Discuss how you would separate Fe+3 from Ca2+
I would think Fe2S3 would form with H2S and CaS is soluble. You might have to play around with the pH before addition of H2S to avoid the reduction of S^2- to free S which usually is in the form of colloidal S.
To separate Fe+3 ions from Ca2+ ions, you can utilize several methods based on the differences in their chemical properties. Here are a few techniques that can be employed:
1. pH Control: Adjusting the pH of the solution can help in selective precipitation, where one ion is precipitated while the other remains in the solution. In the case of Fe+3 and Ca2+, you can increase the pH of the solution to around 9-10 to precipitate Fe(OH)3. Ca2+ ions will remain dissolved.
2. Complex Formation: Fe+3 ions are known to form complex ions with various ligands. Adding a suitable ligand that complexes with Fe+3, such as thiocyanate (SCN-), will form a deep-red colored complex, Fe(SCN)3. Ca2+ ions do not form a strong complex with SCN-, and thus, they will not interfere. The Fe(SCN)3 complex can be separated based on its color or by precipitation.
3. Solvent Extraction: Solvent extraction exploits the differences in solubility of the metal ions in different solvents. Selecting an organic solvent that dissolves one of the metal ions while leaving the other behind allows for their separation. In this case, Fe+3 can be extracted into an organic solvent like methyl isobutyl ketone (MIBK) or tributyl phosphate (TBP), while Ca2+ ions will remain in the aqueous phase.
4. Ion Exchange: This method relies on the different affinities of metal ions for specific ion exchange resins. In ion exchange, the sample solution is passed through a column containing an ion exchange resin with a preference for one metal ion over the other. For example, a cation exchange resin with selectivity for Fe+3 can be used to retain the Fe+3 ions, while the Ca2+ ions pass through.
It's important to note that the separation technique chosen depends on the specific circumstances, concentration, and feasibility. Additional factors like temperature, presence of other ions, and cost may also influence the selection of the separation method. It is recommended to consult a laboratory handbook or an expert in analytical chemistry for specific guidance when performing such separation methods.