Effects of temperature, oxygen level, ionic strength, and pH on the reaction of benzene with hydroxyl radicals in aqueous atmospheric systems

In order to assess the degradation of aromatic compounds in fog, the reaction of benzene with hydroxyl radicals was studied in a bulk aqueous system. The effects of temperature, oxygen content, ionic strength, and pH were investigated in a batch reactor by following the two main products, phenol and biphenyl. The reaction rate increased with temperature, but was not significantly affected by ionic strength and pH. The overall phenol yield also did not significantly change with the removal of oxygen from the system. Conversely, the formation of biphenyl was more favorable under conditions of low oxygen content, high ionic strength, and low pH. The pH of the solution decreased during the reaction due to the formation of oxidation products of phenol; thus, we found that biphenyl did not form in detectable concentrations unless the pH was at or below 4.50–4.80.