High Energy Electron Beam Radiation Process For The Removal Of Benzene And Toluene From Aqueous Solution

INTRODUCTION

Aromatic hydrocarbons have been introduced to the environment
from a variety of sources. Many of these compounds are resistant
to degradation and pose a potential health threat to human
populations. Concern about the potential hazards of these
compoundshas resulted in government policies that require the
remediation of contaminated soil, sediments, and the treatment of
surface and ground waters, and wastewater.. On March 6, 1990
benzene was added to the Resource Conservation and Recovery Act
(RCRA) list of hazardous compounds by the Environmental
Protection Agency (EPA). The level mandated in solid
waste or wastewater is 0.5mg L (Hanson, 1990). Benzene is
also regulated under the 1986 Safe Drinking Water Act amendments
(SDWA) at a maximum contaminant. level' (MCL) of 0. mg L with
a maximum contaminant level' goal (MCLG) of 0 mgL because of
its known carcinogenicity (Fed. Reg., Jul 1987, Pontius, 1992).
Under the same SWDA amendments, toluene must be by all
drinking water systems and is not to exceed 1 mg L (Fed. Req.,
Jan 1991, Pontius,. 1992). Therefore, the destruction of benzene
and toluene in these wastes necessitates the development of
treatment technologies capable of degrading these compounds from
a variety of matrices.

One potentially efficient method of destroying aromatic
hydrocarbons is through chemical oxidation by hydroxyiradicals
(0H). These can beeffectively generated by high energy
electron beam radiation. Earlier work reported the destruction
of benzene and alkyl—substituted benzenes from a variety of
aqueous matrices (Nickelsen, et al., 1992). However, in all
cases, 0H scavengers, e.g. 3.3 mM methanol, were present, and
therefore factored into the estimates of hydrocarbon removal
efficiencies. In addition, no reaction by—product analyses were
included in previous studies.

In this study we have evaluated the removal of benzene and
toluene from aqueous solution as a function of absorbed dose, pH,
and total solids content. Through the identification of dose
dependent intermediate and final reaction by—products, we have
confirmed a reaction mechanism resulting mainly from OH attack.