Adsorption of TNT

DNT, and various other NACs adsorbed strongly to aU clay surfaces tested, and that the adsorption was completely reversible. Daun et al. (1998) performed similar adsorption experiments on TNT and its metabolites to a montmorillonitic clay. They confirmed that the adsorption of TNT and two of its metabolites, 2-amino-4,6-dinitrotoluene (2-ADNT) and 4-amino-2,6-dinitrotoluene (4-ADNT), was completely reversible, but the adsorption of a third degradation product,... 

FIGURE 7.20 Adsorption-oxidation and adsorption of TNT. (After Jain, K. and Bryce, A. J., in Carbon Adsorption Handbook, P.N. Chemreisinoff and F. Ellerbusch, Eds., Arm Arbor Science Publishers, Aim Arbor MI, Chapter 17, p. 661. With permission.)... 

The retardation of subsurface transport of TNT arises from this compound s absorption into NOM and adsorption onto mineral siloxane surfaces covered with weakly hydrated cations like potassium (but not sodium and calcium). While components of feldspars exhibit some siloxane surfaces, here we anticipate that most of the silox-anes occur in the aluminosilicate clay minerals (e.g., illite) because these particles have such high specific surface areas (Table 11.3). Hence, the total for TNT may be found at this site ... 

Adsorption by activated carbon is commonly employed for the removal of TNT from aq waste streams, eg, pink water formed in shell-loading operations. Low efficiency in regeneration of the carbon for reuse has led to a study of the factors involved (Ref 99), with conclusions as follows. The TNT is adsorbed at many of the numerous high-energy sites on the surface of the carbon. Basic materials, introduced during activation of the carbon by combustion and oxidation and also present at these sites, then induce oxidation-reduction reactions of the methyl with the nitro groups in the TNT. This is... 

The analysis of TNT in wastewaters is made simple and direct by LC using a UV detector at 220nm (Refs 81 158). An LC method suitable for the low level determination of Tetrvl in the presence of TNT, RDX and HMX is described (Ref 91). The adsorptive LC of TNT was demonstrated using poly(styrene-divinyl benzene) adsorbent and ethanol as the moving phase (Ref 112). HPLC was used for the separation of TNT from purification by-products of hexanitro-bibenzyl (Ref 69). Enzymatic action on TNT was supported by HPLC (Ref 155). HPLC chromatograms of TNT are included, together with data on TLC and color reactions of TNT in mixts (Ref 153). Pollutants in wastewater... 

Haberman J. Sharma, Charcoal Regeneration. Part I. Mechanism of TNT Adsorption , ARLCD-TR-77065, US Army ARRADCOM, Dover (1977) 147) C.A. Heller et al, Detection of... 

As tested in Belgium, the CDC consisted of three main components the detonation chamber, an expansion chamber, and an emissions control unit, the latter comprising a particle filter and a bank of activated carbon adsorption beds (NRC, 2002). The maximum explosive rating of the T-10 mobile unit is 12 pounds of TNT-equivalent, including the donor charge used to access the burster and the agent. 

For deflagration experiments the cantilevers were first exposed to controlled amounts of TNT vapour from the vapour generator. The amount of TNT adsorbed on the cantilever was calculated from the resonance frequency shift using Equation (1). The variation in the resonance frequency of the cantilever due to TNT adsorption is shown in Figure 5. The initial mass of the cantilever was calculated to be approximately 130 ng. 

Later work showed similar adsorption-desorption behavior for NACs in clay types other than kaolinite. The adsorption constant was found to increase fairly uniformly for all tested NACs in the ratio of 1 6 12 (kaolinite iUite montmoril-lonite). This ratio is quite close to the relative surface areas of the three minerals illite and montmorillonite have 6 and 16 times more available surface area, respectively, than kaolinite (Haderlein, Weissmahr, and Schwarzenbach, 1996). This observation suggests that a similar EDA complexation mechanism controls the adsorption of NACs to these minerals as well. The authors also showed that TNT,... 

Sopha, H.I. and Svancara, I. (2014) Determination of TNT at an ex-situ prepared bismuth film electrode using adsorptive stripping voltammetry. An initial study, Sci. Pap. Univ. Pardubice, Sen A, 20, 5 - 20,... 

Complete reduction of TNT and its partially reduced derivatives can also be accomplished when these compounds are present in soil under strict anaerobic conditions (Fig. 14). Notably, after 4 days TNT and partially reduced nitrotoluenes have completely disappeared from the aqueous phase, whereas considerable amounts of these contaminants (approx. 180 mg TNT and 40 mg ADNT per kg ) are still present in soil. Obviously, at these lower levels of contamination the process of desorption becomes slower than the reduction reaction. The reduction of these compounds in heaps or compost piles, where aerobic or semiaerobic conditions prevail, remains incomplete. Products of partial reduction such as mononitro-diamino- and dinitro-monoamino-toluenes and azoxy compounds are extractable from soil. In contrast to the observations made in the absence of soil (Fig. 13), TAT as a product of complete reduction of TNT is irreversibly bound to the soil matrix and thus remains undetectable in the aqueous phase (23). Interestingly, this irreversible binding does not require the participation of O2. Therefore, primary adsorption of TAT corresponds to the well-known mechanism of intercalation of diamines into clay minerals such as montmorillonite (18,48). 

The process of interlamellar adsorption to clay and final humification can also be applied to diaminotoluenes. These are formed by reduction of the respective dinitrotoluenes that are cocontaminants of TNT. The diaminotoluenes are eliminated somewhat more slowly than TAT but in the long run they completely and irreversibly disappear from the aqueous phase (E. Herkner, unpublished). 

Figure 2. Distribution of DNOC (open symbols), and TNT (filled symbols) between aqueous and solid phases of typical aquifer and soil materials. Shown is the fraction of sorbed species as a function of pH and K" -saturation of the clay minerals. The relative importance of the two dominating sorption mechanisms are compared hydrophobic partitioning into sediment organic matter (O, ) and specific EDA-complex formation with clay mineral surfaces (O, ) triangles (A, A) represent the overall speciation for DNOC and TNT respectively. Sediment parameters were chosen as follows fraction of organic carbon 4. (soil) = 0.05 f (aquifer) = 0.001 fraction of clay minerals f igy (soil) = 0.35 fciay (aquifer) = 0.05 porosity e(soil) = 0.4 (aquifer) = 0.3 bulk density p(soil) = p(aquifer) = 2.5 kg L water saturation 0(soil) = 0.5 0(aquifer) = 1 fraction of K -saturation of clay minerals = 0.001 (when pH was used as system variable) pH = 7.0 (when f(, +, was used as system variable). Linear adsorption isotherms of TNT and... 

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