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NH3 recovery by electrochemical application
Ammonia (NH3) is a novel carbon free energy and fundamental nutrients for many biological metabolisms. It is artificially produced by energy-intensive Haber-Bosch process (35-50 MJ/kg N), which take possession of 2% of world total energy consumption with 1.6% of global CO2 emissions. The major use of NH3 is as a fertilizer, which provides essential nutrient, but approximately 30% N-contained fertilizer eventually release into wastewater stream. Such dramatic NH3 runoff not only have a negative effect on bioactivity of microorganisms, which is particularly involved in anaerobic digestion (AD), but leads to eutrophication and other environmental problems. In our laboratory, therefore, electrochemical system, which allows the facile accumulation of a neutral species of NH3, is being performed. When a cation exchange membrane (CEM) is placed between the two electrodes, cations in the anode compartment are transported through the membrane to the cathode compartment for charge neutrality. NH4+ can act as a main charge carrier and be accumulation. This ammonia can be captured by OH-, which is produced by hydrogen evolution reaction (HER) at cathode; It allows cathodic pH to alkaline condition.
Resource recovery from electronic wastes
Electronic device typically contains valuable metals such as Cu, Au, Ag, and Pt. However, periodic replacement of such equipment has been shorter due to the revolution of technology. Recent study reported that electronic wastes (e-wastes) contain precious metals up to ppm unit. Therefore, recovery of these resources which have a great potential is environmental challenge. Our group has been performed the recovery process of metals in e-wastes using novel porphyrin-based porous polymer. Metals is recovered by 3 steps (adsorption, desorption, and metal plating). Hydrometallurgy method is adopted for metal adsorption/desorption, and it can be selectively recovered by the metal plating method in the form of film. Metal plating was conducted by two different electro-based technologies. Electroless process by galvanic reduction which is a coating method by electroless nickel immersion gold (ENIG) has been studied. Moreover, electronic process with electrolytic reduction of metal was conducted.
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