The influence of radical transfer and scavenger materials in various concentrations on the gamma radiolysis of phenol

The influence of a radical scavenger (tert-butanol (t-BuOH)) and two radical transfer materials (formic acid (HCOOH) and formate anion (HCOO−)) on the radical set during radiolysis of a simple model compound, phenol (PhOH, 1.0×10−4 mol L−1) is discussed in this study. PhOH solutions were irradiated with γ-rays, in the presence of 1.0×10−3, 5.0×10−2 and 5.0×10−1 mol L−1t-BuOH, HCOOH or HCOONa under deoxygenated and O2-saturated reaction conditions. The rate of transformation of PhOH increased significantly in the presence of dissolved O2. The radical transfer or scavenger materials used reduced the rates of transformation of PhOH in O2-saturated solutions to a similar degree. The simultaneous presence of O2 and the organic additives in excess proportionally to PhOH results in the conversion of the radical set to less reactive intermediates (t-
- OOBuOH, HO2
- or O2
- -), which made minor contribution to the transformation of PhOH. Under oxygenated conditions, t-BuOH and HCOOH in low concentrations slightly promoted the degradation, as opposed to HCOO− which reduced it. However, using higher additive concentrations, their competitive reactions for the primary intermediates came into prominence, thus they reduced the efficiency of PhOH decomposition. HO2
- and O2
- -, and also the carbon-centred radicals formed (order of their reactivity t-
- BuOH>
- COOH>CO2
- -) have only a minor contribution to the degradation of PhOH, and the reactions of
- OH+PhOH and eaq−+PhOH are the significant processes.