How Reverse Osmosis Works
Although membrane separation processes have been known since the 1930s, membranes became more practical after Leob and Sourrajan developed the "skinned" reverse osmosis (RO) membrane in 1959.
What Is Osmotic Pressure?
Before examining reverse osmosis, it is necessary to understand osmotic pressure. Osmosis is the process by which water moves from a less concentrated solution (a hypotonic solution) through a semipermeable membrane (such as a cell membrane) into a more concentrated solution.
Rice soaked in water swells after a while. In fact, it swells—or expands—as water moves from a less concentrated environment (the aqueous solution) to a more concentrated environment (the rice). However, the solid molecules inside the rice cannot pass through the cell membrane into the aqueous solution. This creates pressure on the cell membrane, which is called osmotic pressure. Due to osmotic pressure, the membrane expands toward the aqueous solution.
Another example can be drawn from the plant kingdom. Thanks to osmotic pressure, plants also absorb the water and nutrients they need from the soil through their roots.
What Is the Working Principle of Reverse Osmosis?
Water tends to move from a less concentrated solution to a more concentrated one. The process by which water is forced (using a driving force, such as pressure) through a membrane from a more concentrated solution to a less concentrated one is called reverse osmosis. The system composed of the materials necessary to carry out this process is called a reverse osmosis system.
Why Is Antiscalant Used?
In membrane systems, the water passing through the membrane emerges with a high degree of purity, while a high concentration of impurities remains on the membrane. When these impurities reach a certain concentration, they form crystals that build up, impairing the membrane’s ability to allow water to pass through and eventually causing the system to clog.
For this reason, the use of antiscalants is necessary in membrane systems.
When added to the feedwater of a membrane process, antiscalant delays the precipitation/crystallization points of salts present in the water (CaCO₃, CaSO₄, SiO₂, BaSO₄, MgSO₄, CaF₂, etc.) and reduces fouling through its high capacity to dissolve scale and contaminants. This extends the service life of the membranes.
When the selected antiscalant is applied correctly, it significantly delays crystallization, thereby causing blockages to occur much later. The need for sulfuric acid and hydrochloric acid decreases, and the risks associated with the use of these chemicals are reduced. Operating costs, as well as cleaning and maintenance costs, are reduced. It enables a higher recovery rate in reverse osmosis systems, allows the system to operate for longer periods, reduces the concentrate flow rate, and extends membrane life.
Membranes that are clogged or have developed bacterial growth can be cleaned with membrane-cleaning chemicals and restored to a usable condition.
At Cemkimsan Kimya, we have developed and manufacture at our plant our antiscalant products;
C-SCALANT 6080: A protective product for membranes fed with water containing high levels of silica. It prevents membrane fouling and extends their useful service life.
C-SCALANT 2005: A membrane protection product. It prevents membrane clogging or a decrease in capacity and extends their useful service life.
C-SCALANT 1085: A membrane protection product. It prevents membrane clogging or capacity loss and extends the useful service life of the membranes. Suitable for use in drinking water production facilities. NSF-certified.
Cleaning clogged and bacteria-infested membranes;
C-MEC 102: Acidic membrane cleaner; used to clean membranes whose pure water production capacity has decreased due to scale and similar contaminants. It is an acidic product with a low pH value.
C-MEC 100: An organic acidic membrane cleaner used to clean membranes whose pure water production capacity has decreased due to scale and similar contaminants. It is an acidic product with a low pH value.
C-MEC 200: Basic membrane cleaner; used to clean membranes whose pure water production capacity has decreased due to colloidal and similar contaminants. It is a basic product with a high pH value.
C-MEC 17: Membrane Disinfectant is a membrane cleaning chemical used to remove biological deposits that accumulate on R.O. membranes over time.
Source:
https://www.cemkimsan.com.tr/post/antiskalant-ve-membran-temizleyiciler
https://evrimagaci.org/ozmoz-ozmotik-basinc-ve-turgor-basinci-4519#
http://www.suvecevre.com/edergi/19/149/index.html
TMMOB Chamber of Chemical Engineers; Water Handbook
Cemkimsan Chemistry Lecture Notes