Résultats exploitables
Electrodeposition of metal ions from low concentration aqueous solutions using specially developed three-dimensional electrodes has previously been successfully developed and manufactured by C-Tech Innovation Ltd. This work builds on this experience to allow selective deposition of metals in the presence of a range of other metal ions to achieve essentially pure metal deposits. This is a useful method of recovering metals in a valuable form from dilute solution in a range of industries e.g. PCB, hydrometallurgy, metal finishing.
A pilot plant has been built which uses two 3 d cathode cells to alternately deposit metal and strip metal. This gives the flexibility to generate either a solid metal or a metal salt as the recovered product. The pilot plant has been designed to work on waste solutions either before or after the modified electrodialysis cell.
Modified electrodialysis (MED) allows a more efficient separation and concentration of ions in aqueous solution from a dilute process stream. An ion exchange resin is incorporated into the feed compartment to increase the transport of the metal ions relative to protons hence improving the current efficiency at low concentrations relative to conventional electrodialysis. The MED results and technology in the Mewaprev project build on those achieved in the earlier Sereni project. Previous applications of enhanced electrodialysis have mostly been on high purity water. In this project the technique has been developed for industrial metal ion containing waste solutions. Laboratory trials have been carried out successfully, proving the techniques at a small scale. A pilot plant has been designed and constructed which integrates with the 3D cathode unit and ITP sensor. The pilot plant has been commissioned at C-Tech and performed even better than the laboratory unit. The pilot plant has been commissioned on site at the industrial users sites in Belgium and is undergoing industrial trials.
In order to create surfaces with new properties, nano-technology is an important new option. Coatings with new structural or functional properties have been applied to ceramic surfaces. The following procedures have been developed through the MEWAPREV project:
Procedure for controlled impregnation of ceramic SLM parts and partial surface modification of porous alumina parts. Pre-treatment/surface activation of alumina in view of varying its hydrophobicity grade.
Procedure for modification of the surface of alumina ceramics in view of increased corrosion resistance and increased surface area. Procedure for grafting various functional groups on oxide surface and ceramic membranes.
Procedure for applying Nafion membranes on ceramic parts.
This nanotechnology is available also for metallic surfaces.
The ITP sensor consists of a channel plate (reservoir, injection and separation channel) and a metallised cover lid (detection unit, high power supply) which are bonded (glued etc.) together. Both plate and lid are made of plastic (polycarbonate). To realise the fine micro-channel structures in polycarbonate we first etched three different channel geometries (different widths and depths) in silicon by using a isotropic plasma etching process (ICP, bulk micromachining). We then transferred the silicon channel surface topology in a nickel injection moulding tool by using a nickel electro-plating process (nickel tool 2mm thick). The goal of the processing chain is to transfer the channel preciseness (which we arrive in silicon) into a "low cost" plastic channel plate. The cover plate (lid) is realised by using original blank CD's. The detection electrodes and the high power unit on the CDs are realised by using a sputtering process for good adhesion starting layers and a additional electro-plating Au-bath for thicker electrodes. Both cover and channel plate are then carefully aligned and bonded together (this work is still in process and needs further attention). A sensor setup system is being established with the following system interfaces: a) high power supply and relays, b) micro-pumps and micro-valves, c) contacting unit (interface chip/high power supply), d) control and e) evaluation soft ware.
A ceramic filter element for Modified ElectroDialysis (MED) is developed. The membrane consists of a high-permeable, functionalised bulk material, grafted with ion-selective groups, covered by functionalized membranes on the outer element surfaces.
%These elements are more robust compared with polymeric membranes and ion exchanger resins, do not swell, and are stable at higher temperatures.
This new technology has received considerable attention during the last decade. The SLM results and technology in the Mewaprev project are built on those achieved in the earlier Sereni project.
The SLM-technique consists of a combined extraction and stripping process. Both process steps occur simultaneously at the interface of a membrane.
The key to this technique is the development of a selective extractant (carrier) which is immobilised in an organic membrane. This carrier enhances the transfer rate and can be selective.
The metal ion in the aqueous phase reacts with the extractant to a complex which diffuses through the membrane and is extracted by an auxiliary component in the strip phase. This mechanism enables the metal ions to be removed in the outer water phase (rinse waters, spent plating solutions down to less than 0.5 ppm or less and concentrated in the inner phase (strip phase) up to several g/l. This technique can be developed to a continuous process for metal salts recovery.
In contrast to the alternative environmental techniques, the PARCOM values can be reached with the Supported Liquid Membrane technique.
A novel isotachophoresis (ITP) injector geometry was designed and was the subject of a joint patent application with Siemens. This design enabled variable volume sample injections to be performed reliably and simply. Prototype devices were fabricated from polymethylmethacrylate (PMMA) using a rapid direct micromachining technique. The use of these microdevices with a purpose designed and constructed fluid handling system (which enabled automatic delivery of samples and electrolytes) allowed the suitability of the devices for on-line monitoring to be assessed. Based on the outcome of this an industrial MEWAPREV monitoring system was designed and constructed which enables on-line at site analysis of aqueous sample streams. Software was specifically written to permit full control of all the equipment required (i.e. HV power supplies, valves, pumps and detectors). In addition extensive work has been carried out on the development of electrolyte systems for separation of numerous metal ions (Ca, Mg, Mn, Cr, Co, Fe, Ni, Zn, Cu). The developed systems were applied to the analysis of provided metal waste streams. Although in this project only metal ions were studied, there is a huge potential market for analysing other ionic species present in industrial process streams. The instrument itself could also be used for analysing process streams from different industries.
Recherche de données OpenAIRE...
Une erreur s’est produite lors de la recherche de données OpenAIRE
Aucun résultat disponible