to the dissolution of zinc ions in the KDF treatment medium, the zinc ion content in the water has increased. The presence of zinc ions in the water can change the crystal growth mechanism of scale, making the calcium carbonate scale in the water Precipitation occurs in the crystalline form of aragonite, forming soft scale on the walls of the container, rather than crystallizing into calcite-type hard scale. Someone once studied the impact of the presence of impurities in water on the growth of calcite crystals. The study found that even when the concentration of zinc ions is very low, it can prevent the formation of calcite crystals.
Tests can further prove that KDF treatment media prevents the formation and accumulation of mineral hard scale, mainly preventing the crystallization of calcium carbonate in the form of calcite. Crystallographic studies using scanning electron microscopy and X-ray diffraction prove that the hard scale produced in water without KDF treatment is the crystallization of some relatively large, regular-shaped needle-like calcium salts and magnesium salts. These salts are hard and It has low solubility and a network structure. It is glass limestone scale. The scale formed in the water treated by KDF fundamentally changes the form of calcium carbonate (magnesium) crystal. The scale shape becomes relatively smaller and the appearance is flat and round. Both granular and rod forms are composed of non-hard powdery ingredients that do not adhere to metal, plastic or ceramic surfaces and are easily removed by physical filtration.
◆ Inhibit microbial reproduction
KDF treatment medium controls the growth and reproduction of microorganisms not through one mechanism, but through several mechanisms, which are achieved through the individual or synergistic effects of each. Inhibit the effect of microorganisms. The main mechanisms include: changes in redox potential, formation of hydroxide ions and hydrogen peroxide, dissolution of zinc in the medium, etc. Under normal circumstances, when KDF treatment medium is used as a pretreatment method for reverse osmosis membranes, it can inhibit the reproduction of bacteria, algae and other microorganisms, thus preventing microorganisms from damaging the membrane.
★ Changes in redox potential
When water passes through the KDF treatment medium, its redox potential changes from +200mV to -500mV. Under normal circumstances, various types of microorganisms can only Growing under a specific redox potential, large changes in potential can destroy bacterial cells, thus controlling the growth of microorganisms. However, the change in the redox potential of water is very small. To use KDF to control bacteria, the bacteria must be in direct contact with KDF. The inhibitory effect of KDF on bacteria mainly occurs on the contact surface between KDF and water, so the change in redox potential alone cannot Complete control of microorganisms.
★ Hydroxide ions and hydrogen peroxide
KDF will produce hydroxide ions and hydrogen peroxide during the oxidation of ferrous iron to trivalent iron, which can Inhibit those microorganisms that can survive at low oxidation potential but are sensitive to hydrogen ions and hydrogen peroxide. However, hydroxide ions and hydrogen peroxide have short lifespans and only have high reactivity during the filtration process, inhibiting microorganisms. The effect is more obvious, and the residual effect in the outflow water is relatively small.
★ Control of microorganisms by zinc ions
The zinc released from the KDF treatment medium has an obvious control effect on microorganisms. Zinc can prevent the synthesis of enzymes, thereby affecting the normal growth of organisms. , to achieve the purpose of inhibiting microbial reproduction. In addition, KDF medium controls algae growth by preventing chlorophyll synthesis. The presence of zinc ions essentially reduces the organism's ability to produce food from photosynthesis, which will significantly affect the growth of bacteria.