The output from a sorption routine in PHREEQC shows that I have a certain number of moles of selenium species sorbed to Hfo_w. However the solution composition shows the same number of moles present after sorption as was initially specified in the input solution. Why is there no apparent decrease in disolved Se? Does PHREEQC consider sorbed species to be in solution?
Also, I'm confused about the specification of sites and surface area in the surface data block. After reading the FAQ's on the website I have the impression that the number of surface sites is either a number of moles of sites to which 1 kg of solution will be added (FAQ 60) or the number of moles of sites present on 1 mole of Fe (FAQ 61). Which is correct? If I specify the moles of a site present (and the mass of solid if sites are related to moles of solid) why is it necessary to specify surface area.
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