• Resources Recycling
• /
• v.10 no.6
• /
• pp.22-28
• /
• 2001

A study on the recovery of yttrium was conducted using the phosphor sludges generated in the recycling process of obsolete CRTs. Yttrium was leached by HCl and $HNO _3$. The leaching efficiency of yttrium was extensively investigated in terms of acid concentration, leaching temperature and time, and pulp density. Yttrium and lead was recovered from leaching solutions also by precipitation method. The leaching behavior of yttrium was similar in both acids. The leaching efficiency of yttrium for both acids increased with time at the conditions of 3.0M, $90^{\circ}C$, and 280 g/L of pulp density. After 40 minutes, it was saturated to 93% and 90% for HCl and HNO$_3$respectively. Yttrium was recovered from leaching acid solution by the addition of $H_2$$C_2$$O_4$while lead was removed as $PbSO_4$by $Na_2$ $SO_4$.

• Resources Recycling
• /
• v.10 no.6
• /
• pp.9-14
• /
• 2001

A sulfuric acid leaching of $LiCoO_2$as cathodic active materials of lithium ion secondary batteries was investigated in terms of reaction variables. In the absence of a reducing agent, the extraction of cobalt was less than 40% in 2 M sulfuric acid at $75^{\circ}C$ instead of that of lithium could be almost 100% in the same conditions. To improve the Co extraction, hydrogen peroxide was used as a reducing agent in the range 2~20 vol%. When over 10vo1% hydrogen peroxide was added, the extractions of both metals were improved to about 95%. It seems to be due to the reduction of Co(III) to Co(II) that can be readily dissolved. The extractions of Co and Li were increased with increasing $H_2$$SO_4$concentration and temperature, and amount of hydrogen peroxide and with decreasing of pulp density. The optimum leaching conditions were determined at $2 M H_2$$SO_4$concentration, $75^{\circ}C$ operating temperature, 100 g/L. initial pulp density, 20 vol% $H_2$$O_2$addition and 30 min.

• Resources Recycling
• /
• v.15 no.6 s.74
• /
• pp.10-15
• /
• 2006

As a basic study on recovery of valuable metals such as vanadium and nickel from metal oxide obtained from waste orimulsion ash, we conducted selectively leaching of vanadium and nickel using $Na_2CO_3$ leaching and ammoniacal leaching, respectively. The 97% of vanadium was selectively leached at an optimum experimental condition, 50g/L $Na_2CO_3$, pulp density 50g/L, and 35% $H_2O_2$ 50ml/L, $25^{\circ}C$... for 1 hr, whereas no nickel was leached. In ammoniacal leaching study, 95% of nickel was selectively leached at the optimal experimental condition, $NH_4OH\;2M,\;(NH_4){_2}SO_4$ 1.5M, pulp density 50g/L, 25, for 4 hr along with 3% of vanadium.

• Resources Recycling
• /
• v.20 no.4
• /
• pp.65-70
• /
• 2011

Environmental friendly leaching process for the recovery of cobalt and lithium from the $LiCoO_2$ was investigated by organic acids as a leaching reagent. The experimental parameters, such as organic acid type, concentrations of leachant and hydrogen peroxide, reaction time and temperature as well as the pulp density were tested to obtain the most effective conditions for the leaching of cobalt and lithium. The results showed that the latic acid was the most effective leaching reagent for cobalt and lithium among the organic acids and was reached about 99.9% of leaching percentage respectively. With the increase of the concentration of citric acid, hydrogen peroxide and temperature, the leaching rate of cobalt and lithium increased. But the increase of pulp density decreased the leaching rate of cobalt and lithium.

• Resources Recycling
• /
• v.31 no.5
• /
• pp.26-33
• /
• 2022

Molybdenum is widely used in many materials; thus, its recovery from ores and secondary resources has attracted considerable attention. In this study, the leaching of molybdenite ore using hydrochloric acid containing sodium chlorate as an oxidizing agent was studied. The effects of several variables, such as the concentrations of HCl and NaClO₃, reaction temperature and time, and pulp density, on the leaching of the ore were investigated. Under strong acidic and oxidizing conditions, the sulfide in the ore was dissolved as a sulfate ion, which formed gypsum with Ca(II), leading to a decrease in the leaching percentage of Mo(VI) from the ore. The leaching percentage of molybdenum was greater than 90%, while those of iron, calcium, and silicon were 38, 29, and 67%, respectively, under the optimum conditions: 2.0 M HCl, 0.5 M NaClO₃, pulp density of 5 g/L, temperature of 90 ℃, and treatment time of 60 min.

• The korean journal of orthodontics
• /
• v.28 no.3 s.68
• /
• pp.419-429
• /
• 1998

This study was carried out in order to study early histologic changes and repair reaction appling to extrusive force for 3rd premolar of adult dogs. After 1 week of extrusive force with elastic chain, one of dogs was sacrified and after 3 weeks retention period, another dog was sacrified. The paraffin sections of samples were stained with Hematoxylin - Eosin and Masson's Trichrome and were examed by light microscopy . The obtained results as follows 1. In Hematoxylin - Eosin and Masson Trichrome stain of control group , the periodontal ligament width was constant from apical third to cervical third of the root and periodontal fiber arrangement was horizontal or oblique in cervical third. oblique in middle third, oblique in apical third of root. in alveolar bone, smooth appearance was shown 2. In Group 1, all periodontal fiber arrangement was oblique toward tooth, and the periodontal ligament width increased Partially PDL was ruptured in apex. In MT stain, immature bone formation was seen at alveolar crest area. Active bone formation was observed along the one side of alveolus, and apical portion of pulp was involved with blood vessel rupture , vacuolization of pulp tissue and hyperemia 3. In Group 2, most periodontal ligament arrangement and PDL width was repaired and fiber density increased. In MT stain, mineralization of immature bone on the alveolar crest was progressed. In pulp, vacuole and hyperemia was diminished and fibrotic change was diminished 4. After 3 week periodontal ligament has more repair ability than pulp tissue. pulp was involved with vacuolization and fibrosis, so it takes more time for repair.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.24 no.1
• /
• pp.301-312
• /
• 1997

The purpose of this study was to evaluate the analgesic effect on pulp induced by pulsed Nd : YAG laser according to the power density, irradiated time and the method of application (Non-contact vs contact) in vivo. Experiments were carried out on 90 volunteers who have sound 4 canines. Each canine was grouped by the intensity and the time of irradiation of pulsed Nd : YAG laser was measured. Mean EPT response(units) was measured at 5 min, 30 min, and 60 min after irradiation with various intensity(1.5-3W, 15-30Hz), irradiated time (1.5min, 3min), and application method (Non-contact and contact). The results were as follows: 1. 5 minutes after irradiation, the mean EPT response(units) was increased by 32 % in the non-contact method and by 35% in the contact method of application. Which showed significant difference in mean EPT response(units) compared to not-lased canine in each groups(P<0.05). 2. The mean EPT response(units) with irradiating condition according to the various laser intensity, and the irradiation time stastically did not show significant difference in each groups as time elapsed. 3. There was no significant difference between the non-contact and contact method in the mean EPT response(units). 4. The mean EPT response(units) returned to the baseline value within 30 miuntes. In regard to the above results, the analgesic effect on pulp induced by pulsed Nd : YAG laser resulted a slight increase of pulpal pain threshold, but it was not as high as to replace the role of drug analgesia as whole. This technique can be used for inducing pulpal analgesia as adjunct to other pain control methods and is needed to develop better analgesic effects.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.25 no.3
• /
• pp.583-597
• /
• 1998

The purpose of this study was to evaluate temperature change occurred in enamel, dentin and pulp due to the heat from cavity prepration with laser. We made three models had different cavity depth: cavity depth of model A was 3.52mm, model B was 2.32mm, model C was 1.16mm. We irradiated cavity base with thermal capacity of $30J,100J,300J/cm^2s$ during few seconds and studied the change of temperature in tooth during 10 seconds, and estimated change of thermal capacity by different irradiated site and exposure time. At $300J/cm^2$ irradiation for 2 seconds, the temperature of irradiated surface was elevated fast according to irradiated thermal energy during 1 second. In proportion to continuous exposure time, temperature elevated slowly. The surface temperature was $1370^{\circ}C$. After discontinue of thermal irradiation, the heat of irradiated surface was diffused in dentin and pulp and the greatest temperature was made. The greatest temperature was disappeared within 10 seconds The greatest temperature of the inner part of model brought about very severe change by different depth. Temperature in pulp was raised by the greater irradiated energy density and exposure time.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.46 no.5
• /
• pp.9-18
• /
• 2014

London Convention on the prevention of marine pollution by dumping of wastes and other matter prohibits the deliberate disposal of paper mill sludges at sea. In order to explore the alternative plan on the prohibition of sludge disposal at sea, the biodegradable seedling pot was developed by mixing the sludge with old newspaper (ONP) in appropriate mixing ratios. The C/N ratio of the mixed sludge was below 20, leading to rapid deterioration of the organic matters composing the seedling pot. The increased ONP contents in the seedling pot resulted in the increase of pot thickness and thereafter in the decrease of pot density. Cellulose fibers in ONP promoted water absorption of the pot but AKD addition helped the seedling pot to repel water during raising seedling. Breaking length and burst strength of the seedling pot were improved by addition of wet strength additives but air permeability was a little diminished. Biodegradable rate of the seedling pot in a soil was accelerated by the attack of soil microbes at the beginning, and finally the pot was completely degraded in 150 days in a soil.

• Imaging Science in Dentistry
• /
• v.54 no.3
• /
• pp.276-282
• /
• 2024

Purpose: This study aimed to assess the performance of 2-dimensional (2D) imaging with microscopy coils in delineating teeth and periodontal tissues compared with conventional 3-dimensional(3D) imaging on a 3 T magnetic resonance imaging (MRI) unit. Materials and Methods: Twelve healthy participants (4 men and 8 women; mean age: 25.6 years; range: 20-52 years) with no dental symptoms were included. The left mandibular first molars and surrounding periodontal tissues were examined using the following 2 sequences: 2D proton density-weighted (PDw) images and 3D enhanced T1 high-resolution isotropic volume excitation (eTHRIVE) images. Two-dimensional MRI images were taken using a 3 T MRI unit and a 47 mm microscopy coil, while 3D MRI imaging used a 3 T MRI unit and head-neck coil. Oral radiologists assessed dental and periodontal structures using a 4-point Likert scale. Inter- and intra-observer agreement was determined using the weighted kappa coefficient. The Wilcoxon signed-rank test was used to compare 2D-PDw and 3D-eTHRIVE images. Results: Qualitative analysis showed significantly better visualization scores for 2D-PDw imaging than for 3D-eTHRIVE imaging (Wilcoxon signed-rank test). 2D-PDw images provided improved visibility of the tooth, root dental pulp, periodontal ligament, lamina dura, coronal dental pulp, gingiva, and nutrient tract. Inter-observer reliability ranged from moderate agreement to almost perfect agreement, and intra-observer agreement was in a similar range. Conclusion: Two-dimensional-PDw images acquired using a 3 T MRI unit and microscopy coil effectively visualized nearly all aspects of teeth and periodontal tissues.