Talk:Cation-exchange capacity

Draft rewrite

A draft for a rewritten article is open for comment: User:Kyle MoJo/CEC draft Any input would be welcome! Kyle MoJo (talk) 15:50, 25 June 2017 (UTC)

The rewritten article has now been put up as the mainspace article Kyle MoJo (talk) 06:33, 6 July 2017 (UTC)

Rewrite proposal

I'm working up to a significant rewrite of this article, which seems justified. Here is a draft structure. Any objections, comments or suggestions?

• Lead
• Definition and principles
  • definitions and units of measurement
  • surface charges and colloids
  • clay minerals
  • organic matter
• pH and CEC
• Measurement
  • measurement approaches
  • potential CEC vs effective CEC
• Typical values (merging of existing sections Various colloids and soils' CEC and Standard values)
• Base saturation
• Applications
• Anion exchange capacity

The existing section Aluminium ions and CEC would be deleted - it is completely without citations.

Also, in agreement with Jlhollin, relevance is not limited to agriculture. I propose moving the farming portal to the bottom of the page.

Kyle MoJo (talk) 19:56, 10 March 2017 (UTC)

2016

Plus, measurement of cation exchange capacity is not limited to agronomy and soil science. It is used in oil and gas and possibly other fields where clay or clay minerals are important. This page should reflect that agronomy is an important user, but not the only one.

Unfortunately I'm not knowledgeable enough to rewrite the page. More on the oil industry use of this is at http://www.glossary.oilfield.slb.com/en/Terms/c/cation-exchange_capacity.aspx Jlhollin (talk) 22:35, 10 February 2016 (UTC)

2009

{{Editsemiprotected}} This page is poorly written and badly needs updating by an expert. CEC is a fundamental aspect of soil science and should be regarded as higher than "low" priority. As evidence of its poor writing, I consider the following:

"In soil science, cation exchange capacity (CEC) is the capacity of a soil for ion exchange of Cations between the soil and the soil solution. CEC is used as a measure of fertility, nutrient retention capacity, and the capacity to protect groundwater from cation contamination. Cations can also be easier to understand by just adding the group number."

The italics show a sentence which does not make sense in the context of the preceding sentences and no information about which "group number" is given. This sentence should be moved and clarified or omitted.

Also...

"The quantity of positively charged ions (cations) that a clay mineral or similar material can accommodate on its negatively charged surface is expressed as milli-ion equivalent per 100 g, or more commonly as milliequivalent (meq) per 100 g. Clays are luminosity in which some of the aluminium and silicon ions have been replaced by elements with different valence, or charge."

The bolded text makes no sense whatever. Also the whole section on Clay soils should be under a subheading since clay is only one type of soil and CEC is used for all types of soils.

"For example, aluminium (Al3+) may be replaced by iron (Fe2+) or magnesium (Mg2+), leading to a net negative charge. This charge attracts cations when the clay is immersed in an electrolyte such as salty water and causes an electrical double layer. The cation-exchange capacity is often expressed in terms of its contribution per unit pore volume, Qv."

There is no organization to these comments. It's as if they have been picked at random from a textbook. A better description if necessary.

Unfortunately, I cannot be of much more help as to what the pages should be changed to. I discovered this poorly written page when I was attempting to look up CEC for my own education.

Timothykinney 05:56, 4 May 2009 (UTC)

Hi. Would the addition of the word base make this sentence more precise? "Thus, a site with high base cation exchange capacity takes longer time to acidify (as well as to recover from an acidified status) than a site with a low cation exchange capacity (assuming similar base saturations)."

Seems that way to me but I hesitate to edit the article as I'm a student of soil science and not a teacher. Many thanks. —Preceding unsigned comment added by 82.69.13.6 (talk) 20:43, 26 March 2009 (UTC)

Not done: please be more specific about what needs to be changed. fahadsadah (talk,contribs) 12:31, 4 May 2009 (UTC)

Introduction to Environmental Chemistry by Stanley Manahan contains a full description. This is the core text for 'Introduction to Environmental Pollution', a course at the University of Sussex. It is a well respected text, and the third edition is recent and authoritative. I will leave the actual edits to a more experienced contributor than myself. I hope this helps improve the article!

139.184.30.132 (talk) 12:24, 10 March 2010 (UTC)

2005

I saw that a previous entry had been deleted, but no explanation why. So I try and see if I have better luck ;o) . Saittam 11:30 Oct 6 2005 (CET)

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