RESEARCH ARTICLE

Reduction of dinitrotoluene sulfonates in TNT red waterusing nanoscale zerovalent iron particles

Shi-Ni Zhu & Guo-hua Liu & Zhengfang Ye &

Quanlin Zhao & Ying Xu

Received: 21 October 2011 /Accepted: 6 January 2012 /Published online: 21 January 2012# Springer-Verlag 2012

AbstractPurpose This research was designed to investigate the fea-sibility of converting the dinitrotoluene sulfonates (DNTS)in TNT red water into the corresponding aromatic aminocompounds using nanoscale zerovalent iron (NZVI).Methods NZVI particles were simultaneously synthesizedand stabilized by sodium borohydride reduction in a non-deoxygenated system. The morphology, elemental content,specific surface area, and crystal properties of the NZVIwere characterized before and after the reaction by envi-ronmental scanning electron microscope; energy dispersiveX-ray; Brunauer, Emmett, and Teller; and X-ray diffrac-tion, respectively. The reduction process was conducted atpH06.3 at ambient temperature. The efficiency of theNZVI-mediated DNTS reduction process was monitoredby HPLC, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analyses.Results The properties of the NZVI particles prepared werefound to be similar to those obtained through oxygen-freepreparation and inert stabilization processes. Both 2,4-DNT-3-sulfonate (2,220 mg L−1) and 2,4-DNT-5-sulfonate(3,270 mg L−1) in TNT red water underwent a pseudo-first-order transformation when mixed with NZVI at room

temperature and near-neutral pH. Their observed rate con-stants were 0.11 and 0.30 min−1, respectively. Within 1 h ofprocessing, more than 99% of DNTS was converted byNZVI-mediated reduction into the corresponding diamino-toluene sulfonates.Conclusions NZVI can be simultaneously prepared and sta-bilized in a nondeoxygenated system. NZVI reduction is ahighly efficient method for the conversion of DNTS into thecorresponding diaminotoluene sulfonates under near-neutralpH conditions. Therefore, NZVI reduction may be useful inthe treatment of TNT red water and subsequent recovery ofdiaminotoluene from explosive wastewater.

Keywords Nanoscale zerovalent iron (NZVI) .

Dinitrotoluene sulfonate . TNT red water . Reduction

1 Introduction

2,4,6-Trinitrotoluene (TNT) red water is an explosive waste-water generated during the purification process of crudeTNT. Direct discharge of untreated TNT red water severelycontaminates soil and groundwater systems, leading to itsclassification as a hazardous waste by EPA (Tsai 1991).Currently, there are many problems associated with thegeneration, treatment, and disposal of TNT red water, in-cluding the high energy consumption and bed agglomera-tion of incineration (Acharya 1997), high temperature andpressure requirements for wet air oxidation (Hao and Phull1993), bio-refractory for biological process (Tsai 1991), andthe hazard from the remaining concentrated solution fromvacuum distillation (Zhao et al. 2010). Although adsorptionhas been widely used to remove a variety of pollutants fromwastewater (Gupta 2006; Gupta and Ali 2008; Gupta andRastogi 2008a, b, c, 2009; Gupta et al. 1997, 2006, 2007a,

Responsible editor: Vinod Kumar Gupta

S.-N. Zhu :G.-h. Liu : Z. Ye (*) :Q. ZhaoDepartment of Environmental Engineering, Peking University,The Key Laboratory of Water and Sediment Sciences,Ministry of Education,Beijing 100871, Chinae-mail: yezhengfang@iee.pku.edu.cn

S.-N. Zhu :Y. XuCollege of Resource and Environment Engineering,Liaoning Technical University,Fuxin 123000, China

Environ Sci Pollut Res (2012) 19:2372–2380DOI 10.1007/s11356-012-0749-8

b, c, 2009), none of these methods can sufficiently degradeimpurities or convert them into nontoxic or biodegradableproducts.

The region isomeric dinitrotoluene sulfonates (DNTS),2,4-dinitrotoluene (DNT)-3-sulfonate and 2,4-DNT-5-sulfo-nate, are the major organic pollutants in TNT red water(Gilbert 1977) owing to their toxicity (Neuwoehner et al.2007; Ju and Parales 2010). Furthermore, due to theelectron-withdrawing effect of their nitro constituents, thesecompounds are difficult to remove by oxidation (Ju andParales 2010). The conversion of the sulfonated derivativesof TNT isomers to the corresponding aromatic amino com-pounds is an important process for reducing the environ-mental impact as the products are less explosive (Keum andLi 2004), more easily oxidized (Kang et al. 2006; Oh et al.2003), and more biodegradable (Oh et al. 2005; Sun et al.2010) than their parents. Moreover, diaminotoluene sulfo-nates can be easily converted into the commercially valuablediaminotoluene, in a 90% yield by hydrolytic desulfonation(Gilbert 1977).

Recently, the active metal, zerovalent iron (ZVI), hasbeen reported to mediate the reductive conversion of nitroaromatic compounds (NACs) to the corresponding aromaticamino compounds (Bandstra et al. 2005). However, directtreatment of TNT red water with ZVI and hydrochloric acidgave only a 40% yield of the corresponding diamino com-pounds (Gilbert 1977). Therefore, development of a highlyefficient method for the conversion of DNTS in TNT redwater into the corresponding diaminotoluene sulfonates isnecessary.

Owing to their size and shape-dependent electronic andcatalytic properties (Li et al. 2006), nanoscale zerovalentiron (NZVI) particles were considered in the short term to bea highly efficient reducing agent. They have been widelyused in the reduction of NACs, especially in the reduction ofrefractory explosives such as nitrobenzene (Khim et al.2001), DNT (Darko-Kagya et al. 2010), TNT (Zhang et al.2009; Jiamjitrpanich et al. 2010), and hexahydro-1,3,5-tri-nitro-1,15-triazine (RDX) (Naja et al. 2008). However, theuse of NZVI to affect a similar conversion in DNTS has notbeen reported.

The aim of this research was to investigate the feasibilityof transforming the DNTS in TNT red water into thecorresponding aromatic amino compounds using NZVI un-der ambient conditions. The NZVI used in this study wassynthesized and stabilized in a nondeoxygenated system.The morphology, elemental content, specific surface area,and crystal properties of NZVI were characterized beforeand after the reaction by environmental scanning electronmicroscope (ESEM), Brunauer, Emmett, and Teller (BET),energy dispersive X-ray (EDX) and X-ray diffraction(XRD) analyses, respectively. The efficiency of the reduc-tion process was analyzed by high-performance liquid

chromatography (HPLC), Fourier transform infrared spec-troscopy (FTIR), and X-ray photoelectron spectroscopy(XPS). Comparison experiments between NZVI and normalZVI (microsize) were also conducted to investigate thedifferences in DNTS reduction.

2 Materials and methods

2.1 Materials

FeSO4·7H2O, NaBH4, H3PO4, absolute ethanol (analyticalgrade), and potassium phosphate monobasic (spectral pure)were purchased from the Sinopharm Chemical Reagent Bei-jing (Beijing, China). 2,4-DNT-3-sulfonate and 2,4-DNT-5-sulfonate were supplied by the Sigma–Aldrich Company(St. Louis, MO). HPLC-grade acetonitrile was provided byFisher Scientific (NJ, USA). Normal iron powders (analyt-ical grade) were purchased from Guangdong Xilong Chem-ical (Shantou, China) and used without further purification.TNT red water was obtained from a chemical plant inWuhan, China.

2.2 Preparation and characterization of NZVI

NZVI particles were prepared by sodium borohydride reduc-tion of Fe2+. Briefly, a 0.15-M aqueous solution of NaBH4

was added dropwise to the same volume of a 0.05-M aque-ous solution of FeSO4·7H2O at room temperature (Glavee etal. 1995). The so-formed solutions were used directly with-out deoxygenation. The reaction products were separatedfrom the mixture by centrifugation, rinsed three times withabsolute ethanol (Wang et al. 2010), dried in a vacuum dryer,and stored in a vacuum desiccator until required.

The surface morphology and elemental compositions ofNZVI particles were analyzed with an ESEM (Quanta 200F,FEI, USA) with an EDX (JED-2300, FEI, USA) microanal-ysis system. The specific surface area of the particles wasmeasured by the BET method with an Accelerated SurfaceArea & Porosimetry System (ASAP2010, MICROMETER,USA). The crystal structure was determined by XRD(DMAX-2400, Rigaku, Japan) using Cu Kα radiation (λ0154.056 pm). The XPS (AXIS-Ultra instrument, KratosAnalytical, England) using monochromatic Al Kα radiation(1,487 eV) was used for surface composition analysis.

2.3 Batch experiments of DNTS transformation

TNT red water was diluted ten times before use and allexperiments were conducted in duplicate at room tempera-ture (25±2°C). Batch experiments were carried out in 100-ml conical flasks with 1 g of NZVI particles and 50 mL ofdiluted TNT red water. Following a 5-min period of

Environ Sci Pollut Res (2012) 19:2372–2380 2373

ultrasonication in an ultrasonic cleaner (40 kHz, 3 L), theflasks were transferred to a shaking incubator and shaken at200 rpm for 1 h. Control experiments (without NZVI) wereconducted in parallel. Periodically, approximately 0.4 mL ofthe supernatant was withdrawn from the conical flask andfiltered through a 0.45-μm nylon film to remove any solids.The filtrates were diluted and centrifuged for analysis ofDNTS concentration by HPLC. When the reaction hadreached completion, the solid and liquid phases in the reac-tion systems were sampled for ESEM, EDX, XRD, XPS,and FTIR analyses. A comparison experiment between nor-mal ZVI and NZVI was also carried out.

2.4 Analytical methods

The concentrations of 2,4-DNT-3-sulfonate and 2,4-DNT-5-sulfonate in TNT red water and their by-products weredetermined by HPLC analysis (Agilent 1100, USA). AnAgilent SB–Aq reverse phase column (250×4.6 mm, Agi-lent, USA) was used with UV detection at 230 nm. Themobile phase consisted of acetonitrile and H3PO4–KH2PO4

buffer, and the flow rate was 1.0 mL min−1 (Preiss et al.2009). The injection volume of each sample was 20 μL.

The reduction products of DNTS in TNT red water wereassessed by FTIR and XPS analyses. The FTIR spectra wererecorded using a spectrometer (spectrum GX, Perkin Elmer,England) over 64 scans with a resolution of 4 cm−1. TheXPS instrument (AXIS-Ultra, Kratos Analytical, England)using monochromatic Al Kα radiation (1,487 eV) was usedto analyze elemental composition and determine the valenceand chemical environment of specific atoms based on therelationship between their chemical shift and molecularstructure.

3 Results and discussion

3.1 Characterization of NZVI

ESEM imagery (Fig. 1a) showed that the surface morphol-ogy of the NZVI particles to be composed of homogeneousspheres with a diameter of 50–100 nm. The measured BETsurface area was 12 m2 g−1. Smaller size particles withbigger BET surface area can contribute to unexpected phe-nomena such as caking and oxidization (Wang et al. 2009,2010). The XPS peaks at around 719.9 (Fe 2p1/2) and706.9 eV (Fe 2p3/2, Fig. 2a) and the diffraction peak at44.6° (Fig. 2b) indicated that the presence of Fe0 within theparticles. These results were in agreement with the findingsof previous studies (Glavee et al. 1995; Nurmi et al. 2005;Zhu and Lim 2007).

In addition, we found that the intensities of the peaks at719.9 and 706.9 eV increased after etching with Ar+ for

2.5 min (about 5 nm penetration, Fig. 2a), which wasconsistent with related reports from the literatures (Zhuand Lim 2007). The atomic ratio of Fe to O increased from0.7:1 to 2.03:1, revealing a ratio similar to the value (2.3:1)provided by EDX analysis, enabling a depth detection ofseveral hundred nanometers. On the basis of the aboveresults, it could be concluded that the NZVI particle had acore/shell structure and with an oxide layer thickness ofseveral nanometers.

Moreover, the oxide shell thickness and iron–oxygenatomic ratio of the NZVI particles prepared in the presentstudy were similar to those of NZVI particles preparedaccording to an oxygen-free and inert stabilization process(Wang et al. 2010). This suggested that the simultaneouspreparation and stabilization of NZVI can be achieved under

Fig. 1 ESEM images of a NZVI and b reacted NZVI

2374 Environ Sci Pollut Res (2012) 19:2372–2380

simplified conditions. This may be due to expulsion ofoxygen from the reaction system by the hydrogen generatedduring NZVI preparation. Furthermore, the residual dis-solved oxygen present in the system would facilitate theforming of the uniform and thin Fe3O4 shell, which wouldprotect NZVI from being further oxidized.

3.2 Transformation of DNTS in TNT red water

The ultrasonication was carried out for 5 min to improve thedispersion of NZVI (Liang et al. 2008). The initial concen-trations of 2,4-DNT-3-sulfonate and 2,4-DNT-5-sulfonate in

the diluted TNT red water (pH06.3) were 2,220 and3,270 mg L−1, respectively. Based on the results of thepre-experiment, the 20-g L−1 charge of NZVI and 1 h reac-tion time conditions were used to provide the optimal re-duction effects. In the control experiments, losses of 2,4-DNT-3-sulfonate and 2,4-DNT-5-sulfonate were found to beless than 2% and 5%, respectively.

3.2.1 Transformation kinetics and process

The transformation kinetics of DNTS is shown in Fig. 3 (a).Within the first 10 min, it can be seen that levels of both 2,4-DNT-3-sulfonate and 2,4-DNT-5-sulfonate decreased quick-ly. Furthermore, after 30 min of the reaction, more than 97%of DNTS were removed. Results showed that temporalchanges in 2,4-DNT-3-sulfonate and 2,4-DNT-5-sulfonateconcentrations followed pseudo-first-order kinetics, follow-ing data fitting with the appropriate equations. Table 2 sum-marizes the calculated results, revealing that 2,4-DNT-3-sulfonate was more resistant to NZVI-mediated reductionthan 2,4-DNT-5-sulfonate. For example, the calculated kobsfor 2,4-DNT-3-sulfonate was 0.11 min−1 (t1/206.3 min),whereas the value for 2,4-DNT-5-sulfonate was 0.30 min−1

(t1/202.3 min). This may be due to a greater steric hindranceeffect of the sulfonic acid group in 2,4-DNT-3-sulfonatecompared with 2,4-DNT-5-sulfonate.

As shown in Fig. 3 (b), intermediates evolved during thereduction process. The majority initially appeared and in-creased in concentration during the first 10 min of theprocess and then decreased and ultimately disappeared after30 min of the reaction with NZVI. All of them were elutedfrom the chromatographic column before DNTS (peaks 4and 5). After 60 min of the reaction, four products wereobserved, with retention times of 2.8, 3.6 (peak 1), 4.9, and

Fig. 2 a Fe 2p photoelectron spectra of NZVI (1), reacted NZVI (2),NZVI after etching with Ar+ for 2.5 min (3), and reacted NZVI afteretching with Ar+ for 2.5 min (4); b XRD patterns of NZVI (1) andreacted NZVI (2)

Fig. 3 Reduction kinetics of DNTS and corresponding product distribu-tion (a). HPLC spectra of TNT red water treated for different time (b)

Environ Sci Pollut Res (2012) 19:2372–2380 2375

6.3 (peak 2) minutes. Among these products, peaks 1 and 2corresponded to the reduction products of 2,4-DNT-5-sulfo-nate and 2,4-DNT-3-sulfonate, respectively, based on theresults of single pollutant experiments in an Fe0/H2O sys-tem. In order to better investigate changes in the relativeconcentration of products during the course of the reaction,the products were quantified by peak area ratio and themaximum of the peak area and plotted against reaction time,as shown in Fig. 3 (a). As can be seen from the figure, theconcentration of the intermediate 3 increased significantlyupon initiation of the reaction, before reaching a maximum at5 min and then rapidly decreasing to a constant level at30 min. In contrast, the concentration of product 2 decreasedduring the first 5 min before increasing to its maximum valueat 60 min. An explanation for this phenomenon may be thatDNTS are adsorbed onto the surface of NZVI particles andreact with Fe0 and other electron donors, such as Fe2+ andhydride/H2 (Gillham and Ohannesin 1994; Jiao et al. 2009),while in contrast their reaction products were diffused intothe solution. The relative concentration for product 1 in-creased linearly with time until reaching a plateau at30 min. Furthermore, no decline (or suspension) stage wasobserved. This result reveals that 2,4-DNT-5-sulfonate ismore susceptible to reduction than 2,4-DNT-3-sulfonate.

The high-resolution XPS spectra of the untreated andtreated samples in the regions of N 1s are shown in Fig. 4.The four peaks at 406.0, 403.2 (NaNO2), 407.2 (NaNO3) ,and 399.5 eV typically present in the XPS spectra of TNTred water disappeared after the treatment with NZVI, andonly one strong peak appeared at 399.5 eV. It was reportedthat the N 1s binding energies of the –NO2 and –NH2 peaksappeared in the regions of 406.2 eV (Hollander et al. 1998)and 399.5 eV (Narushima et al. 2007), respectively. Nopeaks corresponding to inorganic nitrogen were detected,indicating that all nitro groups of pollutants (most of themare DNTS) were reduced to the corresponding amino groupsby NZVI and that NaNO2 and NaNO3 may have been con-verted to N2 or NH3 (Yang et al. 2005). However, it waspossible that the DNTS may have been partly absorbed bythe NZVI and subsequently not reduced. Thus, solid sampleswere also taken after reaction and analyzed by XPS (Fig. 4).In accordance with the XPS spectra obtained for the treatedwater, only one strong peak at binding energy of 399.5 eV(−NH2) was observed in the N 1s photoelectron spectrum.This result confirms that the disappearance of DNTS isabsolutely due to reduction into amino compounds.

3.2.2 Reduction products

Given the complexity of the components in TNT red water,both FTIR and XPS were used to analyze reaction products.The FTIR spectra (Fig. 5) of TNT red water before and afterNZVI treatment were recorded to identify the structure of

the reaction products. Adsorption peaks at 1,481 (N0Ostretching), 1,197 (S0O stretching), 1,045 (C–N stretching),and 671 cm−1 (C–S) were observed in the untreated TNT redwater [Fig. 5 (a)], whereas the peaks for the –NO2 groupdisappeared. Furthermore, new peaks at 3,436 cm−1 (N–Hstretching), 1,628 cm−1 (NH2 bending vibration), and1,366 cm−1 (C–N stretching) appeared in the treated TNTred water [Fig. 5 (b)], suggesting that the nitro groups ofDNTS were reduced to the corresponding amino groups byNZVI.

For further detection of the reaction products of DNTS,XPS spectra of N 1s, C 1s, S 2p, and O 1s were collectedand analyzed. The data were summarized in Table 1. It wasclear that all the functional groups determined by XPS werein accordance with those in diaminotoluene sulfonate. Fur-thermore, the atomic concentration ratio of C, N, and S intreated wastewater was 8.73:2.08:1.00, which is similar tothe ratio (7:2:1) expected of sodium diaminotoluene sulfo-nate. The extra C and N may come from other hydrocarbonsand residual nitroaniline in the TNT red water. Therefore, it

Fig. 4 High-resolution N 1s spectra of organic compounds on thesurface of the reacted NZVI and in the TNT red water before and aftertreatment

Fig. 5 Infrared spectra of TNT red water before (a) and after (b) NZVItreatment

2376 Environ Sci Pollut Res (2012) 19:2372–2380

was concluded that the reduction products of DNTS werethe corresponding sodium diaminotoluene sulfonates, whichwas in agreement with the FTIR analysis.

The oxidation products of NZVI in the reaction systemwere also investigated with XRD and XPS analysis. TheXPS spectra of reacted NZVI before and after etching withAr+ for 2.5 min (Fig. 2a) showed similar peak shapes withbinding energies of Fe 2p 1/20724.4 eV (assigned toFeOOH/Fe2O3) and Fe 2p 3/20711.3 eV (assigned toFe3O4/Fe2O3), although the peak of Fe 2p3/2 ascendedslightly. In the XRD profiles (Fig. 2b), two peaks evidentat M(311) and M(440) were observed together with threesmall peaks at M(220), M(400) and M(511), which wereassigned to Fe3O4/γ-Fe2O3 (Kim et al. 2010; Huang andZhang 2006). The FeOOH might exist in the δ-FeOOHphase, which cannot be identified by the XRD technique(Misawa et al. 1974). The diversity and surface color(Darko-Kagya et al. 2010) of iron oxides in the presentstudy were very similar to the stratified ZVI corrosioncoating observed in a previous study (Huang and Zhang2006). On the basis of the above analyses, it was inferredthat the outer layer of NZVI corrosion coating was mainlycomposed of FeOOH/Fe2O3 and Fe3O4, while Fe3O4 dom-inated in the inner layer.

3.3 Comparison of NZVI with normal ZVI

The competition experiment involving normal ZVI sug-gested that 2,4-DNT-3-sulfonate and 2,4-DNT-5-sulfonatecould not be reduced by normal ZVI directly. The conver-sion rates were less than 1% in both cases after 7 h of ZVItreatment. Since a low pH has been reported to enhance theconversion efficiency of TNT industry wastewater (Barreto-Rodrigues et al. 2009), normal ZVI was also used to reduceDNTS under acidic conditions (initial pH01). The results,presented in Table 2, showed that the rate of the reductionprocess increased after the addition of acid. The concentra-tion of DNTS decreased by 97% after 7 h of reaction with

normal ZVI, but the calculated rate constants were only oneeighth of those obtained with NZVI. N 1s spectra of reduc-tion products revealed that all of the nitro groups in TNT redwater were reduced to the corresponding amino groups(BE0399.5 eV) when treated with NZVI for 1 h, while onlyapproximate 63% of the nitro groups could be reduced bynormal ZVI within 7 h, even under acidic conditions. There-fore, the nanosizing of ZVI is effective for the reductionprocess of DNTS in TNT red water.

It can be seen from Table 2 that the composition of NZVIprepared in this study was similar to that of normal ZVI. TheBET surface area of NZVI was around 30 times greater thanthat of normal ZVI. NZVI was shown to be amorphous,while normal ZVI was crystalline. The significant differ-ences in their BET surface area and solid forms may result indifferent reactivity. This is because the big BET surface areaand small size of NZVI facilitate not only the occurrence ofdirect reduction at the metal surface, but also indirect reduc-tion by the primary oxidization products (Fe2+, hydride/H2)adsorbed on Fe0 (Gillham and Ohannesin 1994; Tratnyekand Johnson 2006; Jiao et al. 2009). The amorphous char-acteristic of NZVI may be another important factor contrib-uting to the high degree of reactivity. This can be explainedby the fact that the surface defects and/or the presence of apoorly ordered structure can act like a catalyst, increasing thereaction rate and iron exploitation and consequently provid-ing the system, in the short term, with an elevated amount ofelectron donors (Comba et al. 2011). Li et al. (2006) alsosuggested that the advantage of NZVI in reducing pollutantscould be correlated to its size and shape-dependent surfacearea and catalytic properties.

In addition, for the normal ZVI, the oxide layer that lies atthe iron–water interface can act as a physical barrier tohindering the reaction of ZVI with contaminants (Scherer etal. 1999). However, the residual nanoparticles observed in theESEM image (Fig. 1b) were shown to be bouffant andhollow, with iron corrosion products spread around them.This suggested that the corrosion for spherical nanoparticlesused in the present study was not a uniform corrosion processof concentric layers of Fe0 and that the corrosion products didnot accumulate to form concentric layers of iron oxides.Thus, unlike normal ZVI, the reducing capacity of NZVIparticles is less likely to be inhibited by corrosion products.On the contrary, the spreading regions of the corrosion prod-ucts are helpful for capturing contaminants, which can bereduced by so-called co-reductants (Noubactep 2008).

4 Conclusions

NZVI was simultaneously prepared and stabilized in a non-deoxygenated system and was subsequently successfullyused to reduce DNTS in the red TNT water. More than

Table 1 Binding energies and assignments proposed to represent thepeaks in N 1s, C 1s, S 2p and O 1s spectra of the treated water

Region Bindingenergy (eV)

Atomratio (%)

Assignment Reference

N 1s 399.6 7.55 R–NH2 Narushima etal. (2007)

C 1s 285.9 31.69 C6H5–NH2 Sundberg et al.(1988)284.8

S 2p 169.7 2.42 RSO2OR Wang et al.(2010)168.6 1.21

O1s 532.2 33.25 C–SO3H Idage et al.(1996)

Environ Sci Pollut Res (2012) 19:2372–2380 2377

99% of DNTS were reduced within 1 h. Kinetic studiesdemonstrated that 2,4-DNT-3-sulfonate (2,220 mg L−1) and2,4-DNT-5-sulfonate (3,270 mg L−1) undergo a pseudo-first-order transformation with observed rate constants of 0.11and 0.30 min−1, respectively when mixed with NZVI (20 gL−1) under near-neutral pH conditions. HPLC analysisshowed that DNTS were rapidly absorbed onto the surfaceof NZVI and gradually reduced. FTIR and XPS analysesindicated that DNTS were converted to the correspondingdiaminotoluene sulfonates. Similar to previous studies, com-parison experiments between NZVI and normal ZVI alsosuggest that the size- and shape-dependent surface area andcatalytic properties were believed to result in the high reac-tivity of NZVI under near-neutral condition, as well as thenonconcentric corrosion behavior observed in this study. Insummary, NZVI reduction was shown to be an efficientmethod for the rapid conversion of DNTS into thecorresponding diaminotoluene sulfonates and may providea promising method for TNT red water treatment.

References

Acharya P (1997) Process challenges and evaluation of bed agglomer-ation in a circulating bed combustion system incinerating redwater. Environ Prog 16(1):54–64. doi:10.1002/ep.3300160121

Bandstra JZ, Miehr R, Johnson RL, Tratnyek PG (2005) Reduction of2,4,6-trinitrotoluene by iron metal: kinetic controls on productdistributions in batch experiments. Environ Sci Technol 39(1):230–238. doi:10.1021/es049129p

Barreto-Rodrigues M, Silva FT, Paiva TCB (2009) Optimization ofBrazilian TNT industry wastewater treatment using combinedzero-valent iron and Fenton processes. J Hazard Mater 168(2–3):1065–1069. doi:10.1016/j.jhazmat.2009.02.172

Comba S, Di Molfetta A, Sethi R (2011) A comparison between fieldapplications of nano-, micro-, and millimetric zero-valent iron forthe remediation of contaminated aquifers. Water Air Soil Pollut215(1):595–607. doi:10.1007/s11270-010-0502-1

Darko-Kagya K, Khodadoust AP, Reddy KR (2010) Reactivity oflactate-modified nanoscale iron particles with 2,4-dinitrotoluenein soils. J Hazard Mater 182(1–3):177–183. doi:10.1016/j.jhazmat.2010.06.012

Gilbert EE (1977) Recovery of organic values from TNT purificationwaste water. Propellants, Explosives, Pyrotechnics 2(6):118–125.doi:10.1002/prep.19770020603

Gillham RW, Ohannesin SF (1994) Enhanced degradation of haloge-nated aliphatics by zero-valent iron. Ground Water 32(6):958–967. doi:10.1111/j.1745-6584.1994.tb00935.x

Glavee GN, Klabunde KJ, Sorensen CM, Hadjipanayis GC (1995)Chemistry of borohydride reduction of iron(II) and iron(III) ionsin aqueous and nonaqueous media—formation of nanoscale Fe,Feb, and Fe2b powders. Inorg Chem 34(1):28–35. doi:10.1021/ic00105a009

Gupta VK (2006) Removal and recovery of the hazardous azo dye acidorange 7 through adsorption over waste materials: bottom ash andde-oiled soya. Ind Eng Chem Res 45(4):1446–1453. doi:10.1021/ie051111f

Gupta VK, Ali I (2008) Removal of endosulfan and methoxychlorfrom water on carbon slurry. Environ Sci Technol 42(3):766–770. doi:10.1021/es7025032T

able

2CharacterscomparisonbetweenNZVIandZVI

Diameter

(μm)

Shape

BETsurfacearea

(m2g−

1)

Crystal

prop

erty

Aromatic

ratio

(%)

Rem

oval

(%)

Pseud

o-first-orderk o

bs

(min

−1)

N1s

spectraof

redu

ction

prod

ucts

eO

CAl

Si

-3-

Sulfonate

-5-

Sulfonate

-3-

Sulfonate

-5-

Sulfonate

BE

(eV)

Area

(%)

NZVIa

0.05

–0.1

Sph

ere

12Amorph

ous

Crystal

4.33

28.33

0.38

6.96

–99

.45

99.82

0.11

0.30

399.5

100

ZVIb

50–10

0Irregu

lar

0.40

5.52

24.75a

0.65

8.04

1.04

97.11

99.67

1.4×10

−2

−3.6×10

−2

399.5

62.95

401.6

16.55

403.6

6.04

406.1

14.46

The

arom

atic

ratio

was

calculated

from

EDX

analysisdata

aReactionfor1hwhentheinitial

pH06.8(w

ithou

tbu

ffer);finalpH

08.7

bReactionfor7hwhentheinitial

pH01(w

ithH2SO4as

buffers);finalpH

05.4

2378 Environ Sci Pollut Res (2012) 19:2372–2380

Gupta VK, Ali I, Saini VK (2007a) Defluoridation of wastewatersusing waste carbon slurry. Water Res 41(15):3307–3316.doi:10.1016/j.watres.2007.04.029

Gupta VK, Ali I, Saini VK (2007b) Adsorption studies on the removalof Vertigo Blue 49 and Orange DNA13 from aqueous solutionsusing carbon slurry developed from a waste material. J ColloidInterface Sci 315(1):87–93. doi:10.1016/j.jcis.2007.06.063

Gupta VK, Carrott PJM, Ribeiro Carrott MML, Suhas (2009) Low-costadsorbents: growing approach to wastewater treatment: a review.Crit Rev Environ Sci Technol 39(10):783–842. doi:10.1080/10643380801977610

Gupta VK, Jain R, Varshney S (2007c) Removal of Reactofix goldenyellow 3 RFN from aqueous solution using wheat husk—an agri-cultural waste. J Hazard Mater 142(1–2):443–448. doi:10.1016/j.jhazmat.2006.08.048

Gupta VK, Mohan D, Suhas SKP (2006) Removal of 2-aminophenolusing novel adsorbents. Ind Eng Chem Res 45(3):1113–1122.doi:10.1021/ie051075k

Gupta VK, Rastogi A (2008a) Biosorption of lead(II) from aqueoussolutions by non-living algal biomass Oedogonium sp. and Nos-toc sp.—a comparative study. Colloids and Surfaces B-Biointerfaces 64(2):170–178. doi:10.1016/j.colsurfb.2008.01.019

Gupta VK, Rastogi A (2008b) Sorption and desorption studies ofchromium(VI) from nonviable cyanobacterium Nostoc muscorumbiomass. J Hazard Mater 154(1–3):347–354

Gupta VK, Rastogi A (2008c) Equilibrium and kinetic modelling ofcadmium(II) biosorption by nonliving algal biomass Oedogoniumsp. from aqueous phase. J Hazard Mater 153(1–2):759–766.doi:10.1016/j.jhazmat.2007.09.021

Gupta VK, Rastogi A (2009) Biosorption of hexavalent chromium byraw and acid-treated green alga Oedogonium hatei from aqueoussolutions. J Hazard Mater 163(1):396–402. doi:10.1016/j.jhazmat.2008.06.104

Gupta VK, Rastogi A, Dwivedi MK, Mohan D (1997) Process devel-opment for the removal of zinc and cadmium from wastewaterusing slag—a blast furnace waste material. Sep Sci Technol 32(17):2883–2912. doi:10.1080/01496399708002227

Hao OJ, Phull KK (1993) Wet oxidation of nitrotoluenesulfonic acid—some intermediates, reaction pathways, and by-product toxicity.Environ Sci Technol 27(8):1650–1658. doi:10.1021/es00045a023

Hollander A, Wilken R, Behnisch J (1998) Nitric oxide radical trap-ping analysis on vacuum-ultraviolet treated polymers. Macromo-lecules 31(22):7613–7617. doi:10.1021/ma9802071

Huang YH, Zhang TC (2006) Reduction of nitrobenzene and forma-tion of corrosion coatings in zerovalent iron systems. Water Res40(16):3075–3082. doi:10.1016/j.watres.2006.06.016

Idage SB, Badrinarayanan S, Vernekar SP, Sivaram S (1996) X-rayphotoelectron spectroscopy study of sulfonated polyethylene.Langmuir 12(4):1018–1022. doi:10.1021/la9503919

Jiamjitrpanich W, Polprasert C, Parkpian P, Delaune RD, Jugsujinda A(2010) Environmental factors influencing remediation of TNT-contaminated water and soil with nanoscale zero-valent iron par-ticles. J Environ Sci Health A Tox Hazard Subst Environ Eng 45(3):263–274. doi:10.1080/10934520903468012

Jiao Y, Qiu C, Huang L, Wu K, Ma H, Chen S, Ma L, Wu D (2009)Reductive dechlorination of carbon tetrachloride by zero-valent ironand related iron corrosion. Appl Catal Environ 91(1–2):434–440

Ju KS, Parales RE (2010) Nitroaromatic compounds, from synthesis tobiodegradation. Microbiol Mol Biol Rev 74(2):250. doi:10.1128/mmbr.00006-10

Kang KH, Lim DM, Shin H (2006) Oxidative-coupling reaction ofTNT reduction products by manganese oxide. Water Res 40(5):903–910. doi:10.1016/j.watres.2005.12.036

Keum YS, Li QX (2004) Reduction of nitroaromatic pesticides withzero-valent iron. Chemosphere 54(3):255–263. doi:10.1016/j.chemosphere.2003.08.003

Khim J, Choe S, Lee SH, Chang YY, Hwang KY (2001) Rapidreductive destruction of hazardous organic compounds by nano-scale Fe-0. Chemosphere 42(4):367–372. doi:10.1016/S0045-6535(00)00147-8

Kim HS, Ahn JY, Hwang KY, Kim IK, Hwang I (2010) Atmospheri-cally stable nanoscale zero-valent iron particles formed undercontrolled air contact: characteristics and reactivity. Environ SciTechnol 44(5):1760–1766. doi:10.1021/es902772r

Li L, Fan MH, Brown RC, Van Leeuwen JH, Wang JJ, Wang WH,Song YH, Zhang PY (2006) Synthesis, properties, and environ-mental applications of nanoscale iron-based materials: a review.Crit Rev Environ Sci Technol 36(5):405–431. doi:10.1080/10643380600620387

Liang F, Fan J, GuoYH, FanMH,Wang JJ, YangHQ (2008) Reduction ofnitrite by ultrasound-dispersed nanoscale zero-valent iron particles.Ind Eng Chem Res 47(22):8550–8554. doi:10.1021/ie8003946

Misawa T, Asami K, Hashimoto K, Shimodaira S (1974) The mecha-nism of atmospheric rusting and the protective amorphous rust onlow alloy steel. Corros Sci 14(4):279–289. doi:10.1016/S0010-938X(74)80037-5

Naja G, Halasz A, Thiboutot S, Ampleman G, Hawari J (2008) Deg-radation of hexahydro-1,3,5-trinitro-1,15-triazine (RDX) usingzerovalent iron nanoparticles. Environ Sci Technol 42(12):4364–4370. doi:10.1021/es7028153

Narushima K, Matsuda N, Mizutani C, Yamashita N, Inagaki N, Lio K,Isono Y, Islam MR (2007) Possibility of solid-state graft copoly-merization on poly(ethylene terephthalate) films by plasma irra-diation and effects of surface modification. Jpn J Appl Phys 46577(7A):4252–4259. doi:10.1143/jjap.46.4252

Neuwoehner J, Schofer A, Erlenkaemper B, Steinbach K, Hund-Rinke K, Eisentraeger A (2007) Toxicological characterizationof 2,4,6-trinitrotoluene, its transformation products, and twonitramine explosives. Environ Toxicol Chem 26(6):1090–1099.doi:10.1897/06-471r.1

Noubactep C (2008) A critical review on the process of contaminantremoval in Fe-0-H2O systems. Environ Technol 29(8):909–920.doi:10.1080/09593330802131602

Nurmi JT, Tratnyek PG, Sarathy V, Baer DR, Amonette JE, Pecher K,Wang CM, Linehan JC, Matson DW, Penn RL, Driessen MD(2005) Characterization and properties of metallic iron nanopar-ticles: spectroscopy, electrochemistry, and kinetics. Environ SciTechnol 39(5):1221–1230. doi:10.1021/es049190u

Oh SY, Chiu PC, KimBJ, Cha DK (2003) Enhancing Fenton oxidation ofTNT and RDX through pretreatment with zero-valent iron. WaterRes 37(17):4275–4283. doi:10.1016/s0043-1354(03)00343-9

Oh SY, Chiu PC, Kim BJ, Cha DK (2005) Zero-valent iron pretreat-ment for enhancing the biodegradability of RDX. Water Res 39(20):5027–5032. doi:10.1016/j.watres.2005.10.004

Preiss A, Bauer A, Berstermann HM, Gerling S, Haas R, Joos A,Lehmann A, Schmalz L, Steinbach K (2009) Advanced high-performance liquid chromatography method for highly polarnitroaromatic compounds in ground water samples from ammu-nition waste sites. J Chromatogr A 1216(25):4968–4975.doi:10.1016/j.chroma.2009.04.055

Scherer MM, Balko BA, Tratnyek PG (1999) The role of oxides inreduction reactions at the metal–water interface. In: GrundlDLSTJ (ed) Mineral–water interfacial reactions, vol 715. pp301–322 doi:10.1021/es00045a023

Sundberg P, Larsson R, Folkesson B (1988) On the core electronbinding energy of carbon and the effective charge of the carbonatom. Journal of Electron Spectroscopy and Related Phenomena46(1):19–29. doi:10.1016/0368-2048(88)80002-1

Sun HW, Xu XY, Gao GD, Zhang ZZ, Yin PJ (2010) A novel integratedactive capping technique for the remediation of nitrobenzene-contaminated sediment. J Hazard Mater 182(1–3):184–190.doi:10.1016/j.jhazmat.2010.06.013

Environ Sci Pollut Res (2012) 19:2372–2380 2379

Tratnyek PG, Johnson RL (2006) Nanotechnologies for environmentalcleanup. Nano Today 1(2):44–48. doi:10.1016/S1748-0132(06)70048-2

Tsai TS (1991) Biotreatment of red water—a hazardous waste streamfrom explosive manufacture with fungal systems. HazardWaste andHazard Materials 8(3):231–244. doi:10.1089/hwm.1991.8.231

Wang Q, Lee S, Choi H (2010) Aging study on the structure of Fe-0-nanoparticles: stabilization, characterization, and reactivity. JPhys Chem C 114(5):2027–2033. doi:10.1021/jp909137f

Wang Q, Snyder S, Kim J, Choi H (2009) Aqueous ethanolmodified nanoscale zerovalent iron in bromate reduction: syn-thesis, characterization, and reactivity. Environ Sci Technol 43(9):3292–3299. doi:10.1021/Es803540b

Yang GCC, Lee H-L (2005) Chemical reduction of nitrate by nano-sized iron: kinetics and pathways. Water Research 39(5):884–894.doi:10.1016/j.watres.2004.11.030

Zhang X, Lin YM, Chen ZL (2009) 2,4,6-Trinitrotoluene reduction ki-netics in aqueous solution using nanoscale zero-valent iron. J HazardMater 165(1–3):923–927. doi:10.1016/j.jhazmat.2008.10.075

Zhao QL, Ye ZF, Zhang MH (2010) Treatment of 2,4,6-trinitrotoluene(TNT) red water by vacuum distillation. Chemosphere 80(8):947–950. doi:10.1016/j.chemosphere.2010.05.004

Zhu BW, Lim TT (2007) Catalytic reduction of chlorobenzenes with Pd/Fe nanoparticles: reactive sites, catalyst stability, particle aging, andregeneration. Environ Sci Technol 41:7523–7529. doi:10.1021/es0712625

2380 Environ Sci Pollut Res (2012) 19:2372–2380