An atomic force microscope study of calcium carbonate adhesion to desalination process equipment

effect of anti-scale agent

Khalid Al-Anezi, Daniel J. Johnson, Nidal Hilal

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

Whilst carbon dioxide is water soluble the system is somewhat complex and results in the presence of carbonate anions which interact with cations such as Ca2+ and Mg2+ present in seawater to form insoluble carbonates, especially at high temperatures. In multistage flash (MSF) desalination plants CO2 gas becomes less soluble in the brine as a result of the brines high temperature and high salinity which causes the pH to be in the range of 8-9. The presence of these conditions causes the release of CO2, simultaneous to the formation of scale deposits since its solubility is a function of the solution pH. The formation of scale deposits, such as CaCO3 causes fouling in the MSF distillers which has previously been studied by many researchers. A great amount of work has been carried out and more is yet to come in order to fully understand the role of various components and their interaction including the effectiveness of scale control techniques. The deposits may serve as an adsorbing film raising the speed of the loss of crystals or promoting the formation of scale deposits and therefore further adhesion on the wall surfaces of the MSF distillers and other process plant equipment leading to deterioration in the performance and efficiency of the whole desalination plant. This paper shows direct quantification of the adhesion forces between CaCO3 crystals and different process equipment surfaces under different conditions. This was carried out using an atomic force microscope (AFM) with an attached CaCO3 crystal as a colloid probe to bring the CaCO3 directly into and out of contact with the surfaces and measuring the resultant adhesion. This involved using surfaces different grades of roughness and carrying out measurements in synthetic sea water solutions of differing ionic strengths as well as with real seawater samples. Furthermore, the effect on measured adhesion of adding anti-scalant to the solutions was examined.

Original languageEnglish
Pages (from-to)359-370
Number of pages12
JournalDesalination
Volume220
Issue number1-3
DOIs
Publication statusPublished - 1 Mar 2008
Externally publishedYes

Fingerprint

Calcium Carbonate
Calcium carbonate
Desalination
adhesion
calcium carbonate
desalination
Microscopes
Adhesion
Deposits
Carbonates
crystal
seawater
Seawater
Crystals
carbonate
Brines
Gas plants
Water
Colloids
colloid

Keywords

  • Atomic force microscopy
  • Carbon dioxide
  • Colloid probe
  • Desalination
  • Scaling

ASJC Scopus subject areas

  • Filtration and Separation

Cite this

An atomic force microscope study of calcium carbonate adhesion to desalination process equipment : effect of anti-scale agent. / Al-Anezi, Khalid; Johnson, Daniel J.; Hilal, Nidal.

In: Desalination, Vol. 220, No. 1-3, 01.03.2008, p. 359-370.

Research output: Contribution to journalArticle

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