Home > News > Content

  • CONTACT US

  • Sunresin Park, No.135, Jinye Road, Xi'an Hi- tech Industrial Development Zone, Shaanxi, 710076, China

  • TEL: +86-29-8918 2091

  • FAX: +86-29-8845 3538

  • Email: seplite@sunresin.com

Using Ion Exchange Properly Mar 03, 2015

Ion exchange resins are designed to decrease undesirable ions and ionic substances in water. Ion exchange technology has been around in the U.S. since the early 1900s and although ion exchange resin has commonly been used to soften water, research and development have allowed for the manufacturing of resins that can reduce a wide variety of contaminants. Ion exchange resins can reduce contaminants in drinking water, such as arsenic, tannins, nitrates, chromium, perchlorates, barium and radium.


Looking at arsenic

 

Arsenic is found in many minerals and is tasteless and odorless. Arsenic enters drinking water supplies through natural deposits in the Earth from agricultural and industrial practices. Arsenic, if consumed in drinking water above the maximum contaminant level (MCL) of 10 parts per billion (ppb), can cause skin damage, circulatory system problems and an increased risk of cancer. In the U.S., arsenic is found commonly in the Midwest and Southwest regions. Arsenic in groundwater exists in the trivalent (III) and/or pentavalent (V) form.

A strong base anion ion exchange resin can be used to reduce arsenic in the water. Arsenic III must first be converted to arsenic V by oxidation. This can be done by using chlorine, peroxide, potassium permanganate or by a manganese greensand filter. Ion exchange resin does not like oxidizing agents and continued exposure can lead to a decrease in the resin''s performance.

Therefore, low doses of the oxidizing agent should be used and the oxidizing agent should be removed before feeding the water to the resin. Pre-oxidation instructions can be provided by your ion exchange resin manufacturer. If using a manganese greensand filter, some of the arsenic will be removed in the process. The strong base anion resin is regenerable with salt and can be reused over and over. Strong base anion resins can also be used to remove tannins in drinking water.

 

Knowing tannins and nitrates


Tannins are natural organic materials that are byproducts of the fermentation process. Tannins give water a light yellow color and often create stains on tubs, toilets and sinks and sometimes are mistaken for iron staining. Tannins can give water a tangy aftertaste. Tannins are considered to be an aesthetic problem and can be removed by a strong base anion ion exchange resin that has been specifically designed for that purpose.

These strong base anion resins are also often referred to as organic scavengers. These resins are easily regenerated with salt, and either sodium chloride or potassium chloride can be used. The typical salt dose is 8-10 pounds per cubic foot of resin. Any time the water hardness is 10 grains per gallon or higher, the water must be softened prior to coming into contact with the organic scavenging resin. Strong base anion resin or weak base anion resin can also be used to remove nitrates in the drinking water.

Nitrates occur naturally on Earth in large deposits and to get into drinking water by runoffs from fertilizer use, sewage and erosion of natural deposits. The MCL for nitrates in drinking water is 10 parts per million. Infants who drink water with nitrates above the MCL can become extremely ill. Areas in the U.S. with shallow groundwater and less extensive woodlands are at a higher risk for nitrate contamination.

Nitrates can be removed through ion exchange by using a strong base anion or a weak base anion resin. This can be done inexpensively and on a whole-house basis. Standard anion resins prefer sulfates over nitrates, and therefore are subject to nitrate dumping. However, most ion exchange resin manufacturers supply nitrate selective resins that will not dump nitrates. When using a nitrate selective resin, the hardness level cannot exceed 10 grains per gallon, and the iron content must be less than 1 parts per million (ppm).


Resins effective against other contaminants


Chromium is a metal that is odorless and tasteless. Chromium enters water through erosion of natural deposits and discharge from industrial mills. The MCL for total chromium is 100 ppb and includes all forms of chromium, including chromium-6. Chromium-6 causes adverse skin reactions and some research considers chromium-6 to be a carcinogen. Weak base anion resins can be used to remove ppm levels of chromium-6 in groundwater. The weak base anion resins that are specified for chromium removal work best when the pH is 6 or less.

 

Perchlorates occur naturally in the environment and as a man-made chemical that is used to produce rocket fuel, fireworks, flares and explosives. Perchlorates can also be in bleach and some fertilizers. Perchlorates have been found in approximately 46 states in the U.S. and can cause adverse effects on the thyroid gland. Strong base anion resins will remove perchlorates and some can reduce the perchlorate levels to less than 1 ppm. These resins are not recommended for regeneration. They are meant to be used and then disposed of properly.

 

Barium is a metal which exists in nature in ores containing mixtures of elements. Barium also finds its way into the environment from discharge of metal refineries, drilling wastes and erosion of natural deposits. The MCL is 2 ppm. People who drink water containing barium exceeding the MCL can experience an increase in blood pressure.

 

Radium is a metal that exists commonly as radium-226 and radium-228. Radium can be found in low levels in water, soil, rocks, plants and animals. The MCL of radium is 5 picocuries per liter and long-term exposure can lead to an increased risk of cancer. Both radium and barium can be removed by strong acid cations. The strong acid cations are supplied in the sodium form. Barium will be removed up to the capacity of the strong acid cation resin for the total hardness removal. Radium-226 and -228 can be removed by strong acid cation resin beyond its capacity for total hardness removal. Therefore, it is best to limit the service cycle to the capacity of the resin for removal of hardness. Sodium chloride or potassium chloride can be used to regenerate the resin.

 

Whether the contaminants present in the drinking water include arsenic, tannins, nitrates, chromium, perchlorates, barium, radium or any other undesirable material, ion exchange resin may be the solution. The first step is to collect a sample of the water to be treated and have a complete analysis performed. The water analysis results can be reviewed by your ion exchange representative to determine which resin is best suited to reduce the contaminant and the operating parameters of the resin. Multi-contaminant removal can also be achieved by ion exchange.