Study of a 'zero discharge' process applied to the treatment of wastewater containing heavy metals and radionuclides by coupling nano-filtration and a controlled electrical elution

This thesis aim is to study a process designed to remove nickel and cobalt cations present in low concentrations from the wastewater of a nuclear fuel reprocessing facility. The proposed process combines nano-filtration and a sorption step in which the adsorbent (carbon felts) is a conductive material that may be electrically regenerated. Each step of the process is studied separately and its association is evaluated. Nano-filtration step is studied by an approach integrating experiments to numerical simulation. A simple experiment-based method was developed to supply the simulation software database, improving its predictive capacities. Three commercial nano-filtration membranes were compared in terms of a continuous or batch recycling operation mode. This has allowed the most suited membrane for the process to be chosen. Permeate produced by nano-filtration was used to study the sorption step. After a physical characterization of the carbon felts, its application was studied in two different stages. The first was a closed batch operation mode which allowed characterization of the sorption kinetics and obtaining equilibrium isotherms. The second was a fixed bed operating mode in which adsorbent breakthrough curves were studied. The influence of the operating conditions and the composition of the wastewater in the output result were analyzed. The carbon felts regeneration was investigated by both acid and electric regeneration. A process scheme using acid regeneration was proposed. The electrical one still required further study. (author)