Weldon process

The Weldon process is a process developed in 1870 by Walter Weldon for recovering manganese dioxide for re-use in chlorine manufacture.

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After reacting hydrochloric acid with manganese dioxide (and related oxides), the waste manganese(II) chloride solution is treated with lime, steam and oxygen, producing calcium manganite (IV):

2MnCl₂ + 3Ca(OH)₂ + O₂ → CaO·2MnO₂ + 3H₂O + 2CaCl₂

The resulting calcium manganite can be reacted with HCl as in related processes:

CaO·2MnO₂ + 10HCl → CaCl₂ + 2MnCl₂ + 2Cl₂ + 5H₂O

The MnCl₂ can be recycled, while the CaCl₂ is a waste byproduct.