Is it possible to go back from magnesium sulfate ($\ce{MgSO4}$) to magnesium oxide ($\ce{MgO}$) and sulfuric acid ($\ce{H2SO4}$) ?

How difficult or easy would it be?

The reason I ask is because epsom salts ($\ce{MgSO4}$) are really cheap (i.e. less than 50 euro cents / kg). Whereas magnesia ($\ce{MgO}$) of $98\%$ or better grade is much more expensive (i.e 3-4 euro / kg).

I was wondering how easy and cheap it would be to revert the reaction and separate out the sulfur from the magnesium oxide.


1 Answer 1


Yes, magnesium sulfate can be converted back to magnesium oxide by thermal decomposition or use of reducing agents.

  1. Thermal decomposition

$$\ce{2MgSO4 ->[\Delta] 2MgO + 2SO2 ^ + O2 ^}$$

The thermal decomposition of magnesium sulfate to produce magnesium oxide, sulfur dioxide and oxygen. This reaction takes place by heating to the temperature of 1137°C.(Chemiday 1)

  1. Use of reducing agent

$$\ce{2MgSO4 + C ->[\Delta] 2MgO + 2SO2 ^ + CO2 ^}$$

Magnesium sulfate react with carbon (as reducing agent) to produce magnesium oxide, sulfur dioxide and carbon dioxide. This reaction takes place at a temperature of 700-900°C. (Chemiday 2)

The products other than magnesium oxide are gaseous and escapes leaving behind pure magnesium oxide.

  • $\begingroup$ Thanks for your answer. In example 2, is it sufficient for me to add as a Carbon source the fuel I use to burn the Magnesium Sulfate? Say for example I use a propane fire to burn the Magnesium Sulfate, is the added Carbon from the propane enough? Or for that matter any other hydro-carbon fuel? $\endgroup$
    – made2hack
    Feb 5, 2017 at 8:14
  • $\begingroup$ You have to use pure carbon $\endgroup$ Feb 5, 2017 at 13:53

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