Cleaning Waste Water Effectively
In industry, water is a must: in many production processes, it serves as a solvent, detergent, to cool or to transfer heat. As more and more water is consumed, waste water has to be treated and reused. Ceramic membranes offer a good way to do this: since they are separated mechanically – similar to a coffee filter – they are particularly energy-efficient. However, this method previously came to an end when a molecular size of 450 Da was reached: smaller molecules could not be separated with ceramic membranes. According to experts, it was even considered impossible to go below this limit.
Dr Ingolf Voigt, Dr-Ing. Hannes Richter and Dipl.-Chem. Petra Puhlfuerss from the Fraunhofer IKTS have achieved the impossible. “With our ceramic membranes, we achieve, for the first time, a molecular separation limit of 200 Da – and, thereby, a whole new quality,” says Dr Voigt, Deputy Institute Director of the IKTS and Site Manager in Hermsdorf. It was first necessary to overcome various obstacles. The first was in the production of the membrane itself: if such small molecules were to be separated reliably, a membrane was needed that had pores smaller than the molecules which were to be separated. In addition, all of the pores had to be as similar in size as possible, since a single larger opening is sufficient to allow molecules to slip through. The challenge was therefore to produce pores which were as small as possible, with all of them having more or less the same size. The results were achieved by refining the sol-gel technology. The second hurdle was to make such membrane layers defect-free over larger surfaces. Whereas only a few square centimetres of surface are usually coated, the Fraunhofer researchers equipped a pilot system with a membrane area of 234 m2, which means that their membrane is several magnitudes larger. Commissioned by Shell, the pilot system was built by the company Andreas Junghans – Anlagenbau und Edelstahlbearbeitung GmbH & Co. KG/DE and is located in Alberta/CA. The system has been successfully purifying waste water since 2016, which is used for the extraction of oil from oil sand. The researchers are currently planning an initial production facility with a membrane area of more than 5000 m2. The innovative ceramic membranes also offer advantages in industrial production processes: they can be used to purify partial currents directly in the process as well as to guide the cleaned water in the cycle, which saves water and energy. For the development of the ceramic nanofiltration membrane, Dr Ingolf Voigt, Dr-Ing. Hannes Richter and Dipl.-Chem. Petra Puhlfuerss have received this year’s Joseph-von-Fraunhofer Award. The jury justifies the award by mentioning, among other things “the first-ever implementation for filtration applications within this material class.”