• Resources Recycling
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• v.26 no.1
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• pp.51-58
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• 2017

The present study to develop a process for extracting nitric acid and gold from aqua regia leach solution using TBP(tributyl phosphate) was conducted. The pure aqua regia was used to investigate the extractive behavior of nitric acid depending on the concentration of extractant, concentration ratio of nitric and hydrochloric acid. The extraction rate of nitric acid and gold from the gold bearing aqua regia was also examined. The theoretical extraction number was verified by counter current using the number of operations and the phase ratio obtained from McCabe-Thiele diagram. Stripping experiments were carried out for continuous recovery of nitric acid and gold in loaded organic. Considering the effect of extraction acid and gold, the simulation showed that greater than 99.9% extraction of $103.0mg{\cdot}L^{-1}$ gold and 98.0% of $151.2g{\cdot}L^{-1}$ nitric acid could be attained in a two and three-stage counter-current extraction at an O/A phase ratio of 1:0.85. Distilled water and sodium thiosulfate were used as the nitric acid and gold stripping solution. The stripping rates were 99.5% and 92.0%, respectively. The study revealed that the recovery of nitric acid and gold from gold bearing aqua regia was a plausible approach through simultaneous extraction and continuous stripping of nitric acid and gold.

• Resources Recycling
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• v.7 no.3
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• pp.17-26
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• 1998

A study on the recovery of silver and nitric acid in the liquid waste resulted from the mediated electrochemical oxidation(MEO) process was conducted. The removal of silver in the concentrated nitric acid solutions was carried out by the electrodeposition. The removal efficiency more than 98% could be obtained in nitric acid concentrations less than 3 M with the current efficiency of nearly 100%. The experimonts on the evaporation for the recovery of nitric acid were performed as well. At the evaporation factor of 25., the degree of nitric acid recovery in 3.5 M nitric acid solution containing 0.5 to 1.0 mol% NaNO, was 80~90% resulting in 2.8~3.1 M nitric acid. The design factors and operating conditions of the distillation tower were analyzed by using MEH model derived by Maphtali-Sandholm with the throughput of 4 kg/hr for the enrichment of dilute nitric acid solution recovered by evaporation to reuse in the MEO process. The distillation column composed of eleven theoretical stages having the overall tray efficiency of 70% are needed to obtain 1.03 kg/h of 12M nitric acid and 2.97 kg/h of water with feed being introduced to the column at tray 6 from the bottom at the reflux ratio of 0.25, the reboiler with the heat load of 2.7 kW, and the condenser with the cooling load of 0.5 kW.

• Economic and Environmental Geology
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• v.52 no.6
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• pp.595-604
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• 2019

The purpose of this study was simply to obtain gold through a microwave-nitric acid experiment of invisible gold concentrate with the use of filter paper. For the purpose, this study conducted a microwave-nitric acid leaching experiment and examined nitric acid concentration. As a result of the experiment, this study discovered that Fe, Te and Ag were completely leached in the leaching solution whereas Au was not determined in all of the nitric acid conditions. The leaching solution was filtered with three filter papers and then these filter papers were analyzed with SEM/EDS. As a result of the EDS analysis, Au was detected in all of the surface and cross-section of the 1st, 2nd and 3rd filter papers. As the three filter papers containing solid-residue were analysed in the lead-fire assay, gold particles were found in all of the nitric acid conditions. In the lead-fire assay, maximum gold(452.50g/t) was recovered when nitric acid concentration was 6M and microwave leaching time was 12mins.

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.2
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• pp.233-239
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• 1998

Stimulated alveolar macrophages and neutrophils produce nitric oxide, a free radical by an inducible nitric oxide synthase(iNOS), which reacts with superoxide anion to form peroxynitrite, a more highly reactive toxic species. The objectives of the present study were to evaluate acute inflammatory lung injury and to determine iNOS mRNA induction and nitric oxide production by rat broncho-alveolar lavage cells following intratracheal treatment of silica. After 4 h exposure to silica, differential counts of broncho-alveolar lavage cells and lactate dehydrogenase(LDH) activity as well as total protein in the broncho-alveolar lavage fluid were determined. Broncho-alveolar lavage cells were also assayed for iNOS mRNA and the productions of nitrite and nitrate measured in the cells cultured. Differential analysis of broncho-alveolar lavage cells showed that the number of alveolar macrophages slightly decreased following silica treatment; however, red blood cells, lymphocytes, and neutrophils significantly were increased by 9-, 14-, and 119-fold following silica treatment, respectively, compared with the saline control. It was also found significant increases in the LDH activity and total protein in the lavage fluid obtained from silica-treated rats, indicating silica-induced acute lung injury. Northern blot analysis demonstrated that the steady state levels of iNOS mRNA in broncho-alveolar lavage cells were increased following silica treatment. The productions of nitrite and nitrate in the cultured cells were significantly increased by 2-fold following silica treatment, respectively, which were attenuated by the NOS inhibitor $N{\omega}-nitro-L-arginine-methyl$ ester(L-NAME) and partially reversed by L-arginine. These findings suggest that nitric oxide production in alveolar macrophages and recruited neutrophils is increased in response to silica. Nitric oxide may contribute in part to acute inflammatory lung injury.

• The Korean Journal of Physiology and Pharmacology
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• v.4 no.3
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• pp.263-270
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• 2000

To evaluate the involvement of nitric oxide production on the endothelium-dependent relaxation in diabetes, we have measured vascular and endothelial function and nitric oxide concentration, and the expression level of endothelial nitric oxide synthase in the streptozotocin-induced diabetic rats. Diabetic rats were induced by the injection of streptozotocin (50 mg/kg i.v.) in the Sprague-Dawley rats. Vasoconstrictor responses to norepinephrine (NE) showed that maximal contraction to norepinephrine $(10^{-5}\;M)$ was significantly enhanced in the aorta of diabetic rats. Endothelium-dependent relaxation induced by acetylcholine was markedly impaired in the aorta of diabetic rats, these responses were little improved by the pretreatment with indomethacin. However, endothelium-independent relaxation induced by nitroprusside was not altered in the diabetic rats. Plasma nitrite and nitrate $(NO_2/_3)$ levels in diabetic rats were significantly lower than in non-diabetic rats. Western blot analysis using a monoclonal antibody against endothelial cell nitric oxide synthase (eNOS) revealed that the protein level was lower in the aorta of diabetic rats than in non-diabetic rats. These data indicate that nitric oxide formation and eNOS expression is reduced in diabetes, and this would, in part, account for the impaired endothelium-dependent relaxation in the aorta of streptozotocin-induced diabetic rats.

• Journal of the Mineralogical Society of Korea
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• v.32 no.2
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• pp.113-126
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• 2019

This study aimed to effectively dissolve sulfide minerals through microwave-nitric acid leaching of invisible gold concentrate and then recover gold from the solid-residue with fire assay. For the purposes, this study conducted microwave-nitric acid leaching experiments to examine nitric acid concentration, time of microwave leaching, and sample addition effect. As results of the experiments, this study discovered that the weight loss rate of solid-residue increased as nitric acid concentration and microwave leaching time increased while weight loss rate decreased as sample addition increased. In an XRD analysis with solid-residue, it was discovered that pyrite completely disappeared when the nitric acid concentrate was 6 M and the microwave leaching time was 18 minutes. When a fire assay was carried out with solid-residue, gold particles with more content were recovered as nitric acid concentration and microwave leaching time increased whereas gold particles with more gold content were recovered as the sample addition decreased.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1995.04a
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• pp.41-44
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• 1995

• Environmental Mutagens and Carcinogens
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• v.22 no.3
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• pp.183-186
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• 2002

Hypertension is a multifactorial disease. Both genetic and environmental factors have been implicated in its etiology. Since the impairment of nitric oxide (NOS) production plays an important role in the pathogenesis of hypertension, endothelial nitric oxide synthase (ecNOS) gene is supposed to be a candidate gene of hypertension. Our study group investigated the 27 bp insertion/deletion (Ins/Del) polymorphism of ecNOS gene in 99 Korean normotensives and 98 hypertensives, respectively. There was no significant association with any cardiovascular risk factors as well as hypertension in Koreans. The Ins/Del polymorphism of the ecNOS gene indicated the similar allele distribution among ethnic groups studied. Further studies using larger sample size and subject information is required to describe the general picture of the association between the ecNOS gene polymorphic loci and hypertension

• Biomolecules & Therapeutics
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• v.18 no.4
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• pp.351-362
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• 2010

Nitric oxide (NO), synthesized from L-arginine by three isoforms of NO synthase (NOS), is a gaseous signaling molecule with an astonishingly wide range of biological and pathophysiological activities, including vasorelaxation, angiogenesis, anti-inflammation, and anti-apoptosis in mammalian cells. Recent studies have shown that NO donors and inhaled NO convert to biologically active NO under biological conditions and act as a signaling molecule in pathophysiological conditions. This review will discuss the roles of NO and its potential therapeutic implication in various human diseases, such as tumor, vascular regeneration, hypertension, wound healing, and ischemia-reperfusion injury.

• The Journal of Korean Medicine
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• v.26 no.4
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• pp.152-161
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• 2005

The excessive release of proinflammatory products by activated microglia causes neurotoxicity, and this has been implicated in the pathogenesis of neurodegenerative diseases. Harpagophytum procumbens (Pedaliaceae) has been widely used for the treatment of pain and arthritis in the clinical field. In this study, we investigated the effect of Harpagophytum procumbens against lipopolysaccharide-induced inflammation. From the present results, the aqueous extract of Harpagophytum procumbens was shown to suppress prostaglandin-E2 synthesis and nitric oxide production by inhibiting the lipopolysaccharide-stimulated enhancement of cyclooxygenase-2 and inducible nitric oxide synthase expressions in mouse BV2 microglial cells. These results suggest that Harpagophytum procumbens may offer a valuable means of therapy for the treatment of brain inflammatory diseases by attenuating lipopolysaccharide-induced prostaglandin-E2 synthesis and nitric oxide production.