Fraunhofer Institute for Ceramic Technologies and Systems IKTS and inopor GmbH jointly won the 2015 ACerS Corporate Environmental Achievement Award for their development of ceramic nanofiltration membranes for efficient water treatment.
Membrane filtration is an important cleaning process in water treatment. Depending on the pore size of the membrane, a removal of particles, microorganisms (bacteria, viruses), dissolved organic components as well as salts is possible. Nanofiltration is a specific membrane filtration range with a very low pore size smaller than 2 nm to reject organic molecules with a molar weight below 1,000 Da (1 Da = 1 g/mol) and to remove multivalent salts (carbonate, sulphates).
15 years membrane development and membrane business
The worldwide first ceramic nanofiltration membrane with a molecular weight cut-off (MWCO) of 450 Da was jointly developed by Fraunhofer IKTS and Rauschert already between 1997-2000. These membranes were intensively tested for the cleaning and recycling of hot wastewater of textile companies close to the washing machine. Based on the semi-technical manufacturing capabilities of IKTS, a first plant containing 25 m2 was equipped in 2002. After four years of continuous operation of this first plant there was a confidence in the membrane stability and inopor GmbH was founded as a subsidiary of Rauschert to enlarge the membrane production to full technical scale.
Many different applications have been realized in wastewater cleaning, water treatment, product recovery, potable water production, biomass treatment as well as catalyst recovery. A few applications came up where the cut-off of the membrane was not sufficient or the flux of the membrane dropped down quickly because of pore blocking. This was the reason for developing a second generation of ceramic nanofiltration membranes by the partners between 2000-2013 with a reduced MWCO of 200 Da. This new membrane is just now introduced in the production of inopor GmbH.
The membrane thickness of inoporÒ nanofiltration membranes is only 50 nm. The basis of the defect-free preparation of these membranes in a scale of thousands square meters is a high quality substrate and a unique mastery of the sol-gel technique. The final membrane consists of titania and zirconia with a pore size of smaller than 1 nm and a high microporosity of about 30 %. The water flux of the inoporÒ nanofiltration membranes in application is 100-200 l/(m2h) (ten times higher compared to polymer membranes) with a high salt retention of > 80 % of multivalent salts. Despite the small pores and high microporosity, the membranes have a high stability in acidic (7 wt% HCl, 25 °C) and alkaline solutions (16 wt% NaOH, 60 °C).
There are many successful applications of inoporÒ nanofiltration membranes, such as:
- Production integrated cleaning of waste water (treatment of partial waste water streams with recycling of the water)
- Cleaning and reuse of coolants and lubricants
- Cleaning and reuse of washing and cleaning baths (e.g. bottle cleaning)
- Separation of products in chemical and pharmaceutical industries
- Product cleaning and washing by diafiltration
- One-step production of portable water from surface and ground water
(disinfection, removal of organics, partial desalination)
- Efficient treatment and cleaning of “produced water” from oil & gas
inoporÒ nanofiltration membranes consist of inorganic, environmental friendly materials (Al2O3, ZrO2, TiO2). The robustness of the inorganic material results in a long-term stability of the membranes (> 10 years) and a low maintenance. With inoporÒ nanofiltration membranes a water treatment without chemicals is possible with high water savings (recycling of up to 90-95 %) as well as energy savings (recycling of hot water). An additional impact is achieved by cleaning in place and recycling of washing and cleaning baths (increase of lifetime by factor 3-5).
About Fraunhofer IKTS
The Fraunhofer Institute for Ceramic Technologies and Systems IKTS covers the field of advanced ceramics from basic preliminary research through to the entire range of applications. Superbly equipped laboratories and technical facilities covering 30,000 m2 of useable space have been set up for this purpose at the sites in Dresden and Hermsdorf. The development of ceramic membranes for liquid filtration as well as gas separation including membrane process engineering belong to the core competencies of IKTS. The group with 60 people is one of the biggest one worldwide.
About inopor GmbH
inopor GmbH is a 100% subsidiary of the company Rauschert. Rauschert is a family-owned, German technology company with over 110 years of experience in manufacturing advanced technical ceramics. The company employs 1200 employees in 12 plants and 6 sales offices in 12 countries. In 2009, Rauschert diversified successfully into renewable energy generation and decentralized energy systems with a clear focus on industrial customers.