Recycling process water is a growing need for a variety of industries faced with increasing water costs and environmental constraints. Metal finishing activities such as printed circuit board (PCB) manufacturing generate large volumes of rinse water slightly contaminated with inorganic chemicals and organic additives. While the former can be removed with proven technologies, there is a need for effective processes for elimination of trace organics in order to allow recycling of rinse water without negative impact on process bath quality.
A cooperative research project started recently to study a water recycling process adapted to this need, able to remove 95% of the Chemical Oxygen Demand (COD) of the rinse water by combining proven membrane separation with an innovative chemical oxidation. Two types of advanced oxidations based on the conjunction of heterogeneous catalysts with oxidants will be specifically investigated.
In a preliminary stage of the project, the experimental tests were performed with a set of model compounds, selected from among the chemicals most frequently used in the plating processes, namely chelating agents, surfactants and corrosion inhibitors. These compounds were oxidized comparatively by ozone and catalytic ozonation. The differences between standard oxidation and catalytic oxidation are presented and discussed.