• Journal of Korean Society of Water and Wastewater
• /
• v.26 no.3
• /
• pp.453-461
• /
• 2012

The degradation characteristics of TCE by Ferrate(VI) oxidation have been studied. Ferrate(VI) were prepared by electrochemical method. The degradation efficiency of TCE in aqueous solution was investigated at various pH values, Ferrate(VI) doses and aqueous solution temperature values. GC-ECD was used to analyze TCE. TCE was degraded rapidly by ferrate(VI) in aqueous solution, Also, the experimental results showed that TCE removal efficiency increased with the increase of Ferrate(VI) doses. The effect of pH was investigated and the maximum degradation efficiency was obtained at pH 7. And intermediate products were identified by GC-MS techniques. Ethyl Chloride, Dichloroethylene, Chloroform, 1,1-dichloropropene, Trichloroacetic acid and Trichloroethane were identified as a reaction intermediate, and $Cl^-$ was identified as an end product.

• Journal of Korean Society of Water and Wastewater
• /
• v.25 no.5
• /
• pp.643-649
• /
• 2011

Degradation of benzothiophene(BT) in the aqueous phase by potassium ferrate(VI) was investigated. Potassium ferrate(VI) was prepared by the wet oxidation method. The degradation efficiency of BT was measured at various values of pH, ferrate(VI) dosage and initial concentration of BT. BT was degraded rapidly within 30 seconds by ferrate(VI). While the highest degradation efficiency was achieved at pH 5, the lowest degradation efficiency was achieved at pH 9. Also, the initial rate constant of BT increased with decreasing of the BT initial concentration. In addition, the intermediate analysis for the reaction of BT and ferrate(VI) has been conducted using GC-MS. Benzene, styrene, benzaldehyde, formaldehyde, benzoic acid, formic acid, and acetic acid were identified as reaction intermediates, and ${SO_4}^{2-}$ was identified as an end product.

• Advances in environmental research
• /
• v.1 no.2
• /
• pp.167-179
• /
• 2012

Pistachio shell (Pistacia vera) (PS), a low-cost material, has been utilized for the removal of the Cr(VI) ions after treatment with citric acid. Batch experimental steps were applied to obtain Cr(VI) ion adsorption details for the equilibrium between Cr(VI) and modified pistachio shell (MPS). The influences of contact time, pH, adsorbent dose and initial chromium concentration on the adsorption performance of MPS was investigated in detail. The results displayed that adsorption of Cr(VI) by MPS reached to equilibrium after 2 h and after that a little change of Cr(VI) removal efficiency was observed. The sorption percent is higher at lower pH and lower chromium concentration. Two possible mechanisms for reduction of Cr(VI) to Cr(III) can be suggested in Cr(VI) removal. In the first mechanism, Cr(VI) is reduced to Cr(III) by surface electron-donor groups of the adsorbent and the reduced Cr(III) forms complexes with adsorbent or remains in the solution. This Cr(III) is not adsorbed by adsorbent at pH 1.8. But in second mechanism, the adsorption-coupled reduction of Cr(VI) to Cr(III) occurred on the adsorbent sites. The equilibrium sorption capacity of Cr(VI) ion after 2 h was 64.35 mg/g for MPS.

• Journal of Korean Society of Water and Wastewater
• /
• v.35 no.1
• /
• pp.27-37
• /
• 2021

Tetracycline is one of the most commonly used as antibiotics for the livestock industry and it is still widely used nowadays. Tetracycline and its metabolites are excreted with excrement, which is difficult to completely removed with conventional sewage treatment, therefore it is apprehended that the tetracycline-resistant bacteria occurs. In this study, the oxidant named ferrate(VI) was used to degrade the tetracycline and investigate the reaction between ferrate(VI) and tetracycline under various aqueous conditions. The highest degradation efficiency of tetracycline occurred in basic condition (pH 10.1 ± 0.1) because of the pKa values of tetracycline and ferrate(VI). The results also showed the effect of water temperature on the degradation of tetracycline was not significant. In addition, the dosage of ferrate(VI) was higher, the degradation of tetracycline and the self-degradation of ferrate(VI) also higher, finally the efficiency of ferrate(VI) was lower. The results said that the various mechanisms effects the reaction of ferrate(VI) oxidation, it required the consideration of the characteristics of the target compound for optimal degradation efficiency. Additionally, intermediate products were detected with LC/MS/MS and three degradation pathways were proposed.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.2 no.2
• /
• pp.135-143
• /
• 2004

An experimental study on the sorption of U(VI) onto a Korean granite was performed as a function of the geochemical parameters such as contact time, pH, ionic strength, and carbonate concentration using a batch procedure. The distribution coefficient,$K_d$, was about 1-200 mL/g depending on the experimental conditions. The sorption of U(VI) onto granite particles was greatly dependent upon the contact time, pH, and carbonate concentration, but insignificantly dependent on the ionic strength. It was noticed that the sorption of U(VI) onto granite particles was highly correlated with the uranium speciation in the solution, which was dependent on the pH and carbonate concentrations. It was deduced from the kinetic sorption experiment that a two-step first-order kinetic behavior could dominate the kinetic sorption of U(VI) onto granite particles. In the alkaline range of a pH above 7, U(VI) sorption was greatly decreased and this might be due to the formation of anionic U(VI)-carbonate aqueous complexes as predicted by the speciation calculations.

• Carbon letters
• /
• v.7 no.3
• /
• pp.171-179
• /
• 2006

A carbonaceous sorbent was prepared from rice husk via sulphuric acid treatment. After preparation and washing, the wet carbon with moisture content 85% was used in its wet status in this study due to its higher reactivity towards Cr(VI) than the dry carbon. The interaction of Cr(VI) and the carbon was studied and two processes were investigated in terms of kinetics and equilibrium namely Cr(VI) removal and chromium sorption. Cr(VI) removal and chromium sorption were studied at various initial pH (1.6-7), for initial Cr(VI) concentration (100 mg/l). At equilibrium, maximum Cr(VI) removal occurred at low initial pH (1.6-2) where, Cr(III) was the only available chromium species in solution. Cr(VI) removal, at such low pH, was related to the reduction to Cr(III). Maximum chromium sorption (60.5 mg/g) occurred at initial pH 2.8 and a rise in the final pH was recorded for all initial pH studied. For the kinetic experiments, approximate equilibrium was reached in 60-100 hr. Cr(VI) removal data, at initial pH 1.6-2.4, fit well pseudo first order model but did not fit pseudo second order model. At initial pH 2.6-7, Cr(VI) removal data did not fit, anymore, pseudo first order model, but fit well pseudo second order model instead. The change in the order of Cr(VI) removal process takes place in the pH range 2.4-2.6 under the experimental conditions. Other two models were tested for the kinetics of chromium sorption with the data fitting well pseudo second order model in the whole range of pH. An increase in cation exchange capacity, sorbent acidity and base neutralization capacity was recorded for the carbon sorbent after the interaction with acidified Cr(VI) indicating the oxidation processes on the carbon surface accompanying Cr(VI) reduction.

• Journal of Sericultural and Entomological Science
• /
• v.38 no.1
• /
• pp.25-30
• /
• 1996

The adsorption mechanism of Chromium(VI) uptake in silk fibroin fibers was discussed. The adsorption equilbrium of Chromium(VI) is significantly influenced by the initial adsorption rate and it showed 52% of the equilibrium uptake. The Chromium(VI) uptake by silk fibroin in increased with the acidic range of pH, which react upon Chromium(VI) oxidations. The enthalpy change in the Chromium(VI) on the temperatures, $\Delta$H, was found to be 39.7 KJ.mol-1, It means that the Chromium(VI) adsorption proceeds via a certain complex chemical reaction and the Chromium complex was found to be coordinated with carbonyl group of amides from the result of infrared spectra. The chroming of silk fibroin fibers in moderated in the conditions of 5$0^{\circ}C$, pH 2.4, and 3 hours, which prevent from the loss of physical properties. The equilibrium adsorption is attained at 5 X 10-3M of Chromium(VI) solutions.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.11
• /
• pp.6039-6046
• /
• 2013

Cr(VI)-heterocyclic complex[Cr(VI)-2-methylpyrazine] was synthesized by the reaction between of heterocyclic compound(2-methylpyrazine) and chromium trioxide, and characterized by IR and ICP analysis. The oxidation of benzyl alcohol using Cr(VI)-2-methylpyrazine in various solvents showed that the reactivity increased with the increase of the dielectric constant(${\varepsilon}$), in the order : cyclohexene${\rho}$) was Cr(VI)-2-methylpyrazine= -0.65(308K). The observed experimental data have been ratiolized. The hydride ion transfer causes the prior formation of a chromate ester in the rate-determining step.

• Proceedings of the Ginseng society Conference
• /
• 2002.10a
• /
• pp.351-365
• /
• 2002

Earlier studies have demonstrated that chromium (Cr) VI compounds have been shown to be more toxic and carcinogenic than other chromium compounds. The aim of the present work was to evaluate the antioxidant effects of red ginseng against chromium VI -induced toxicity and free radical generation. Sixty adult male rats were divided into six equal groups include: control group, group received Cr VI alone (50 mg/kg b.w.), group treated with Korean ginseng (K. ginseng) alone (20 mg/kg b.w), group treated with Cr VI for 15 days then received K. ginseng for other 15 days, group treated with Cr VI and K. ginseng at the same time for 15 days, and group treated with K. ginseng for 15 days then Cr VI for other 15 days. The results revealed that Cr VI caused significant increase in ALT, AST, ALP, G-GT, urea, creatinine, and acid phosphatase. Whereas, it caused significant decrease in TP, albumin, testosterone, GPX, and SOD indicating a stress for liver, kidney and testes. K. ginseng alone caused significant increase in GPX and SOD activities in healthy animals and this result suggests a prophylactic role for this herb in protection against the damaging impact induced by free radical species. Furthermore, the other biochemical parameters measured after K. ginseng administration were comparable to the control values. Treatment with Cr VI followed by K. ginseng, Cr VI and K. ginseng or K. ginseng followed by Cr VI resulted in significant improvement in all tested parameters towards the normal values of the controls. However, this improvement was pronounced in the group pre-treated with K. ginseng for 15 days before Cr VI administration. It could be concluded that K. ginseng exhibited a protective action against the toxic effects of Cr VI and it had the ability to scavenge free radicals resulted from Cr VI intoxication.

• Journal of Korea Soil Environment Society
• /
• v.4 no.2
• /
• pp.11-31
• /
• 1999

Removal of hexavalent chromium from artificial groundwater (AGW) by granular activated carbon (GAC) was investigated in batch and continuous-flow column studies. Experimental parameters that were examined included solution pH, presence of dissolved oxygen (DO), and GAC pretreatment with Fe(II). As the solution pH increased from 4 to 7.5, the amount of Cr(VI) removed by both GACs decreased significantly. Exclusion of DO from the experimental systems resulted in greater removal of Cr(VI) from solution, possibly as a result of reduction to Cr(III). However, pretreatment of the GAC with a reductant (Fe(II)) did not improve Cr(VI) removal. Equilibration With 0.01 M $K_2$$HPO_4$[to extract adsorbed Cr(VI)] followed by a wash with 0.02 N $K_2$$HPO_4$[to remove precipitated/sorbed Cr(III)] proved to be a viable approach for the regeneration of carbons whose Cr(VI) removal capacities had been exhausted. The performance of the regenerated carbons exceeded that of the virgin carbons, primarily because of the favorable adsorption of Cr(VI) at lower pH values and the reduction of Cr(VI) to Cr(III), The presence of Cr(III) in acid wash solutions provides direct evidence that Cr(VI) is reduced to Cr(III) in GAC systems under relatively acidic conditions. GAC performance over five complete cycles was consistently high, which suggests that such a system will be able to function over many operation cycles without deleterious effects.