Insight into sub-critical wet oxidation of phenol

Abstract

Low molecular weight organic acids, especially acetic acid, are often formed during wet oxidation. The role of mass transfer in the formation of acetic acid in wet oxidation was studied. For this purpose, phenol was considered as a model substrate. Acetic acid formed was maximum when mass transfer limitations existed. The waste may contain free radical initiators or scavengers. Therefore, the model compound hydroquinone was used as a free radical generator. It accelerated degradation but acetic acid formation increased. On the other hand, t-butanol as a free radical scavenger suppressed both phenol degradation and acetic acid formation. The strongly alkaline pH resulted in more acetic acid formation, though rates of phenol degradation increased. Wet oxidation of phenol was also studied in the presence of the homogeneous catalysts cupric sulfate and ferrous sulfate. The effects of these catalysts on the rates of oxidation and the acetic acid formation were studied. The amount of acetic acid formed in the presence of ferrous sulfate was relatively higher.