Chemical waste streams

Only air is needed as an auxiliary chemical. Waste streams which might cause a pollution problem or effect the commercial feasibility are excluded. 

Search the Internet for information on chemical waste streams (both the US EPA and the EU have excellent websites on this subject), and suggest an eco-friendly active catalyst and a support for each of the three options. Suggest two methods for characterizing your catalysts before and after the reaction, and one method for characterizing at least one of the catalysts during the reaction (see the literature on operando spectroscopy [29]). 

The Environment Report (Reference 14.4) defines the operational non-radiological impacts. This includes the impact of cooling and analysis of chemical waste streams. 

The process is designed from a knowledge of physical concentrations, whereas aqueous effluent treatment systems are designed from a knowledge of BOD and COD. Thus we need to somehow establish the relationship between BOD, COD, and the concentration of waste streams leaving the process. Without measurements, relationships can only be established approximately. The relationship between BOD and COD is not easy to establish, since different materials will oxidize at different rates. To compound the problem, many wastes contain complex mixtures of oxidizable materials, perhaps together with chemicals that inhibit the oxidation reactions. 

The thermal degradation of mixtures of the common automotive plastics polypropylene, ABS, PVC, and polyurethane can produce low molecular weight chemicals (57). Composition of the blend affected reaction rates. Sequential thermolysis and gasification of commingled plastics found in other waste streams to produce a syngas containing primarily carbon monoxide and hydrogen has been reported (58). 

The radicals are then involved in oxidations such as formation of ketones (qv) from alcohols. Similar reactions are finding value in treatment of waste streams to reduce total oxidizable carbon and thus its chemical oxygen demand. These reactions normally are conducted in aqueous acid medium at pH 1—4 to minimize the catalytic decomposition of the hydrogen peroxide. More information on metal and metal oxide-catalyzed oxidation reactions (Milas oxidations) is available (4-7) (see also Photochemical technology, photocatalysis). 

Dead Sea Works Process. The Dead Sea Works, a subsidiary of Israel Chemicals Ltd., aimounced plans ia 1992 to constmct a 25,000 t/yr magnesium plant at Beer-Sheva, Israel. The plant, to be based on Russian camaHite technology, is designed to use an existing potash plant as the source of camaHte. The chlorine by-product can be either Hquefted and sold, or used ia an existing bromine plant. Waste streams from the camaHite process, as well as spent electrolyte from the electrolytic cells, can be returned to the potash plant. 

The acidic contaminants can also be removed by employing a system that utilizes extractions, precipitation, distillation, and other treatments for rendering the waste stream acceptable for current disposal standards (18—20). First Chemical Corporation uses such a system. Residual nitric acid can be removed by a multistage countercurrent Hquid-Hquid extraction. The nitric acid (ca 25%) is then reconcentrated by distillation for further use. 

Inorganic heavy metals are usually removed from aqueous waste streams by chemical precipitation in various forms (carbonates, hydroxides, sulfide) at different pH values. The solubiUty curves for various metal hydroxides, when they are present alone, are shown in Figure 7. The presence of other metals and complexing agents (ammonia, citric acid, EDTA, etc) strongly affects these solubiUty curves and requires careful evaluation to determine the residual concentration values after treatment (see Table 9) (38,39). 

The two principal methods of softening water for municipal purposes are addition of lime or lime-soda and ion exchange. The choice method depends upon such factors as the raw-water quaUty, the local cost of the softening chemicals, and means of disposing of waste streams. 

In addition to many varied apphcations in the chemical industiy, the reactotherm is widelv used to process waste sludges which must be dried in order to lanc fill the sohd components. In many of these cases, the solvents are valuable components of the waste stream and can be recovered and recycled. 

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