Other Advanced Oxidation Methods

A process called direct chemical oxidation has been proposed for the destruction of solid and liquid organic wastes in the aqueous phase, particularly in environments such as those under buildings, where the light required for UV processes cannot conveniently be supplied. It uses one or another of the strongest known chemical oxidants—e.g., acidified peroxydisulfate anion, S2082-, under ambient pressure and moderate temperatures to oxidize the wastes. Such a process needs no catalysts and produces no secondary wastes of concern. The sulfate that results from the peroxydisulfate can be recycled back to the oxidant. Other very strong oxidizing agents that have been tested are the peroxymonosulfate anion, HS05~~, and the ferrate ion, Fe042~; in the latter, iron has an oxidation number of +6, so it is not surprising that it is a strong oxidizing agent. Unfortunately, ferrate ion suffers from the problem of instability.

PROBLEM 14-16

Deduce the balanced half-reaction (acidic media) in which the peroxydisulfate ion is converted into sulfate ion. Repeat the exercise for the conversion of oxalic acid, C^H^O^, into carbon dioxide. Combine these half-reactions into a balanced equation, and calculate the volume of 0.010 M peroxydisufate that is required to oxidize one kilogram of oxalic acid.

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