Isolation waste streams

One of the methods used to isolate succinic acid from the waste stream of the adipic acid process is esterification of the mixture of succinic, glutaric, and adipic acid followed by fractionation (65—69). 

If the waste stream has a high content of fine particulate matter then, by isolating piarticulate matter, most of the contamination would be isolated. 

The size of the particles, the medium, and the contaminant are all important factors in the selection of a separation technique. Another important consideration in selecting a separation technique is whether the process is intended to make the waste stream uniform or to isolate a portion of the waste stream for treatment. 

A green chemistry variation makes use of solventless conditions to minimize the waste stream from reactions of this type. To a mortar are added aldehyde 67, ketone 68 and solid sodium hydroxide. The mixture is ground and within 5 minutes aldol product 69 is produced. Addition of the second ketone and further grinding affords the 1,5-diketone 70, which can be isolated and cyclized to pyridine 71 with ammonium acetate. The authors report that this method can substantially reduce the solid waste (by over 29 times) and is about 600% more cost effective than previously published procedures. 

As a model metathesis reaction, diethyl diallyhnalonate was cychzed in the presence of 5 mol% (41) within forty minutes in methylene chloride at 40 °C the product was isolated as a colorless oil after filtration and removal of volatiles. An analogous reaction with the soluble catalyst (29) was complete in less than five minutes, suggesting that metathesis reactions catalyzed by (41) are diffusion-controlled. Nonetheless, a reaction time of forty minutes is reasonable, and the validation for this chemistry lies in the simplified purification procedure and minimization of waste streams. 

The results of this study are summarized in Table 4. The product is isolated by filtration of the reaction mixture through a silica column, thus avoiding an aqueous waste stream. 

Thermal desorption treatment is generally considered to be an alternative to incineration. Thermal desorption operates at much lower temperatures than incineration and keeps the heating systems independent of the wastes, which minimizes off-gas production. The technology can be used as a waste minimization process, isolating and concentrating waste constituents, or as a product recovery process. Thermal desorption can also be used to separate contaminants in mixed waste streams by removing volatile constituents. 

Isolation of Flavouring Materials from Waste Streams... 

This process is also used to obtain very highly concentrated, high-quality isolates from plant juices [23] and the recovery of volatiles from waste streams, notably apple or berry pumice, citrus and onion waste [22]. For example, the see is claimed to efficiently recover more than 90% of the citrus essential oils traditionally lost with the centrifuge waste [22]. 

The highly selective biocatalytic reactions afford a substantial reduction in waste. The overall isolated yield is greater than 90%, and the product is more than 98% chemically pure with an enantiomeric excess of >99.9%. All three evolved enzymes are highly active and are used at such low loadings that counter-current extraction can be used to minimize solvent volumes. Moreover, the butyl acetate solvent is recycled with an efficiency of 85%.The E factor (kgs waste per kg product) for the overall process is 5.8 if process water is excluded (2.3 for the reduction and 3.5 for the cyanation) [47]. If process water is included, the E factor for the whole process is 18 (6.6 for the reduction and 11.4 for the cyanation). The main contributors to the E factor are solvent losses which accounted for 51% of the waste, sodium gluconate (25%), NaCl and Na2SO4 (combined circa. 22%). The three enzymes and the NADP cofactor account for <1% of the waste. The main waste streams are aqueous and directly biodegradable. 

Environmental process analysis requires the characterization of chemical process and waste streams in order to evaluate their environmental abuse potential and treatability characteristics. An integral part of this analysis, as well as environmental fate determinations, is the isolation of organic compounds and metabolic products from very complex matrices such as waste water effluents, process streams, biological reactors, and fermentation broths. Generally, the organics involved are fairly polar, water-soluble compounds that must be ex-... 

The waste streams may be disposed safely if they do not contain contaminants that are harmful to living beings. Several waste streams, however, contain harmful chemicals that enter the human body through the food chain via soil or water or the air that we breathe. These contaminants may be toxic chemicals or radioactive. The former is referred to as hazardous , and the latter as radioactive . Both need treatment to isolate the contaminants from the groundwater, air, and soil prior to disposal. Treatment of hazardous waste streams is the subject of this chapter, while treatment of radioactive wastes, or those containing both hazardous and radioactive contaminants ( mixed wastes), is discussed in Chapter 17. 

In most waste streams, either hazardous or radioactive, only a small amount of harmful contaminants is found in a large volume of otherwise harmless waste, and the treatment is aimed at reduction of the effect of these contaminants on the environment. Possible treatments include separation and recycling of the contaminants, destruction of the waste, and if these methods fail, isolation of the entire waste volume and disposal or safe storage. The decontamination and recycling of waste is a good strategy, provided it is economical. Where recycling is not economical, destruction of the wastes takes precedence over any... 

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