Environmental exchange

D. H. Williams, and I. Fleming, Line broadening and environmental exchange, 5 ed. University Press Cambridge, (1995), pp 102-105. 

Auliff, Lily. "Powering the Future." CEC Environmental Exchange June 2001 http //cechouston.org/newsletter/2001/nl 06-01/power.html US Army Corps of Engineers. "Site Evaluation for Application of Fuel Cell Technology." ERDC/CERL TR-01-41. April 2001... 

Life cycle inventory (LCI) is a methodology for estimating the consumption of resources and the quantities of waste flows and emissions caused or otherwise attributable to a product s life cycle [3]. The inventoiy analysis constitutes a detailed compilation of all of the environmental inputs and outputs to each stage of the life cycle [10]. The inventory usually includes raw material and energy consumed, emissions to air and water, and solid waste produced. The processes within the life cycle and the associated material and energy flows as well as other exchanges are modelled to represent the product system and its total inputs and outputs from and to the natural environment, respectively (Fig. 8.2). This results in a product system model and an inventory of environmental exchanges related to the functional unit. 

The structure and interfacial association of the full-length vesicle SNARE, synaptobrevin (I), were compared in 4 different lipid environments using NMR and ESR spectroscopy. In micelles, segments of the SNARE motif were helical and associated with the interface. However, the fraction of helix and interfacial association decreased as I was moved from micelle to bicelle to bilayer environments, indicating that the tendency toward interfacial association was sensitive to membrane curvature. In bilayers, the SNARE motif of I transiently associated with the lipid interface, and regions that were helical in micelles were in conformational and environmental exchange in bicelles and bilayers. ... 

Ohta and Tanaka reported a method for the simultaneous analysis of several inorganic anions and the cations Mg + and Ca + in water by ion-exchange chromatography. The mobile phase includes 1,2,4-benzenetricarboxylate, which absorbs strongly at 270 nm. Indirect detection of the analytes is possible because their presence in the detector leads to a decrease in absorbance. Unfortunately, Ca + and Mg +, which are present at high concentrations in many environmental waters, form stable complexes with 1,2,4-benzenetricarboxylate that interfere with the analysis. 

A simplified schematic layout of an ion-exchange production facihty is presented in Figure 1. Layouts vary from one company to another and are significantly more complex when recycle of streams and environmental controls are incorporated in the schematics. 

Historically the United States was a primary exporter of ion-exchange resin. As of 1994, the United States imports substantially more than it exports. Because compliance with tightening environmental regulations in the United States impacts on the cost of manufacture, offshore resin is most often lower in price. 

Waste Treatment. Environmental concerns have increased the need to treat Hquid discharges from all types of industrial processes, as well as mnoffs where toxic substances appear as a result of leaks or following solubilization (see Wastes, industrial). One method of treatment consists of an ion-exchange system to remove the objectionable components only. Another involves complete or partial elimination of Hquid discharges by recycling streams within the plant. This method is unacceptable unless a cycHc increase in the impurities is eliminated by removing all constituents prior to recycling. 

The production of ketene by this method has no significant environmental impact. The off-gases from the ketene furnace are either circulated to the furnace and burned to save energy or led to a flare system. The reaction can also be carried out at 350—550°C in the presence of alkaH-exchanged zeoHte catalysts (54). Small quantities of ketene are prepared by pyrolysis of acetone [67-64-1] at 500—700°C in a commercially available ketene lamp (55,56). 

The aqueous sodium naphthenate phase is decanted from the hydrocarbon phase and treated with acid to regenerate the cmde naphthenic acids. Sulfuric acid is used almost exclusively, for economic reasons. The wet cmde naphthenic acid phase separates and is decanted from the sodium sulfate brine. The volume of sodium sulfate brine produced from dilute sodium naphthenate solutions is significant, on the order of 10 L per L of cmde naphthenic acid. The brine contains some phenolic compounds and must be treated or disposed of in an environmentally sound manner. Sodium phenolates can be selectively neutralized using carbon dioxide and recovered before the sodium naphthenate is finally acidified with mineral acid (29). Recovery of naphthenic acid from aqueous sodium naphthenate solutions using ion-exchange resins has also been reported (30). 

Chromium Removal System. Chlorate manufacturers must remove chromium from the chlorate solution as a result of environmental regulations. During crystallization of sodium chlorate, essentially all of the sodium dichromate is recycled back to the electrolyzer. Alternatively, hexavalent chromium, Cr, can be reduced and coprecipitated in an agitated reactor using a choice of reducing agents, eg, sodium sulfide, sulfite, thiosulfate, hydrosulfite, hydrazine, etc. The product is chromium(III) oxide [1333-82-0] (98—106). Ion exchange and solvent extraction techniques have also... 

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