Electrolysis 122 Waste

The only difference between the two operations (fuel cells and electrolyzers) is that electrolysis increases the entropy therefore, not all the energy needs to be supplied in the form of electricity, as the environment contributes 48.7 kj of thermal energy. Therefore, during electrolysis, waste heat can be provided to furnish the required thermal energy. 

Significant amounts of cryoHte are also recovered from waste material ia the manufacture of aluminum. The carbon lining of the electrolysis ceUs, which may contain 10—30% by weight of cryoHte, is extracted with sodium hydroxide or sodium carbonate solution and the cryoHte precipitated with carbon dioxide (28). Gases from operating ceUs containing HF, CO2, and fluorine-containing dusts may be used for the carbonation (29). 

Potential fusion appHcations other than electricity production have received some study. For example, radiation and high temperature heat from a fusion reactor could be used to produce hydrogen by the electrolysis or radiolysis of water, which could be employed in the synthesis of portable chemical fuels for transportation or industrial use. The transmutation of radioactive actinide wastes from fission reactors may also be feasible. This idea would utilize the neutrons from a fusion reactor to convert hazardous isotopes into more benign and easier-to-handle species. The practicaUty of these concepts requires further analysis. 

Saline Water for Municipal Distribution. Only a very small amount of potable water is actually taken by people or animals internally, and it is quite uneconomical to desalinate all municipally piped water, although all distributed water must be clear and free of harmful bacteria. Most of the water piped to cities and industry is used for Htfle more than to carry off small amounts of waste materials or waste heat. In many locations, seawater can be used for most of this service. If chlorination is requited, it can be accompHshed by direct electrolysis of the dissolved salt (21). Arrayed against the obvious advantage of economy, there are several disadvantages use of seawater requites different detergents sewage treatment plants must be modified the usual metal pipes, pumps, condensers, coolers, meters, and other equipment corrode more readily chlorination could cause environmental poUution and dual water systems must be built and maintained. 

In the results the emissions of mercury appear to have a very substantial contribution for the human toxicity impact score. These emissions are caused by the coproduction of chlorine and sodium hydroxide by electrolysis using a mercury cell. However, this technique is phased out. Therefore, the process descriptions in the Ecoinvent database do not represent up to date technology. In the Ecoinvent database the process for PVC production, in which chlorine is used as one of the compounds, is an aggregated processes based on, seemingly outdated, data from PlasticsEurope. These outdated data also influence the impacts related to waste treatment by incineration because sodium hydroxide is necessary for the waste incineration process. 

The use of electrochemical methods for the destruction of aromatic organo-chlorine wastes has been reviewed [157]. Rusling, Zhang and associates [166, 167] have examined a stable, conductive, bicontinuous surfactant/soil/water microemulsion as a medium for the catalytic reduction of different pollutants. In soils contaminated with Arochlor 1260, 94% dechlorination was achieved by [Zn(pc)] (H2pc=phthalocyanine) as a mediator with a current efficiency of 50% during a 12-h electrolysis. Conductive microemulsions have also been employed for the destruction of aliphatic halides and DDT in the presence of [Co(bpy)3]2+ (bpy=2,2 -bipyridine) [168] or metal phthalocyanine tetrasulfonates [169]. 

Lantagne and Velin [267] have reviewed the application of dialysis, electrodialysis and membrane cell electrolysis for the recovery of waste acids. Because of the new trends governed by environmental pressures, conventional treatment methods based on neutralization and disposal are being questioned. Membrane and electromembrane technologies are considered to be potential energy-efficient substitutes for conventional approaches. Paper mills will focus on the application of ion-exchange membranes namely dialysis, electrodialysis and membrane cell electrolysis for recovery of waste acids. 

Lantagne G, Velin AP, Overview of the application of dialysis, electrodialysis and membrane cell electrolysis for the recovery of waste acids, in ref (45a), and references therein... 

Beaudry EG, Electrolytic separation technology for treating ionic wastes, slurries and process streams 4th Int. Forum on Electrolysis in the chem Jud, For Lauderdale, FL,. 1990 through (278)... 

In the electrolysis plant of Akzo Nobel in Rotterdam a hypochlorite production unit is in operation. This unit has two functions handling chlorine-containing waste gases from the plant and production of hypochlorite. The reaction is carried out in a two-step apparatus in which a liquid jet-loop reactor and a packed column are in series. In this way chlorine is converted to hypochlorite and emissions of chlorine to the atmosphere are avoided. 

For the first decades, all roadmaps show a focus on fossil-based hydrogen production options, mainly onsite and decentral steam methane reformers (SMR), electro-lysers and hydrogen as a by-product from the chemical industry. In some regions, hydrogen is also produced to a certain extend by nuclear, electrolysis, biomass and waste gasification. Later on, with a significant increase of hydrogen, the production... 

Solid Oxide Electrolysers (SOE) are in development for steam electrolysis. As electrolysis is an endothermic process, a supply of waste heat can be used beneficially to reduce the electrolyzer voltage, and thus increase its electrical efficiency. Combination with nuclear power generation and geothermal heat sources is often encountered in development programs for SOE. 

Development of hydrogen production via electrolysis from electricity generated by wind energy. Biohydrogen. Hydrogen production by fermentation using wastes. 

This technology removes dissolved metals from liquid wastes at a lower cost then other treatment options, such as precipitation followed by clarification and conventional filtration, ion exchange, reverse osmosis, and electrolysis. An advantage of the DuPont/Oberlin microfiltration technology is that it produces a dry, stabilized cake that can be landfiUed when used in conjunction with a filter aid/cake stabilizing agent. 

The electrolysis of a mixture of ZnCl2 with alkaline chlorides and the effect of different elements were investigated as a method to extract zinc from ores and industrial wastes. The studies on electrolysis of ZnCl2 in molten ZnCl2-KCl-NaCl... 

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