Due to a recent ban on carcinogenic Cr(VI) compounds by European legislation, industrial chrome plating processes are now being switched to Cr(III)-based alternatives. Chromium is electrochemically deposited from an electrolyte solution on injection-molded car parts, such as trim strips and control elements, and the parts are then washed in rinse baths. This not only results in valuable chemicals being lost from the process, but also creates heavily contaminated wastewater that requires intensive purification. The Cr(III) complexes contained in the wastewater, unlike the freely present Cr(VI) ions in previous rinse water, can only be precipitated and disposed of as metal sludge after very energy-intensive pretreatment.

This work investigated the possibility of an alternative wastewater treatment process. The new process, based on reverse osmosis, should enable both lower-energy treatment and recover chemicals and water for the chrome plating process.

Although many publications have demonstrated the high retention capacity of nanofiltration and reverse osmosis membranes for metal ions, their industrial application in electroplating has so far largely been lacking due to the favorable basic precipitation. Little is known in literature about the membrane-based concentration and recycling of electrolyte components in industrial processes. There are virtually no comparable publications, especially for the newly developed Cr(III)-based electrolytes.

This work has expanded the state of knowledge in many ways. Not only was the concentration of electrolyte components from simulated rinse water, the further purification and recycling of separated water and the energy efficiency of the process investigated, but also the experimental scale was increased at the same time in order to approach industrial application.

Only through the detailed analysis of two Cr(III) electrolytes and their wastewater the relevant plating components were identified. By revealing the complexity of these solutions, it became clear that a process that ensures the simultaneous recovery of all relevant components is preferable to other separation processes from an economic and practical point of view. Therefore, the investigations were designed for a newly developed reverse osmosis process without pretreatment.

The investigations in this study demonstrate for the first time the reusability of a reverse osmosis concentrate recovered from artificial Cr(III) rinse water in standardized chrome plating tests.

The remaining permeate, which contained residues of boric acid, could then be purified using a specially developed process in a second reverse osmosis treatment so that the water was of sufficient quality for reuse. The process mentioned makes use of the ionic interactions of sulfate and boric acid, which were previously only known to increase the solubility of both components. This work shows that, among other things, these interactions also increase the boric acid retention during reverse osmosis, which can be used for purification. Finally, this work was the first to use a hybrid high-pressure semi-batch/batch reverse osmosis process at up to 109 bar on a pilot scale. The investigations in this work not only showed its suitability for wastewater treatment through the recovery of the electrolyte components, but also through the drastic reduction in energy requirements (currently around 120 kWh/m³). Even including investigations that depicted the partially variable process conditions in industrial operations, energy savings of around 97% can be expected for the industrial process. With the help of the results and findings of the investigations that make up this thesis, a reverse osmosis system was finally designed for the company BIA Kunststoff- und Galvanotechnik GmbH & Co. KG. This was then designed, manufactured and installed by the company Nijhuis Industries. Thus, this work not only expanded the state of knowledge in the field of galvanic wastewater treatment, but also enabled a bridge to industrial application.