A process for treating an aqueous acid solution containing at least one element selected from the group of elements consisting of As, Sb and Bi, said process comprising contacting the aqueous solution with an organic phase comprising an organophosphoric compound having the general formula (RO).sub.3 P = O wherein R represents an unsubstituted or substituted alkyl, aryl or aralkyl group, while maintaining a temperature of between 10.degree. and 60.degree. C and an organic phase/aqueous phase ratio of between 0.1 and 5, whereby the elements of said group and acid are extracted from the aqueous phase to the organic phase, and separating the resultant pregnant organic phase from the aqueous phase.