Cómo se pueden tratar las aguas residuales industriales con filtración con polielectrolitos

Industrial wastewater poses a great threat to ecology and human health. The main concern is how to reduce the harm of industrial wastewater and recover its useful components. This would achieve the double benefit of environmental protection and economy. 

However, outdated methods have disadvantages such as low treatment efficiency, strict environmental conditions, huge amounts of sludge and secondary pollution. The preparation of polyelectrolytes using ultrafiltration technology has advantages such as high treatment efficiency, no phase change, low energy consumption and no secondary pollution.

The principle of polyelectrolyte ultrafiltration

The combination of polyelectrolytes and contaminants occurs through electrostatic interaction and complexation. The technology mainly utilizes the electrostatic attraction between polyelectrolytes and contaminants. The polyelectrolyte, when dissolved in water, ionizes into a polyon and many counterions that have opposite charges to the polyon. Since there are many fixed charges in the molecular chain, an electrostatic field exists around it.  

When the charged contaminant and the oppositely charged polyelectrolyte are mixed, the diameter of the contaminant widens. It is easily retained by the ultrafiltration membrane. Although water and some unbound contaminants can pass through the membrane, most contaminants are effectively separated from the wastewater. Of course, in the wastewater, metal ions form complexes with the functional groups of the polyelectrolyte.  

Either by electrostatic attraction or by coordination bonds, metal ions bind to the polyelectrolyte, causing it to widen in diameter and be retained by the ultrafiltration membrane. This is done to remove heavy metals from the water.

Types and applications of polyelectrolytes

Based on the properties of the molecular chain groups, polyelectrolytes can be divided into three types:

cationic polyelectrolytes
anionic polyelectrolytes
amphoteric polyelectrolytes
For different treatment objects, polyelectrolytes should be chosen based on the contamination of the wastewater. This helps to determine the specific circumstances of the object.

What are the factors that influence polyelectrolyte ultrafiltration?

1. The concentration of polyelectrolyte

As the polyelectrolyte concentration increases, the number of binding sites that can bind contaminants in a unit volume of solution increases, and the rate of contaminant removal by polyelectrolyte ultrafiltration increases. 

Therefore, the polyelectrolyte concentration should be appropriately considered. The contaminant removal rate and permeation flux are the best values ​​that can maintain a high permeation flux while meeting the removal rate needs. 

2. The pH value of industrial wastewater. 

The pH value is one of the most crucial factors affecting the interaction of polyelectrolyte and metal cations. This influences the complex process of metal ions and polyelectrolytes. Different metal complexes have varying sensitivity to pH. Compared with Hg2+, the change in pH significantly affects the rejection of Cd2+, and this sensitivity occurs mainly in the pH range 5-6.

3. The influence of coexisting ions 

In the polyelectrolyte structure, the coexisting ions compete with the target ions for binding sites, which affects the combination of the target contaminants and the polyelectrolyte. The second fact is that the presence of salt ions increases the ionic strength of the solution and the polyelectrolyte. 

The electrical double layer is compressed, which reduces the electrical potential. This reduces the electrostatic interaction between the contaminants and the polyelectrolyte, leading to a decrease in their retention rate.

Methods for recycling polyelectrolyte

One of the methods is to improve the recovery and utilization of polyelectrolytes. A large amount of polyelectrolyte is used in the preparation of polyelectrolytes. Therefore, the operating cost is high during continuous operation. In this case, it is directly discharged into the environment, which is likely to cause secondary pollution. 

Therefore, to recycle polyelectrolytes, reduce operating costs and minimize the risk of secondary pollution. Polyelectrolyte recovery methods mainly include 

• acidification ultrafiltration
• ultrafiltration with salt addition
• electrolytic recovery
• combination of these three methods.

Conclusion

Water treatment is an essential process that requires constant innovation to solve global challenges related to water quality. The preparation of polyelectrolytes is one such advancement in water treatment solutions. 

Keiken Engineering has been a leader in unlocking the potential of polyelectrolytes to improve water treatment processes. Contact us today if you need help getting clean, safe water to your home or business.