UNITED CHEMICAL & ENVIRONMENT TECHNOLOGY CO., LTD


Main Office – VP Chính: 215 Nguyen Van Dau St, Ward 11, Binh Thanh, HCMC. Tel: (028) 3550 1200 – Fax: (028) 3550 1201

Branch – Chi Nhánh: 200/1/16 Binh Loi, Ward 13, Binh Thanh, HCMC. Skype: chemical.environment.tech

Contact (Zalo, WeChat): 0918.676.245 ky@uce.com.vn   (Zalo): 0937.626.245 sales@uce.com.vn

1. What is DI Mixed Bed Water Treatment System? And its applications

Please refer to the article “RO Water System”.

DI (De-Ionized Water) is also known as deionized water – water in which ions (negative, positive) have been removed by some separate or combined treatment method..

DI water is more qualitative than quantitative, so the quality level should be given in units of measurement such as MegaOhm or µS/cm.

It is also important to distinguish deionized water and pure water, which is deionized water that no longer contains any ions but still contains impurities that are not ionic, while pure water only has water molecules, in addition to water molecules, there are no other ions or compounds.

Currently, many people still think that water filtered from RO system or distillation equipment (1st, 2nd pass ) are DI water, but in fact, these systems have not completely removed ions, so they need to be combined with other treatment. For example the following combinations to get deionized water:

  • – RO membrane -> Mixed Resin.
  • – RO -> EDI.
  • – Activated Carbon -> Cation Resin -> Anion Resin -> Distillation.
  • – Activated Carbon -> Cation Resin -> Degassing CO2 -> Anion Resin -> Mixed Resin.

In this article, only mainly refer to the DI water treatment system based on ion exchange resins and other combinations

DI water quality can reach the highest level of 18.2 MegaOhm or conductivity of 0.055 µS/cm. However, in reality reaching more than 10 MegaOhm is already high

DI water quality can reach the highest level of 18.2 MegaOhm or conductivity of 0.055 µS/cm. However, in reality reaching more than 10 MegaOhm is already high

Checking quality of DI water can only be done with online sensors to ensure accuracy, but taking samples to test elsewhere will have a large error.

2. Applications of water DI

The water treatment by combining the use of Ion exchanger resin with other process to ensure quality is free of ions, other impurities and microorganisms.

  • Electronics and semiconductors.
  • Chemical liroduction and cosmetic.
  • Laboratory, new technology research.
  • Medicine, biotechnology.
  • Metal surface treatment before liainting, lilating.
  • For high liressure boiler.

3.Working principle of ion exchange resin of DI, Mixed Bed

Feed water containing positive ions (eg Ca2+, Na+…) and negative ions (eg SO42-, Cl…) is passed through the first tower containing H+ based cationic resin. Here, the cationic ions are caught in cationic resin tower by replacing H+ of resin, H+ will separated from resin goes into water.

3Resin-H + Ca2++ Na+ -> 2Resin-Ca + Resin-Na + 3H+

After cationic resin tower, negative ions in water will be continued through anionic resin tower where exchange with the OH of resin and are caught here

3Resin-OH + SO42- + Cl -> 2Resin-SO4 + Resin-Cl + 3OH

OH that has just released will immediately combines with the H+ from the earlier tower, become H2O

H+ + OH+ -> H2O

Independent Cationic and Anionic resin towers

Independent Cationic and Anionic resin towers

4. Regeneration principle of resin

Over time, both cationic and anionic resins will saturated, and the effectiveness will be decreased until no capacity of Ion exchanged. The regeneration will follow the original service cycle design and based on actual saturation in operation.

The saturated cationic resin will be regenerated with H from diluted HCl and the saturated anionic resin will be regenerated with OH from the diluted NaOH. When regenerated, all cationic ions, anionic ions, chemical, and water are discharged totally into the waste line.

2Resin-Ca + Resin-Na + 3HCl -> 3Resin-H + [Ca2+ + Na+ + 3Cl (to waste)]

2Resin-SO4 + Resin-Cl + 3NaOH -> 3Resin-OH + [SO42- + Cl + 3Na+ (to waste )]

Two discharge lines from 2 columns of resin tower need to be put into 1 tank to neutralize pH, a chemical treatment system for further treatment before discharging into the environment (please contact us for help about this regenerated wastewater treatment)

In fact, to bring higher efficiency and durability to equipment, a de-gases tower unit is required after the Cationic resin tower to remove dissolved gases including CO2, H2S

5. Post-treatment with Mixed Bed or EDI to reach Ultrapure water quality

Theoretically, all ions are removed after going through 2 resin towers, but in practice it is still not thorough, so a further treatment, called Post -treatment is required to polishing to achieve 10 – 18.2 MegaOhm for Ultrapure water

To visualize the whole, there are 3 processing parts, for example:

Pre-treatment Treatment Post-treatment
Sand filter, Active cabon… Cation – Degases – Anion Mixed bed or Polisher
RO filtration EDI

6.What are similar and different from DI and Mixed Bed water treatment systems?

Mentioning DI water system, most understanding that have 2 independent Cationic – Anionic towers. Its advantage is that it is very easy to regenerate when the two acid and baz have opposite properties, however, the highest level of deionization has not been achieved, but must be further treatment with mixed resin, called Mixed Bed.

What is Mixed Bed? Mixed Bed is often used after the Cation – Anion resin tower or after the RO membrane for the highest demineralization water quality, the disadvantage is that it is quite time consuming because it is necessary to separate the mixed resin before regeneration and mix it again after regeneration. This can be regenerated in tower ( called Mixed Bed) or take out external regeneration (called Polisher Tower).

The continuously regenerated EDI without chemical, will replace Mixed Bed in some cases or some industries, but at cost is quite high if high capacity installed

To achieve the same demineralization quality, one of the following combination can be a selection

  • RO 2 passes -> EDI.
  • RO 1, 2 passes -> Mixed Bed.
  • Cation -> Degas -> Anion -> Mixed Bed.

DI Mixed Bed water treatment system works as above principle, however, depending on the water source quality and capacity, treated quality to choose the appropriate demineralization system for the lowest investment and operating costs.

Water treatement system with

Water treatement system with Active carbon – Cation –Degas – Anion – Mixed Bed

Cation – Anion – Mixed Bed

Cation – Anion – Mixed Bed

Mixed Bed must separate and mix cationic and anionic resins before and after regeneration

Mixed Bed must separate and mix cationic and anionic resins before and after regeneration

Ultrapure water with RO membrane 2 passes + EDI unit + UV for electronic, pharmaceutical

Ultrapure water with RO membrane 2 passes + EDI unit + UV for electronic, pharmaceutical

Ultra pure water treatment for pharmaceutical production

Ultra pure water treatment for pharmaceutical production

Ultrapure water with R ofilter + polisher resin + UV for electronics

Ultrapure water with R ofilter + polisher resin + UV for electronics

”Active

Active carbon filter -> Cationic resin -> Anionic resin -> Mixed Bed
Manual operation, low investment cost but requires high experience to handle

7. Basic essential equipment for measuring and monitoring

– Online flow meter with totalizer

– Conductivity and Resistivity, pH, TOC for feed water and treated water, and periodically microbiology testing

– pH of wastewater.

8. Our ability to supply – UCE Co., Ltd

– Design and install DI Mixed Bed, RO, EDI water treatment system.

– Periodic inspection, system maintenance, transducer cleaning and calibration.

– Supply of consumables.

– Check resin, regenerate, clean RO membrane and resin.

Contact us for support