Chitosan works in water treatment primarily as a flocculant and adsorbent, effectively removing suspended solids, heavy metals, oils, dyes, and other contaminants from water. Here’s how it works in detail:
1. Flocculation Process
- Mechanism: Chitosan has a positively charged molecular structure, which allows it to bind with negatively charged particles in water, such as dirt, oil, or heavy metals.
- Aggregation: When chitosan is added to water, its positive charge attracts and neutralizes the charges of these suspended particles. This neutralization causes the particles to clump together, forming larger aggregates or “flocs” that are easier to filter out.
- Removal: Once these flocs form, they can be removed through sedimentation, filtration, or flotation, depending on the water treatment setup. This process effectively removes turbidity, oils, and suspended solids from the water.
2. Adsorption of Heavy Metals and Pollutants
- Chemical Bonding: The amino and hydroxyl groups in chitosan’s structure allow it to bind with metal ions through ion exchange and chelation. This makes it particularly effective for removing heavy metals like lead, mercury, and cadmium from water.
- Enhanced Adsorption Capacity: Chitosan’s structure can be modified (e.g., cross-linking or grafting) to enhance its adsorption capacity, making it suitable for a range of applications where specific pollutants need to be targeted.
- Eco-friendly Advantage: Unlike synthetic resins or coagulants, chitosan is biodegradable and non-toxic, so it doesn’t add harmful chemicals to the treated water.
3. Degradation of Organic Pollutants
- Chitosan can also help degrade certain organic pollutants when used in combination with other agents or under specific conditions (like UV irradiation). This can aid in reducing levels of pesticides, dyes, and other organic contaminants that are otherwise hard to treat.
4. Improving Clarity and Safety of Water
- By binding and removing suspended solids, chitosan improves the clarity of water, making it ideal for use in various applications where high-quality, clear water is essential (e.g., aquaculture, drinking water, and industrial use).
- Chitosan can also remove pathogens and bacteria to a certain extent, contributing to safer water without the need for chlorine or other harsh disinfectants.
Application in Different Types of Water Treatment:
- Municipal Wastewater Treatment: Helps remove contaminants before the water is released back into the environment.
- Industrial Effluent Treatment: Removes oils, heavy metals, and dyes, commonly found in industrial wastewater.
- Drinking Water Treatment: Sometimes used to clarify and purify water for safer consumption.
Overall, chitosan’s natural flocculation, adsorption, and binding properties make it an efficient and eco-friendly choice for water treatment.
