What is KDF？

1. What Is KDF?

KDF is a copper-zinc alloy. It is neither a chemical treatment agent nor a porous material like activated carbon, but rather a granular metal alloy.

It is produced through melting and granulation: copper and zinc are first melted together to form an alloy, which is then made into granules. The golden granules we see inside filter cartridges are KDF.

In water, KDF generates a galvanic reaction to remove residual chlorine and heavy metals. However, two points need to be made clear: its effectiveness depends on several factors, and it is relatively expensive. These two considerations mean it is not the first choice for every application.

Regarding grades and composition, KDF is classified into different grades according to its copper-to-zinc ratio. For example, KDF85 consists of 85% copper and 15% zinc. Different ratios give the material different characteristics and make it suited to different applications.

2. How Is KDF Made?

The basic manufacturing process is straightforward and consists of two main steps:

Step 1: Melting

Pure copper and pure zinc are melted together to form a copper-zinc alloy.

Step 2: Granulation

The molten alloy is then processed using a granulation method to produce the copper-zinc alloy granules we see in the finished material.

In other words, KDF’s quality depends on two things from the outset: whether pure copper and zinc are used, and whether their proportions are accurately controlled. The ratio determines the grade—and ultimately what the material can do.

3. How KDF Works: A “Galvanic Cell” in Water

This is the most important aspect of KDF, and also the one most often made to sound more mysterious than it really is. In fact, it works on the same principle as the galvanic cells taught in secondary-school physics.

The process can be broken down into the following steps:

Two electrodes form. Copper and zinc can generate a galvanic reaction in water. During this process, two electrodes form, just as in a battery: a copper electrode and a zinc electrode, serving as the cathode and anode.

Zinc loses electrons at the anode. The zinc gradually dissolves: metallic zinc, with an oxidation state of zero, becomes zinc ions with a charge of +2 (Zn → Zn²⁺ + 2e⁻), releasing electrons in the process.

Electrons flow toward the copper electrode. The released electrons move to the copper electrode, producing an electric current.

Free electrons are continuously generated. As long as the reaction continues, free electrons are continuously produced.

Free electrons remove strongly oxidizing substances. These free electrons can remove strongly oxidizing substances in water, such as residual chlorine. The residual chlorine is reduced and thereby removed from the water.

Heavy metals are reduced and deposited on the copper electrode. Certain heavy metal ions in the water gain electrons at the copper electrode, are reduced, and form deposits, thereby being removed from the water. This process is particularly pronounced when the water has a certain level of electrical conductivity.

One key condition must be emphasized: both the amount of heavy metals KDF removes and its removal efficiency are directly related to the initial concentration and the water flow rate. In other words, for KDF to work effectively, the initial concentration needs to be lower and the flow rate slower. The more thoroughly the water comes into contact with the filter media, the more completely the reaction can proceed.

4. Factors Affecting KDF’s Performance

Factor Effect

Water conductivity The galvanic reaction requires a certain level of electrical conductivity. If conductivity is insufficient, the reaction cannot proceed effectively.

Initial concentration The lower the initial concentration, the more readily removal can take place.

Water flow rate A slower flow rate allows longer contact time and more thorough removal. If the flow is too fast, there is not enough time for the reaction.

Quantity of filter media A larger quantity of filter media increases treatment capacity and the ability to sustain performance.

As the table shows, KDF is not a filter medium that “automatically works once it is installed.” Its performance depends heavily on operating conditions. This is also why its effectiveness varies considerably between actual products.

5. KDF’s Cost-Effectiveness: A Manufacturer’s Perspective

From our perspective as a manufacturer, our assessment of KDF is fairly measured.

On the one hand, its cost is genuinely high.

It uses pure copper and pure zinc as raw materials and requires several processing steps, including melting and granulation. Neither the materials nor the manufacturing processes are inexpensive, which directly contributes to its relatively high price.

On the other hand, its real-world performance is uncertain.

As discussed earlier, KDF’s ability to remove chlorine and heavy metals depends on factors such as water conductivity, initial concentration, flow rate, and the quantity of media used. Under less-than-ideal conditions, it may fail to deliver the expected performance, even though the cost has already been incurred.

Overall, therefore, we do not consider KDF particularly cost-effective from a manufacturer’s perspective.

To be fair, KDF also has advantages that are difficult to replace: it can address both chlorine and heavy metal removal, and it is relatively resistant to high temperatures. It therefore still has value in certain specific applications. However, when selecting materials and determining their proportions in a product, we need to be clear about whether the money spent on KDF will actually deliver a corresponding level of performance.

6. Summary

KDF is a copper-zinc alloy, produced through melting and granulation, and used as a granular metal-alloy filter medium.

It is classified into different grades according to its copper-to-zinc ratio. For example, KDF85 = 85% copper + 15% zinc.

In water, KDF works through a galvanic reaction: zinc acts as the anode, losing electrons and becoming zinc ions with a charge of +2. The electrons flow to the copper electrode, producing a current. The resulting free electrons remove strongly oxidizing substances such as residual chlorine, while heavy metal ions are reduced and deposited on the copper electrode.

Its effectiveness depends on several factors, including water conductivity, initial concentration, flow rate, and the quantity of media used. A lower initial concentration and a slower flow rate allow it to work more effectively.

Because raw materials and processing are expensive, while performance is constrained by operating conditions, KDF is not particularly cost-effective from a manufacturer’s perspective.