What is the Difference Between Chlorine and Chlorine Dioxide?

Chlorine and chlorine dioxide are both oxidizing agents used for water treatment and disinfection, but they have distinct differences in their chemistry, effectiveness, and environmental impact. Here are the key differences between the two:

1. Oxidation Capacity: Chlorine dioxide has a higher oxidation capacity than chlorine, making it at least 2.6 times more powerful per ppm according to WHO CT values. Chlorine dioxide can absorb five electrons, while chlorine can only take in two.
2. Corrosiveness: Chlorine dioxide is less corrosive than chlorine because it does not hydrolyze to form an acid.
3. pH Range: Chlorine dioxide is effective at all pH levels below 12, while the effectiveness of chlorine is very pH dependent and is almost ineffective above pH8.
4. By-products: Chlorine dioxide does not react with many organic compounds, meaning it does not produce environmentally dangerous chlorinated organics, such as trihalomethanes (THMs) and haloacetic acids (HAAs). Chlorine, on the other hand, can form these carcinogenic by-products.
5. Effectiveness: Chlorine dioxide is a more effective sanitizer in poor quality water containing high levels of organic matter and other dissolved solids.
6. Biofilm Removal: Chlorine dioxide can remove biofilm, which helps clean tanks and pipes, while chlorine does not have this capability.

In summary, chlorine dioxide is a more powerful, versatile, and environmentally friendly alternative to chlorine for water treatment and disinfection applications. It is effective over a broader pH range, is less corrosive, and does not produce harmful by-products.

Comparative Table: Chlorine vs Chlorine Dioxide

The main differences between chlorine and chlorine dioxide are their chemical structures, oxidation states, and reactivity. Here is a comparison table highlighting the differences between these two compounds:

Chlorine dioxide is a more effective and faster-acting disinfectant compared to chlorine, especially in water with high levels of organic matter and dissolved solids. It also operates in a broader range of pH levels (4 to 10).