that it makes it possible to destroy a greater variety of contaminating organic compounds and or that it reduces the level of residual contaminant with a lower degree of irradiation the addition of an iron salt improves the performance the present invention is described in more detail with the help of the following examples which are intended only to illustrate the invention but to which the scope of the invention is not limited various tests were carried out on an aqueous phenol solution 100 u03bcm of phenol l which has a ph of 3 the solution was subjected to various doses of irradiation while varying the residence time under the electron beam and the nature of the catalyst and or the content of catalyst were was modified each sample was subsequently analyzed by hplc in order to determine the variation in concentration of the contaminant the tests denoted 1c and 2c are comparative tests in which the phenol solution does not comprise catalyst 1c or comprises a tio 2 catalyst 2c for the tests according to the invention 3 to 9 the phenol solution additionally comprises the catalyst according to the invention fig1 to 3 represent the change in the level of phenol in aqueous solution on the ordinate in u03bcm as a function of the irradiation dose gy on the abscissa fig1 relates to the catalyst free aqueous solution of comparative example 1c fig2 relates to the aqueous solution with catalyst fe iii salt and persulfate of ex 4 fig3 relates to the treatment of the aqueous solutions of examples 5 curve represented by squares 5a curve represented by diamonds and 5b curve represented by triangles the residual content of phenol p in u03bcm is shown on the ordinate and the irradiation dose in.