Reactive media

Yu. V. Moiseev and G. E. Zaikov, Chemical Resistance of Polymers in Reactive Media, Plenum Press, New York, p. 586 (1987). 

AM Healy, OI Corrigan. Predicting the dissolution rate of ibuprofen-acidic excipient compressed mixtures in reactive media. Int J Pharm 84 167-173, 1992. 

Catalytic use of these compounds revealed an activity comparable to the titanium species. The most important points of this work are that under the experimental conditions there is no metal loss in solution (a rare cases in heterogeneous catalysis with such reactive media) and that the reaction is completely heterogeneous (Figure 3.29). 

Massachusetts Military Reservation, Falmouth, Massachusetts. Colder Associates Corporation is also involved in a full-scale pilot project at the Massachusetts Military Reservation (MMR), near Falmouth, Massachusetts. Two permeable barriers were emplaced at the site using hydraulic fracturing. Installation cost of the demonstration was estimated to be 160,000. This cost included design, construction, and the reactive media (D206235, p. 2). 

For PRBs using zero-valent iron, the cost of the reactive media can be estimated based on a density of about 2.83 kg of media per meter and a cost of approximately 440 to 500 per ton. An installation cost between 2500 and 8000 per liter for each minute of treatment capacity is a rule-of-thumb for estimating capital cost. Because the elemental iron treatment wall is patented, a site licensing fee is often required. O M costs are generally estimated to range from 1.30 and 5.20 per 1000 liters of treated water (D16068I). Costs for several metal-based PRB deployments are given in Table 1. 

At the Dover Air Force Base in Delaware, a Waterloo Barrier was emplaced as part of a funnel-and-gate system in 1998. The sheet piles extended to a depth of 45 ft and were keyed to a clay aquitard. The total costs for the funnel-and-gate PRB were 800,000. This figure included design, construction, materials, and the reactive media (D206097, p. 1). 

GeoSiphon has several potential limitations and will not be applicable at all sites. Groundwater at a site must demonstrate a difference in hydraulic head in order for the system to operate. In addition, fluctuations in the water table may inhibit the system s performance. The technology may not be applicable at sites with deep contamination and nonsurficial aquifers. When iron is used as the reactive media, performance may also be limited by factors such as pH and high nitrate levels in groundwater. 

Lazman, M. Z., and Yablonskii, G. S., Kinetic polynomial A new concept of chemical kinetics. Patterns and Dynamics in Reactive Media, The IMA Volumes in Mathematics and its Applications, pp. 117-150, Berlin, Springer (1991). 

Bifurcation and global stability in surface catalyzed reactions using the Monte Carlo method (with D.G. Vlachos and L.D. Schmidt). In H. Swinney, R. Aris, and D. Aronson (eds.), Patterns and Dynamics in Reactive Media, (Vol. 37, pp. 187-206). New York Springer-Verlag, 1991. 

In general terms, the reactive media for a PRB should be benign to subsurface environments and should not inhibit bioactivity. In addition, the reactive media should be efficient for a sufficiently long period to reduce costs. The... 

Trench emplacement involves trenching and filling in the fully saturated zone due to problems of immediate water intrusion and potential collapse of the trench walls. Unless subsurface constructions (sheetpile walls, trench filling with biodegradable slurries such as guar, etc.) are utilized, the aquifer materials must be removed and the reactive media emplaced nearly simultaneously. This rapid process of aquifer material removal and reactive media emplacement is possible using continuous trenching devices. 

Groundwater/contaminant residence time per unit thickness of reactive media... 

Update on CARS Diagnostics of Reactive Media at ONERA... 

There are two types of metals that are of interest as reactive media in PRBs (1) corrodable, base metals, which have equilibrium potentials for dissolution that are below the potential for reduction of water or any strongly oxidizing solutes, and (2) noble, catalytic metals, which are not subject to oxidative dissolution under environmental conditions but which participate in reduction of solutes as catalysts. The corrodable, base metals (Fe, Zn, Sn, etc.) are discussed in Sec. III.A, and the role of noble, catalytic metals (Pd, Ni, etc.) in PRBs is discussed in Sec. III.B. 

Most of the experimental research concerning CMRs has been made at the laboratory scale, with experiments of short duration. Little is known about the effect of long term operation on the stability of membranes in CMRs thermal resistance in the reactive media, mechanical integrity, and fouling by carbon deposits or side reactions are all parameters which require improved knowledge to assess the industrial future of CMRs. 

Feinberg, M., Some recent results in chemical reaction network theory. In Patterns and Dynamics in Reactive Media, IMA Volumes on Mathematics and its Applications, Springer-Verlag, Berlin, 1991a. 

The best approach for the identification of natural product leads is a matter of debate. Some very inventive techniques have been used in the bioassay-guidedmethod for example, by spraying TLC plates with reactive media that respond by producing a color change in the presence of an active compound. An alternative is to use an ethnobotanical or ethno-pharmacologicaltechnique, whereby the accumulated wisdom of many generations of native plant users may be harnessed in the... 

In such reactive media branched clusters which do not contain fully condensed metal oxide cores are formed by kinetically limited growth processes. The structure of these clusters can be described using the fractal concept in which a mass fractal dimension D relates the cluster mass M to its radius according to... 

For silica gels a number of parameters have been demonstrated to have a large effect on the evolution of porosity and subsequently on the resulting silica materials [1]. Almost dense, micro- or mesoporous silica materials can be obtained depending on the experimental conditions in which hydrolysis and condensation reactions of silicon alkoxides are carried out. This is not the case for transition metal alkoxides which are very sensitive to hydrolysis. They do not cillow the adaptation of sol-to-gel transition in order to obtain controlled porous textures. Some years ago special attention was paid to the utilization of amphiphilic systems as reactive media to control hydrolysis and condensation kinetics with transition metal alkoxides [37]. In a more recent work Ayral et al. 

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