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

摘要

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 x 10(-4) mol L-1) is discussed in this study. PhOH solutions were irradiated with gamma-rays, in the presence of 1.0 x 10(-3), 5.0 x 10(-2) and 5.0 x 10(-1) mol L-1 t-BuOH, HCOOH or HCOONa under deoxygenated and O-2-saturated reaction conditions. The rate of transformation of PhOH increased significantly in the presence of dissolved O-2. The radical transfer or scavenger materials used reduced the rates of transformation of PhOH in O-2-saturated solutions to a similar degree. The simultaneous presence of O-2 and the organic additives in excess proportionally to PhOH results in the conversion of the radical set to less reactive intermediates (t-(OOBuOH)-O-center dot, HO2 center dot or O-2(center dot-)), 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 center dot and O-2(center dot-), and also the carbon-centred radicals formed (order of their reactivity t-(BuOH)-Bu-center dot >(COOH)-C-center dot > CO2 center dot-) have only a minor contribution to the degradation of PhOH, and the reactions of (OH)-O-center dot+PhOH and e(aq)(-) +PhOH are the significant processes. (C) 2015 Elsevier Ltd. All rights reserved.