Ion exchange chromatography experiment involving transitional metals

[Horseb0x]

I did an experiment in which I used an anion exchange resin to separate nickel from cobalt but I don't understand the theory behind it. What I know is that the ion exchange resin uses quaternary ammonium groups as its cations but that's about it.

First we packed a column with the resin then ran NaCl solution through it in order to attach chloride anions to it. Next we ran conc. HCl through it to "condition" the resin. Thats all the lab manual said about it. What does this mean? What does the 9M HCl solution do when I ran it through the column? Next we added an unknown mixture of Ni2+ and Co2+ ions and ran more conc. HCl through the column to elute the Ni2+. I know that Co2+ reacts with conc. HCl to form a chloride complex while Ni2+ does not but why does conc. HCl cause the nickel to elute but leaves the cobalt complex behind? Does the cobalt complex act as an anion itself and bond to the cations on the exchange resin or something?

 

[jbsteele]

The theory behind anion exchange chromatography using a quaternary ammonium resin is that the cationic groups on the resin interact with anions in solution to form ionic bonds. The chloride ions from the NaCl solution form bonds with the cationic groups, creating a positively charged surface on the resin. When you ran the 9M HCl solution through the column, it removed the chloride ions from the resin and replaced them with protons (H+). This created a negatively charged surface on the resin which allowed for the Ni2+ and Co2+ ions to interact with the cationic groups. Since the Co2+ ion forms a strong complex with chloride, it was unable to interact with the cationic groups and remain adsorbed to the resin. The Ni2+ ion, however, does not form a strong complex with chloride and was therefore able to interact with the cationic groups and be eluted from the column.