Removal Of Trinitrotoluene Research Articles

Effects of Nanoscale Zero-Valent Iron on Soil-Leaching of Trinitrotoluene Contaminated Soil in Acid Rain Conditions

The study of effects of nanoscale zero-valent iron (nZVI) on soil-leaching of trinitrotoluene (TNT) contaminated soil in the acid rain conditions is aim to the determination of the effect of nZVI which used as treatment material on soil leaching of TNT contaminated soil in raining condition. Research methodology, soil leaching batch reactor was designed for TNT remediation in soil with nZVI. The reactor was divided into three compartments for the different series of the experiment. Three compartments of the experiments were used for 1) TNT-contaminated soil column (without leaching), 2) TNT-contaminated soil was leached with rainwater, and 3) TNT-contaminated soil was mixed with nZVI and leached with rainwater. The leachants in the experiment were distilled water (pH 6-6.5) and artificial rainwater (pH≈5). The results of this study found the highest TNT removal efficiency was obtained from in the leaching column with nZVI, followed by the leaching column without nanoparticles and non-leaching column at 100.00, 37.25, and 10.65 % respectively. The leachant (artificial rain) which was slightly acidic in pH could remove some of TNT. The leachant improved solubility and transformation of nitro group in TNT to amino group by H ions addition. The results of the current study can be used to predict the circumstances of leaching TNT on-site in the rainy season.

Optimization and evaluation of the efficiency of sono-Fenton and photo-Fenton processes in the removal of 2, 4, 6 trinitrotoluene (TNT) from aqueous solutions

The adverse health effects of trinitrotoluene (TNT) include allergies, liver and blood damage, and carcinogenesis. The present study aimed to optimize the sono-Fenton and photo-Fenton processes for the removal of TNT from aqueous solutions. TNT removal was evaluated at various pH (acidic, neutral, and alkaline), pollutant concentrations (10, 30, 50, 100, and 120 mg/l), H2O2 concentration (10-80 mM), and ferrous ions (0.5-4 Mm). After the optimization of the parameters, the appropriate UV irradiation time and optimal time of ultrasonic waves were determined for the removal of this compound. TNT concentration was measured using high-performance liquid chromatography. Increased hydrogen peroxide from 10 to 40 mMole/l led to higher TNT degradation (45.3% to 88.4% and 40 to 80 mMole/l), while the removal rate decreased from 88.4% to 79%. At the optimal H2O2 concentration, increased pH (3±0.2 to 11±0.2) decreased TNT decomposition from 88.4% to 23.5%. In addition, increased time (5 to 60 minutes) led to the higher photo-Fenton process efficiency (68.6% to 89%). The maximum photo-Fenton efficiency was achieved in optimal conditions at the TNT concentration of 10 mg/L (97%) and 60 minutes, while the efficiency of the sono-Fenton process in optimal conditions was 100% at 20 minutes. Therefore, it was concluded that the sono-Fenton process was effective in the removal of TNT.

An indole-based smart aerogel for simultaneous visual detection and removal of trinitrotoluene in water via synergistic effect of dipole-π and donor-acceptor interactions

In this study, an indole-based aerogel, 4-AING, was successfully constructed and used in simultaneous visual detection and removal of TNT in aqueous system. The diamino groups in 4-AING endowed it great abilities of recognition and adsorption of TNT through point-to-point electron donor-acceptor (D-A) interaction. On the other hand, by the help of the adjacent indole groups, the detection and adsorption process could be facilitated and promoted via face-to-point dipole-π interaction. The maximum adsorption capacity was up to 168.6 mg g−1 according to the Langmuir model. Furthermore, the 4-AING could be effectively regenerated without significant deterioration in its adsorption performance over 7 consecutive cycles, demonstrating the good reusability of 4-AING. The prepared 4-AING was exhibited an obvious color change from light brown to dark brown in the presence of TNT, which was visualized through naked-eye. A smartphone was applied for the colorimetric quantify the adsorption capacity of TNT with linearity range of 42.8 to 156.0 mg g−1 with the limit of detection of 2.9 mg g−1. The excellent adsorption and detection performances in real TNT wastewaters further confirmed the practical application of 4-AING in real wastewater treatment. These results indicated that 4-AING can be used as a smart material in monitoring water quality and treating wastewater.

Removal of Trinitrotoluene with Nano Zerovalent Iron Impregnated Graphene Oxide

Nano zerovalent iron (nZVI) impregnated reduced graphene oxide (nZVI-rGO) hybrid was prepared via gaseous hydrogen reduction of anhydrous iron(III) chloride (FeCl3) on the surface of thermally exfoliated reduced graphene oxide (rGO) nanosheets without using any toxic reducing agent, surfactant, or stabilizing agent. Characterization of prepared samples was carried out using various techniques. Morphological study showed that prepared rGO possesses a few-layered wrinkled paper-like structures and nZVI particles of ~ 30 nm size were homogeneously dispersed on the surface of rGO nanosheets. Fourier transform infrared (FTIR), X-ray diffraction (XRD), and energy dispersive X-ray spectrometry (EDS) analyses indicated that oxygen-containing functional groups decreased in the order of graphite oxide (GO) > rGO > nZVI-rGO. Removal studies of trinitrotoluene (TNT) were carried out using graphite (G), GO, rGO, and nZVI-rGO with the aid of high-performance liquid chromatography (HPLC). Kinetic models were applied to establish the rate and mechanism of adsorption of TNT on different adsorbents, and intraparticle diffusion model based on initial adsorption characteristics was employed to ascertain mechanism of film and intraparticle diffusion in the adsorption process. The removal rate and adsorption capacity was found to be highest for nZVI-rGO, which renders this adsorbent to be a potential futuristic adsorbent for removal of explosives.

Improved removal of Trinitrotoluene (TNT) from contaminated soil by inducing aerobic process: kinetic and chemical byproducts

This study describes the biological degradation of TNT by using induced aeration. Three plastic reactors were used. In each reactor 3 kg of soil were used. In order to increase the porosity of the soil, sawdust was added to soil. Textile wastewater treatment plant sludge was also added to soil. TNT at the concentrations of 1000 mg/kg of soil was added thereafter. Rhamnolipid biosurfactant at the concentration of 60 mg/L was added to related reactors. Aeration interval was at every 3 to 5 days. Every two weeks, sampling of soil were done to analyze the explosives. Samples were analyzed by HPLC. The results showed that at the end of 120 days, TNT removal efficiency in induced aeration in reactors containing sludge and biosurfactant was 98 percent. COD removal efficiency in induced aeration in reactors amended by rhamnolipid was 58 percent and in reactors to which rhamnolipid was not added was 41 percent. Follow-up kinetic studies revealed that explosives removal follow the pseudo first order reaction. The pseudo first-order rate constants of rhamnolipid amended experiments were at least 3.89 orders of magnitude higher for TNT than those found for experiments without rhamnolipid. Application of Rhamnolipid biosurfactant could have a protective effect against the toxicity of explosives for bacteria. Textile sludge from wastewater treatment plant can decrease the time needed for explosive removal. Growth of bacteria and degradation of explosives showed that explosives have been used as a nitrogen source.

MICROBIAL COMMUNITY CHANGES IN TNT SPIKED SOIL BIOREMEDIATION TRIAL USING BIOSTIMULATION, PHYTOREMEDIATION AND BIOAUGMENTATION

Trinitrotoluene (TNT), a commonly used explosive for military and industrial applications, can cause serious environmental pollution. 28-day laboratory pot experiment was carried out applying bioaugmentation using laboratory selected bacterial strains as inoculum, biostimulation with molasses and cabbage leaf extract, and phytoremediation using rye and blue fenugreek to study the effect of these treatments on TNT removal and changes in soil microbial community responsible for contaminant degradation. Chemical analyses revealed significant decreases in TNT concentrations, including reduction of some of the TNT to its amino derivates during the 28-day tests. The combination of bioaugmentation-biostimulation approach coupled with rye cultivation had the most profound effect on TNT degradation. Although plants enhanced the total microbial community abundance, blue fenugreek cultivation did not significantly affect the TNT degradation rate. The results from molecular analyses suggested the survival and elevation of the introduced bacterial strains throughout the experiment.

Efficiency of Nanoscale Zero Valent Iron in Soil Washing System for Removal of Trinitrotoluene

Efficiency of Nanoscale Zero Valent Iron in Soil Washing System for Removal of Trinitrotoluene

Vetiver grass is capable of removing TNT from soil in the presence of urea

The high affinity of vetiver grass for 2,4,6 trinitrotoluene (TNT) and the catalytic effectiveness of urea in enhancing plant uptake of TNT in hydroponic media we earlier demonstrated were further illustrated in this soil-pot-experiment. Complete removal of TNT in urea-treated soil was accomplished by vetiver at the low initial soil-TNT concentration (40 mg kg −1), masking the effect of urea. Doubling the initial TNT concentration (80 mg kg −1) significantly ( p < 0.002) increased TNT removal by vetiver, in the presence of urea. Without vetiver grass, no significant ( p = 0.475) change in the soil-TNT concentrations was observed over a period of 48 days, suggesting that natural attenuation of soil TNT could not explain the documented TNT disappearance from soil.

Femtosecond laser-induced fragmentation and cluster formation studies of solid phase trinitrotoluene using time-of-flight mass spectrometry

We use surface-femtosecond laser mass spectrometry to study the fragments/products formed when trinitrotoluene (TNT) is subjected to femtosecond laser pulse irradiation and to study the conditions under which TNT is removed from a solid surface. In surface-femtosecond laser mass spectrometry a compound is deposited on a solid substrate and is desorbed into vacuum by femtosecond irradiation forming a plume of ionized and neutral species. The positive or negative ions are then accelerated by an electric potential and allowed to drift in the field-free region of a time-of-flight mass spectrometer. The mass-to-charge ratio of each ion is obtained using the value of the accelerating field and the ion flight time. In this paper we report femtosecond laser mass spectra for the positive ions formed by desorbing TNT with 130 fs pulses centered at 800 nm for fluences ranging from 7 to 1.4 × 10 5 J/m 2. The conditions under which TNT removal and ionization occur are also discussed.

Thermodynamic and Kinetic Behaviors of Trinitrotoluene Adsorption on Powdered Activated Carbons

Regulations on the removal of trinitrotoluene (TNT) from wastewater have become increasingly more stringent, demanding faster, less expensive, and more efficient treatment. This study focuses on the adsorption equilibrium and kinetics of TNT on powered activated carbons (PAC). Three types of PACs (i.e., wood based, coal based, and coconut‐shell based) were studied as functions of temperature and pH. Thermodynamic properties including Gibbs free energy, enthalpy, and entropy, were evaluated by applying the Van't Hoff equation. In addition, the adsorption energy distribution functions which describe heterogeneous characteristics of porous solid sorbents were calculated by using the generalized nonlinear regularization method. Adsorption kinetic studies were carried out in batch adsorber under important conditions such as PAC types, temperature, pH, and concentration. We found that fast and efficient removal of TNT dissolved in water can be successfully achieved by PAC adsorption.

Trinitrotoluene removal in a soil slurry and soil box systems by an oil-degrading mixed bacterial culture

Bioremediation of trinitrotoluene (TNT)-contaminated soil has proven difficult due to the low bioavailability of the contaminant and its resistance to biocatalytic attack, causing slow rates of biodegradation. We have previously described a mixed bacterial culture acclimated and maintained on crude oil-containing medium that is capable of high rates of TNT biotransformation activity with low production of metabolites. We investigated the ability of this culture to bioremediate TNT-spiked soil and artificially weathered soil slurry systems, as well as a soil box system. The culture was able to remove up to 302 ppm (mg/l) of TNT within 24 h in a spiked-soil slurry system, which is among the highest rates of TNT removal reported to date. The toxicity of artificially weathered TNT-spiked soil to Vibrio fischeri decreased over a period of 39 h from a 15-min EC50 of 15.7 to 32.5 ppm. Preliminary results of a soil box system, in which no agitation was used, showed similar TNT removal to the soil slurry system, with 100 ppm TNT being removed within 24 h.

Evaluation of continuous flow‐through phytoreactors for the treatment of TNT‐contaminated water

AbstractThe proof of concept for created wetlands to treat groundwater or industrial water contaminated with trinitrotoluene (TNT) was established using bench‐scale, continuous flow reactors with aquatic plants. Contaminant loadings from 0.0132 to 2.488 g/m3/day were tested on phytoreactors using parrotfeather (Myriophyllum aquaticum) as the plant. Reactor removal efficiency and elimination capacity were linearly related to the load of TNT. An algal reactor was also tested at a loading of 0.9671 g/m3/day and removed 93% of the TNT. Some removal was also found in control reactors that contained no plants and minimized algal growth by shielding them from light. However, the removal efficiencies in the controls were much lower. Transformation products, aminodinitrotoluenes (ADNT) and diaminonitrotoluenes (DANT), were detected in the algae and phytoreactors, but not in the controls, indicating that the TNT was being transformed. However, ADNT persisted in the effluent, representing a reactor‐design issue that must be further investigated. ADNT concentrations in the plant material increased with contaminant loading. TNT was only found in plant tissue at the highest loading of 2.488 g/m3/day. Higher concentrations of ADNT were found in the root of the plant, with approximately equal concentrations in the stem and leaf portions. Ratios of 4‐aminodinitrotoluene (4ADNT) versus 2‐aminodinitrotoluene (2ADNT) were higher in the water phase versus what was found in plant material. Because microbial processes tend to favor the formation of 4ADNT, the higher ratio suggests that the removal of TNT is actually a combination of microbial and phyto processes.

A Study of the Use of Alfalfa (Medicago sativa L.) for the Phytoremediation of Organic Contaminants in Soil

AbstractThis article presents the results of a study that was conducted to determine the effectiveness of using alfalfa (Medicago sativa L.) to enhance the phytoremediation of three different types of chemical contaminants. The chemicals studied were trinitrotoluene (TNT), the polycyclic aromatic hydrocarbon (PAH) pyrene, and the polychlorinated biphenyl (PCB) Aroclor 1248. Experiments were conducted using soils that contained high and low organic matter content. The results indicated that recoveries of pyrene and TNT from soil were highly dependent on the soil organic matter content, while the recovery of PCB was not. Significantly low levels of pyrene and TNT were recovered from all treatments in the soil with 6.3 percent organic matter content compared to recovery levels found in soil with 2.6 percent organic matter. The presence of alfalfa plants had a significant effect on the transformation of TNT and PCB in the low organic matter content soil only and had no effect on the fate of pyrene. In the low organic matter soil, only 15 percent and 17 percent of the initial TNT and PCB levels, respectively, were transformed in the unplanted control soils compared to 66 percent and 77 percent in the alfalfa planted pots. In both soil types, pyrene dissipation could not be attributed to the presence of alfalfa plants. Overall, it was concluded that under high soil organic matter conditions, adsorption and covalent binding to the soil organic matter appeared to be the dominant force of pyrene and TNT removal. The effectiveness of using alfalfa to enhance PCB and TNT transformations was more significant in the lower organic matter soil; thus phytoremediation had a greater effect in soils with lower organic matter content. © 2001 John Wiley &amp; Sons, Inc.

Phyto-removal of trinitrotoluene from water with batch kinetic studies

A series of batch reactor studies were conducted to obtain kinetic data for optimizing phyto-treatment of water contaminated with trinitrotoluene (TNT). A plant screening study indicated that stonewort and parrotfeather were the most effective among the plants tested; parrotfeather being chosen for further testing because it is heartier and easier to cultivate than stonewort. Treatment was reproducible under similar conditions, and sequential formation and breakdown of aminodinitrotoluene (ADNT) and diaminonitrotoluene (DANT) were observed in the aqueous phase. TNT removal rates increased with increased plant density, and removal kinetics increased with increasing temperature up to 34° C. Michaelis–Menton kinetics applied to the phyto-removal of TNT. At concentrations less than 5.5 mg/l TNT, a pseudo-first-order approximation of the Michealis–Menton equation was used with acceptable deviation. Prior exposure to TNT did not appear to have a significant effect on phyto-transformation rates, suggesting that the mechanisms for removal were not induced. Small concentrations of ADNT were found in the plant material, however, TNT was not detected. The results indicated that optimized reactors for the phyto-treatment of contaminated wastewater and groundwater are feasible, increasing degradation rates and decreasing reactor volumes.

Phytoremediation: Modeling removal of TNT and its breakdown products

AbstractContamination of soil and groundwater by trinitrotoluene (TNT) is a widespread problem confronting military bases and ammunition manufacturing facilities throughout the United States. Phytoremediation provides a promising treatment of TNT‐contaminated groundwater and wastewater because many plants contain the necessary enzymes to degrade explosives such as TNT. Two phytoremediation methods are proposed in this article: controlled reactors and constructed wetlands. Controlled reactors provide greater control of operating parameters, a reduced possibility of contaminant migration, control of animals feeding on the plants, and minimization of competition from other plant species. Constructed wetlands have relatively low capital costs, and the wetland becomes a desirable ecological resource. Because cost, as opposed to reactor size, appears to be the most significant factor for military base cleanup, this project focused on the constructed wetland approach.To estimate the disappearance of TNT and its breakdown products from a constructed wetland, a first‐order, nonreversible reaction, plug‐flow, finite‐difference model was developed. Batch scale experiments were conducted to define disappearance kinetics for individual chemical species. The results of the model suggest that reasonably sized wetlands may be used to treat a wastestream with an influent TNT concentration of 2.25 ppm at flow rates ranging from 10 to 5,000 gpm. Economic comparisons to other published costs for competing technologies are promising.

Trinitrotoluene (TNT) as a sole nitrogen source for a sulfate-reducing bacterium Desulfovibrio sp. (B strain) isolated from an anaerobic digester.

A sulfate-reducing bacterium (SRB), Desulfovibrio sp. (B strain), isolated from a continuous anaerobic digester (Boopathy and Daniels, Current Microbiology, 23:327-332, 1991) was found to use 2,4,6-trinitrotoluene (TNT) as sole nitrogen source. This bacterium also used nitrate, nitrite, and ammonium as nitrogen source. A long lag period was noticed when TNT or nitrite was used as nitrogen source. Nitrate, nitrite and TNT also served as electron acceptor in the absence of sulfate for this bacterium. Under nitrogen-limiting condition, 100% removal of TNT was observed within 8 days of incubation. The main intermediate observed was diaminonitrotoluene, which was further converted to toluene via triaminotoluene by reductive deamination process. Under nitrogen-rich conditions (presence of ammonium), TNT was converted to diaminonitrotoluene, and toluene was not produced. This isolate did not degrade TNT all the way to CO2. This study demonstrated the possibility of using this isolate to decontaminate the soil and water contaminated with TNT under anaerobic conditions.

Degradation of munition wastes byPhanerochaete chrysosporium

“Pink water” is a waste-water stream generated by munitions LAP (loading, assembly, and packing) operations. The major components of this waste water are trinitrotoluene (TNT) and cyclotrimethylene trinitramine (RDX) at concentrations of 120-175 mg/L and 25 mg/L, respectively. Currently, pink water is treated by activated carbon adsorption. Removal efficiencies of >99.5% have been reported. However, this treatment method suffers a serious limitation in that the carbon cannot be safely regenerated. Loaded carbon is disposed of by incineration after a single use. We have demonstrated that TNT, RDX, simulated, and actual pink water can be effectively treated byPhanerochaete chrysosporium immobilized on the disks of a rotating biological contractor (RBC) in both batch and continuous modes. Greater than 90% removal of TNT from a simulated pink water was observed in a continuous RBC with a residence time of about 24 h. The disk area required was about 10,000 ft2/gpm (4091 m2/m3h) feed. RDX was amenable to treatment, but RDX removal rates were somewhat slower. A full-scale treatment system was designed on the basis of laboratory data, and a cost analysis was performed. This analysis has shown that biotreatment of pink water can be a cost-effective alternative to carbon adsorption.