Coagulants are used for treatment of all kinds of water
Coagulation is the oldest known water treatment method
In industry, coagulants are frequently used for water treatment
In drinking water production, coagulants remove particles, humic substances and colour
Coagulants produce healthy and enjoyable drinking water
Coagulants are used for treatment of all kinds of water

Inorganic coagulants are used in two critical parts of the paper production process: sizing and retention.

Sizing
Sizing controls the amount of liquid the cellulosic fibres in paper can absorb. Appropriate sizing regulates the amount of ink or water that can penetrate into the paper. Without it, our printed papers would end-up a soggy mass.
A combination of aluminium salts and organic compounds have been used to control the amount of sizing in paper since the 1800s. Aluminium sulfate was initially used, but it was replaced in the 1990s by poly aluminium chloride (PAC).

Retention
Retention is a papermaking term which describes the process of separating fibres from water to form a paper sheet. Good retention is essential for economical and quick paper production.
Retention is one of the most controlled parameters in the papermaking process. Improving retention reduces the amount of papermaking compounds, fibres and fillers in the waste water and improves profitability.
To increase fibre and filler retention, aluminium salts, sodium aluminate (SAL) and poly aluminium chloride (PAC) are used. Aluminium salts enhance the effect of other process chemicals (for example, poly-electrolytes) and remove unwanted anionic trash.

Applications

Other Applications
In addition to their role as inorganic coagulants, aluminium and iron salts are used in many other applications.
Paper Industry
Inorganic coagulants are used in two critical parts of the paper production process: sizing and retention.
Drinking Water
In order to protect our health, all drinking water must be cleared of pathogens and impurities before it is used.
Waste Water
To ensure the water does no harm to people or the environment when it is released, waste water must be treated to reduce the level of contaminants to acceptable levels.
Industrial Uses
For industry, coagulants provide a method of reusing water in a cost-effective way that does not comprise the industrial process.

FAQs

How do inorganic coagulants work?

Coagulants have a positive electrical charge. By contrast, particles which are dissolved or suspended in water typically have a negative charge. The positive charge of the inorganic coagulant neutralises the negative charge of the particle and the two bind together (coagulate) in larger particles in a process known as flocculation.

These larger particles (known as floc) are heavy and quickly settle to the bottom of the water in a process called sedimentation. Lighter flocs can be removed from the water using filters. Different coagulants target different types of particles in the water.

 

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