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A new strain isolated from activated sludge and identified as Burkholderia vietnamiensis C09V was used to biodegrade crystal violet (CV) from aqueous solution. To understand the degradation pathways of CV, batch experiments showed that the degradation using B. vietnamiensis C09V significantly depended on conditions such as pH, initial dye concentration and media components, carbon and nitrogen sources. Acceleration in the biodegradation of CV was observed in presence of metal ions such as Cd and Mn. More than 98.86C of CV (30 mg l) was degraded within 42 h at pH 5 and 30 °C. The biodegradation kinetics of CV corresponded to the pseudo first-order rate model with a rate constant of 0.046 h. UV-visible and Fourier transform infrared spectroscopy (FTIR) were used to identify degradation metabolites. Which further confirmed by LC-MS analysis, indicating that CV was biodegraded to N, N-dimethylaminophenol and Michler's ketone prior to these intermediates being further degraded. Finally, the ability of B. vietnamiensis C09V to remove CV in wastewater was demonstrated. [ABSTRACT FROM AUTHOR]

This study investigated kaolin-supported nanoscale zero-valent iron (nZVI/K) as a heterogeneous Fenton-like catalyst for the adsorption and oxidation of an azo dye, Direct Black G (DBG). New findings suggest that kaolin as a support material not only reduced the aggregation of nanoscale zero-valent iron (nZVI) but also improved the adsorption of DBG. It consequently improved Fenton oxidation by increasing the local concentration of DBG in the vicinity of nZVI. This was confirmed by scanning electron microscopy and X-ray diffraction for the surface morphology of nZVI/K before and after the Fenton-like reaction. Furthermore, nZVI/K proved to be a catalyst for the heterogeneous Fenton-like oxidation of the DBG process in the neutral pH range. More than 87.22 % of DBG was degraded, and 54.60 % of total organic carbon was removed in the optimal conditions: 0.6 g/L dosage of nZVI/K, 33 mM HO, 100 mg/L initial DBG concentration, temperature of 303 K and pH of 7.06. Finally, it was demonstrated that nZVI/K removed DBG from dye wastewater through the processes of adsorption and oxidation. [ABSTRACT FROM AUTHOR]

The degradation of crystal violet in aqueous solution was investigated using kaolin-supported zero-valent iron nanoparticles (K-nZVI). It was found that K-nZVI with a ratio of kaolin:zero-valent iron nanoparticles (nZVI) at 1:1 was most effective in removing crystal violet. Batch experiments show that more than 97.29 % crystal violet was degraded using K-nZVI, while only 24.36 % was removed using nZVI after reacting for 7 min, where the solution contained 100 mg L crystal violet at pH 6.5. This is due to a decrease in aggregation of Fe nanoparticles and enhanced their reactivity in the presence of kaolin, which was confirmed by the characterization using scanning electron microscopy. X-ray diffraction shows the formation of iron oxide and hydroxide, while UV-Vis spectral shows that the absorption peak of crystal violet was reduced, as well as Fourier transform infrared shows that new bands were formed after K-nZVI reacting with crystal violet. These suggest that degradation of crystal violet by K-nZVI include the oxidation of iron, the adsorption of crystal violet onto the K-nZVI, the transformation of crystal violet to leuko-crystal violet, and finally the cleavage of C=C bond. [ABSTRACT FROM AUTHOR]

In this study, a rapid, sensitive, and fully automated on-line solid phase extraction (SPE)-liquid chromatography (LC)-mass spectrometry (MS) method for the analysis of explosive residues in water, was systematically investigated. First, separation of explosive residues was achieved by reverse-phase chromatography using an XDB-C18 column in 30 min with an eluent containing 0.1% acetic acid, 5 mM ammonium acetate, and methanol. Secondly, atmospheric pressures chemical ionization (APCI) and electrospray ionization (ESI) interfaced with the MS detector were used to examine the explosive residues, indicating that APCI-MS was more suitable than ESI-MS for the detection of explosives. Thirdly, the conditions for on-line SPE, including solvent pH and sample injected volume, were optimized. The calibration curves obtained for all explosives studied were linear in the concentration range 0.5-50 μg L. The detection limits of this method ranged from 0.05 to 0.5 μg L when 4000 μL of sample was on-line pre-concentrated on C18 enrichment column. The recoveries from lake waters spiked with explosive standard solution ranged from 90.5 to 108.0%. The proposed method is simple, fast, and could be applied successfully to the analysis of explosive residues in contaminated water without any further pretreatment. [ABSTRACT FROM AUTHOR]

Metal ions, in the form of their EDTA complexes, can be separated and determined by ion chromatography coupled to inductively coupled plasma mass spectrometry (ICP-MS). However, polyatomic interferences can occur during ICP-MS process and this requires techniques for removing or reducing them. ICP-MS combined with an octopole reaction system was used to reduce polyatomic interferences during the detection of metal ions (55Mn, 56Fe, 59Co, 60Ni, 63Cu, 64Zn, 208Pb) as their EDTA complexes followed by the separation of IC. The results indicated that polyatomic interferences can be reduced for the detection of 56Fe, 60Ni, 63Cu and 64Zn if either helium or hydrogen gas was added to the collision/reaction cell. Hydrogen was preferred since it resulted in higher sensitivity and lower background intensity. The separation of seven metal ions was achieved on an anion-exchange column within 7 min using diammoniumhydrogen phosphate buffer of pH 7.5 as the mobile phase. The detection limits were in the range of 0.1–0.5 μg L−1 with the exception of Fe (5.0 μg L−1) if hydrogen was the reaction gas. The method was applied to the determination of metal ions in natural water samples. [ABSTRACT FROM AUTHOR]

This report describes the extraction of selenium species contained in pharmaceutical tablets using either enzymatic hydrolysis or sodium dodecyl sulphate extraction (SDS). The selenium species were determined by ion chromatography coupled to inductively coupled plasma mass spectrometry. In the enzymatic extraction approach, proteolytic enzymes (protease/lipase) were used in a buffer containing 75 mM Tris–HCl at pH 7.5. It was found that the extraction efficiency was significantly improved relative to the use of the SDS approach. For example, the extraction recovery was more than 80% of total Se, where selenocystine Se-methyl-selenocysteine (SeMC) and selenomethionine (SeMet) in the samples were extracted. In contrast, chemical extraction of Se using SDS gave only 60% of total Se, while only two species, SeMC and SeMet, were found. In addition, SeMC was found to be unstable and degraded through oxidation in the extraction solution. Finally, the two enzyme methods were applied to commercial pharmaceutical tablets. [ABSTRACT FROM AUTHOR]

Ion-exclusion chromatography (IEC) coupled with electrospray ionization quadrupole mass spectrometry (ESI-MS) has been used for the analysis of carboxylic acids. The use of ESI-MS provides increased specificity and sensitivity compared to existing detection methods. This paper applies IEC-ESI-MS to the analysis of carboxylic acids in commonly found root exudates and shows that the separation of nine carboxylic acids (pyruvic, oxalic, lactic, malonic, maleic, succinic, tartaric, aconitic and citric acids) can be achieved by IEC within 8 min. The ESI provided reasonable signals from negative ions, [M−H]− in the negative ionization mode. Linear plots of peak area versus concentration were obtained in the range 50–25,000 μg L−1 for MS detection under optimized MS conditions. The detection limits of target organic acids, based upon signal to noise ratio (S/N = 3), ranged from 10 to 30 μg L−1. The reproducibility of peak areas was <2.5% ( n = 5). The proposed method was used for the confirmation and quantification of carboxylic acids in nutrient solutions containing root exudates. [ABSTRACT FROM AUTHOR]

The effectiveness of cosolvent soil flushing and fungal biosorption for the remediation of p,p′-DDT-contaminated soil was evaluated using packed soil columns in order to simulate an in situ soil flushing technique. Greater than 95% of p,p′-DDT (940 mg kg-1) was desorbed from the soil by flushing with 40 or 80% 1-propanol. Increasing the cosolvent volume fraction increased the rate of p,p′-DDT removal from the soil, however, the extent of p,p′-DDT removal was not enhanced. A further enhancement in the rate of p,p′-DDT removal was achieved by increasing the cosolvent flow rate from 6 ml hr-1 to 12 ml hr-1 (pore water velocity from 18.9 to 37.8 cm hr-1). The desorbed p,p′-DDT was removed from cosolvent wash solutions by partitioning onto fungal biomass. Biosorption of p,p′-DDT resulted in low concentrations of the organochlorine (3.3 μg ml-1) remaining in the cosolvent effluent indicating that the cosolvent could be reused for further p,p′-DDT desorption. Using this technique, between 53 and 95 pore volumes were required to reduce p,p′-DDT concentrations from 990 mg kg-1 to below Australian and New Zealand Environmental and Conservation Council (ANZECC) guidelines (50 mg kg-1). [ABSTRACT FROM AUTHOR]

A bench scale, two-phase soil washing-biosorption process was developed for the remediation of p,p′-DDT-contaminated soil (containing 990 and 7750 mg kg-1 of p,p′-DDT). Removal of p,p′-DDT from contaminated soil was achieved by washing the soil with low molecular weight primary alcohols (ethanol or 1-propanol). An improved efficiency of p,p′-DDT removal was observed with increasing C-chain length of the cosolvent and by increasing the cosolvent volume fraction. When 40 or 80% 1-propanol were used, greater than 93% of p,p′-DDT was desorbed from the respective soils. p,p′-DDT was partitioned from the cosolvent solutions using biomass of Cladosporium sp. strain AJR318,501 as the sorptive matrix. When studies were conducted using a cosolvent-recycling regime (with 80% 1-propanol) greater than 95% of p,p′-DDT was removed from Soil A (990 mg kg-1p,p′-DDT) and Soil B (7750 mg kg-1p,p′-DDT) with the majority of the desorbed organochlorine repartitioning onto the fungal biomass. Less than 2.4 μg mL-1p,p′-DDT was detected in the cosolvent wash solution of Soil A after 80 hr: potentially the cosolvent could be further reused to treat other soil. A higher concentration of p,p′-DDT was detected in the cosolvent wash solution of soil B after 120 hr (13.3 μg mL-1) indicating that the p,p′-DDT sorption sites on the fungal biomass were fully saturated. [ABSTRACT FROM AUTHOR]

A two-phase soil washing biosorption process was developed for the remediation of p,p′-DDT-contaminated soil. The process involved desorption of contaminants from soil using dilute primary alcohols (40% 1-propanol) followed by contaminant removal from cosolvent solutions using fungal biosorption. Bench scale remediation studies were preformed to simulate ex situ (recycling experiment) or in situ (soil column study) treatment strategies. Both systems were effective at cleaning the soil to below Australian regulatory p,p′-DDT levels. After 50–80 hours of soil washing, over 93% of p,p′-DDT was removed from the soil (990 mg kg-1 to <65 mg kg-1) using either of these methods. p,p′-DDT was removed from the cosolvent phase by sorption onto the fungal biomass. This resulted in only low levels of p,p′-DDT remaining in the cosolvent solution (<1.5 mg l-1). The application of both treatment strategies resulted in the rapid clean up of p,p′-DDT-contaminated soil and the potential to recycle cosolvent solutions. The ability to recycle cosolvent solutions provides a mechanism for cost reductions of the remediation strategy. [ABSTRACT FROM AUTHOR]

A simple capillary zone electrophoresis procedure was developed for the separation of arsenic species (AsO22-, AsO42-, and dimethylarsinic acid, DMA). Both counter-electroosmotic and co-electroosmotic (EOF) modes were investigated for the separation of arsenic species with direct UV detection at 185 nm using 20 mmol L-1 sodium phosphate as the electrolyte. The separation selectivity mainly depends on the separation modes and electrolyte pH. Inorganic anions (Cl-, NO2-, NO3- and SO42-) presented in real samples did not interfere with arsenic speciation in either separation mode. To improve the detection limits, sample-stacking techniques, including large-volume sample stacking (LVSS) and field-amplified sample injection (FASI), were investigated for the preconcentration of As species in co-CZE mode. Less than 1 μmol L-1 of detection limits for As species were achieved using FASI. The proposed method was demonstrated for the separation and detection of As species in water. [ABSTRACT FROM AUTHOR]

In this paper, the use of an ion-pairing reagent to improve the separation selectivity of inorganic anions in CZE was demonstrated by the addition of tetramethylammonium hydroxide (TMAOH) to the electrolyte. The separation of inorganic anions (Cl–, I–, Br–, NO2–, NO3– and SCN–) was performed using co-electroosmotic flow (EOF) with direct UV detection at 185 nm. The parameters affecting the mobility of the tested anions and the EOF such as the electrolyte pH and concentration of TMAOH in the electrolyte were examined to optimise the separation conditions. In addition, sample-stacking techniques were investigated to improve detection sensitivity. Detection sensitivities were improved 5–13-fold using electrokinetic sample stacking. The detection limits ranged from 1–3 µmol L–1. Finally, the proposed method was used for the separation of anions in groundwaters. [ABSTRACT FROM AUTHOR]

An on-column complexation method has been developed for the simultaneous determination of V(IV) and V(V). Vanadium species were chelated with aminopolycarboxylic acids to form anionic complexes which were separated by capillary zone electrophoresis (CZE) with direct UV detection. Ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentacetric acid (DTPA), nitrilotriacetic acid (NTA), and N-2-hydroxyethylethlendiaminetriacetric acid (HEDTA) were investigated as both ligand and running electrolyte. Of the ligands studied the complexes of EDTA with V(IV) and V(V) resulted in the highest selectivity and UV response. The conditions used for on-column complexation and separation, including pH, and electrolyte ligand concentration, were examined to achieve reasonable separation selectivity and detection sensitivity. The optimum separation of the anionic forms of V(IV) and V(V) was obtained by use of CZE with UV detection at 185 nm and an electrolyte containing 5 mmol L–1 EDTA at pH 4.0. Linear calibration plots were obtained in the concentration range10–300 µmol L–1; detection limits were 3 µmol L–1 for V(IV) and 1 µmol L–1 for V(V). The proposed method was demonstrated for the determination of vanadium in groundwater spiked with V(IV) and V(V). [ABSTRACT FROM AUTHOR]

Cladosporium sp. strain AJR318,501 was isolated from DDT-contaminated soil by its ability to decolourise the polymeric dye, Poly R-478. When inoculated into potato/dextrose broth containing 100 mg of DDT l−1, a 21% decrease in DDT concentration was observed 12 days after its addition, however, no transformation products were detected by gas chromatography. TLC of culture medium and mycelia extracts revealed 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane and five unknown transformation products associated with the mycelia. [ABSTRACT FROM AUTHOR]