Capacitor Electrolyte Recycling

capacitorsCapacitor electrolytes are high-resistivity, organic (glycol base), liquid solvents with one or more dissolved, ionically conductive solutes. Regardless of the specific chemical composition of the capacitor electrolyte solution used, the desired capacitor electrolyte bath performance can only be achieved when relatively narrow operating limits of pH, water content, conductivity, and contaminant levels (particularly chlorides), are maintained. The chemistry and chemical stability of the capacitor electrolyte bath greatly influences the frequency characteristics and high temperature load life of the capacitors processed in the capacitor electrolyte bath. With time, particularly at elevated temperatures, these capacitor electrolyte bath solutions typically become contaminated with solvent/glycol degradation products and must be discarded. Disposal of spent capacitor electrolyte baths can be costly and wastes a valuable resource that is preferably decontaminated and reused.

EET's patented and patents pending High Efficiency Electrodialysis (HEED®) technology is ideal for reclaiming glycol-based capacitor electrolyte baths. Like traditional electrodialysis, HEED® is an electro-membrane process in which the ions (ionized and ionizable species) are transported through a semipermeable ion exchange membrane from one compartment to another under the influence of an electrical potential. In effect, ions are driven by a direct current electrical field from a region of low concentration to one of high concentration. In the case of capacitor electrolyte baths, ionized or partially ionized degradation acids and other charged species such as inorganic acids (conductive solutes) are transported from the capacitor electrolyte stream and are driven to the concentrate stream. The deionized capacitor electrolyte stream can then be beneficially reused. Very low capacitor electrolyte bath solution conductivities (<10 mS/cm) can be achieved, with total degradation products <250 ppm.

Using HEED® electrodialyisis to reclaim capacitor electrolyte baths allows capacitor manufacturers to lower unit capacitor costs by improving capacitor quality, increasing capacitor production yields, reducing costs for capacitor electrolyte chemicals, and greatly reducing costs for spent capacitor electrolyte bath disposal.

Contact EET for more information.

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