Sciencemadness Discussion Board

The 'P' Cycle and pH range on aqueous solutions

mach747 - 29-10-2004 at 15:41

Hi all,

I know I will probably be flamed for asking these two questions but I just want to get it out of my system !!! :o ...Be patient, its a little long and tedious ...

First question, the phosphate cycle : It is said that ' Sorption of phosphates and polyphosphates on surfaces is well known, particularly onto clay minerals, by chemical bonding of the anions to positively charged surfaces on the clays. In general, high phosphate adsorption by clays is favored by low pH levels.”

How on earth do the clays end up with positively charged surfaces and why is phosphate adsorption by clays favored by low pH levels?

Second question, limited pH range of aqueous solutions and its effect on hydrated metal ions ...

“In principle, all hydrated metal ions donate a larger number of protons than that corresponding to their charge, forming anionic oxy/hydroxo metal complexes. However, the limited pH range of aqueous solutions means that not all elements theoretically capable of existing as oxo or hydroxyoxo complexes will be found in nature" ...

What was actually meant when they say that not all theoretically probable forms are actually found “in nature”?

I apologize if this seems trival but my thinking cap doesnt seem to respond well to these questions ...


Hermes_Trismegistus - 29-10-2004 at 17:59

Originally posted by mach747
How on earth do the clays end up with positively charged surfaces

Like a glass rod with a silk scarf, friction is your culprit.

JohnWW - 30-10-2004 at 09:54

It has to do with the structures of the polymeric silicates and aluminosilicates in the clays.