Zeolite-assisted radiolysis of aromatic chlorides mitigating influence of coexisting ions in water matrix

Abstract

We have studied zeolite-assisted radiolytic degradation of aromatic chlorides in the presence of radical scavengers. This study aims to determine whether the combined use of zeolite with ionizing radiation can reduce the influence of water matrix in the irradiation treatment of water-soluble organic compounds. A high-silica mordenite-type zeolite (HMOR) was used as the adsorbent for the aromatic chlorides. We investigated and compared the effects of HMOR on the radiation-induced degradation of three aromatic chlorides, 2-chlorophenol (2-ClPh), 2-chloroaniline (2-ClAn), and 2-chlorobenzoic acid (2-ClBA). The irradiation experiments were performed by using a Co-60 γ-ray source and bromide, nitrate and formate ions were used as the radical scavengers. In the presence of these radical scavengers, the degradation of 2-ClPh in water was inhibited, but the combined use of HMOR much improved the degradation yield. This improvement was attributed to high performance of HMOR in adsorption of 2-ClPh. Similarly, HMOR was effective for adsorption of 2-ClAn from water and facilitated the 2-ClAn degradation in the presence of formate ion. In contrast, HMOR was poor at adsorption of 2-ClBA and consistently the radiation-induced degradation of 2-ClBA in the water-HMOR mixture was inhibited by formate ion. These results demonstrate that HMOR can mitigate the influence of radical scavengers in water and facilitate the radiation-induced degradation of a molecule such as 2-ClPh and 2-ClAn, providing HMOR strongly adsorbs that molecule.