Purification of wet-process phosphoric acid

I'm doing my senior design class and I have design a chemical plant that produces phosphoric acid by reacting phosphate rock with sulfuric acid. The phosphate rock has a lot of impurities, some of which I know how to separate but there are some impurities that I'm completely lost about. The impurities are: $\text{Al}_2\text{O}_3$, $\text{Fe}_2\text{O}_3$, $\text{MgO}$, $\text{Na}_2\text{O}$, $\text{K}_2\text{O}$. How would these react in a mixture of water, sulfuric acid and phosphoric acid and how would I purify them out of my crude phosphoric acid? Or at least, what's a reasonable assumption to make to make my plant design a little straightforward.

• What are the concentrations of the impurities, this is quite an important factor as it can mean certain reactions should be prioritized? It also would help to know to what purity you want the phosphoric acid at the end. – BOB Feb 11 '16 at 19:05