What is the easiest and/or most efficient method of reducing and converting ferric oxide to ferous sulfate?

Question

Fe2O3 = FeO4S ???

Answer 1

I hope this is a help to you, I could hardly find anything that you mentioned in your question (I did a Google search).
I found this and I hope that it is close to what you asked for, if not exactly what you asked for.

Iron forms two series of compounds, ferrous and ferric (more recently known as iron(II) and iron(III) compounds.) The most familiar of ferric materials is rust, a hydrated ferric oxide. Iron tonics and tablets may contain either ferrous compounds such as ferrous sulphate or ferric compounds, including ammonium ferric citrate.

It is possible to convert ferric compounds to ferrous compounds; this requires the addition of electrons to the metal, a process known chemically as 'reduction'. The chemical which loses the electrons to the iron is know as a reducing agent and is 'oxidised' in the process.

It is also possible to oxidise ferrous compounds to ferric, which is generally the more stable of the two states under most normal conditions on earth which has an atmosphere containing oxygen. The relative stability of the two forms also depends on the acidity (pH) of the solution and also the other materials that are attached to the iron atom.