Metal recovery in surface treatment units by using the 3PE reactor

Pollution from heavy metals arises mainly from industrial activities and, in this respect, it may be controlled and consequently reduced. The recovery of metals from industrial wastes is important, not only from an ecological point of view (toxicity), but also for economical reasons (recycling). At the present time, a large number of techniques are available to satisfy the stringent low concentration standards for waste water (Crine 1993; Verma et al. 1993). But for most of these techniques, it is not possible to have an immediate and total recycling of the recovered metal. With the development of the volumic electrodes, also called the flow-through porous electrodes, the electrochemical technique could be applied for the recovery of usable metals from effluents or dilute solutions and depollution. These electrodes are made up of a good conductor which has a porous structure through which the solution flows to be treated. In order to avoid disadvantages, such as the potential drop in the liquid phase and the problem of sealing, a new type of reactor called the Pulsating Porous Percolated Electrode (3PE) has been developed. This reactor eliminates the problem of plugging the particle bed by moving the matrix conductor during a fraction of time of the functioning of the reactor. This is done by using pulsed columns, which are largely used in different processes in chemical engineering. In this manner, one could expect to obtain the advantages of both the fixed and fluidized bed.