• Resources Recycling
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• v.31 no.1
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• pp.65-77
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• 2022

A study was conducted in Korea on the leaching behavior and possibility of recovery of vanadium and other valuable metals from domestic vanadium titanomagnetite (VTM) by direct acid leaching. In this study, a VTM concentrate containing 0.8% V₂O₅ was used, and the ratio of magnetite to ilmenite was calculated as 1.9:1 by using the HSC program. The leaching behavior of vanadium from the VTM was similar to that of iron, and it was affected by the concentration of sulfuric acid and temperature. Further, titanium could be leached in the form of TiOSO₄ at a temperature higher than 75℃. To improve the leaching efficiency of V, Fe, and Ti in VTM, reductive sulfuric acid and oxidative sulfuric acid leaching were performed. When Na₂SO₃ was used as a reducing agent, the leaching rate of vanadium was 80% of that in that case of leaching by sulfuric acid. Similarly, the leaching rate of titanium increased from 20% to 50%. When Na₂S₂O₈ was used as an oxidation agent, most of the vanadium was leached, and the main residue found by XRD analysis was ilmenite. In studies on the possibility of recovering valuable metals, the selective extraction of metals is hardly achieved by solvent extraction from oxidation leaching solutions; however, in this study, Cyanex 923, a solvation extractant from reductive leaching solutions, could selectively extract Ti.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.1
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• pp.52-58
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• 2015

White ledger usually includes white office paper, computer paper, and copy machine paper. Because these grades need high optical properties, fluorescent whitening agents (FWAs) are widely used in the papermaking process. FWAs are the most powerful and effective chemical used to obtain high CIE whiteness and ISO brightness in papers. The rising demand for white or ultra-white papers has increased the use of FWAs. However, FWAs used in white ledger can restrict its use, even though white ledger is widely used as a raw material in paperboard mills. Therefore, it is necessary to develop methods to control FWAs from white ledger to increase its use in paperboard mills. In this study, the behaviors of disulpho fluorescent whitening agent (D-FWA), tetrasulpo fluorescent whitening agent (T-FWA), and hexasulpho fluorescent whitening agent (H-FWA) during the recycling process were identified as a first step to remove FWAs from white ledger. We prepared four types of papers (dyed with D-FWA, T-FWA, and H-FWA), disintegrated these papers, and made handsheets. This recycling process was carried out three times in a laboratory. After each round of recycling, the hand-sheets' CIE whiteness and fluorescence index were measured, and the distribution of FWAs in the Z-direction was observed using CLSM images. FWA reductions in the model papers were calculated using fluorescence indices as a function of the number of recycling. FWAs in handsheets containing T-FWA and H-FWA decreased linearly as a function of the number of recycling, but D-FWA did not show a significant reduction in the fluorescence index after recycling. T-FWA and H-FWA showed similar distributions of D-FWA after recycling. Therefore, as much T-FWA and H-FWA as possible must be detached in the early processes of papermaking at paperboard mills.

• Resources Recycling
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• v.21 no.5
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• pp.58-64
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• 2012

Ti button type ingots were prepared by recycling of Ti turning scraps using vacuum arc melting process for production of consumable arc electrode. The behavior of impurities such as Fe, W, O, and N in the Ti button ingots was investigated and the properties of the Ti button ingots were also evaluated. In the case of oxygen gaseous impurity, the oxygen layers on the surface of the Ti turning scraps were easily removed by the first vacuum arc melting. On the other hand, the solute oxygen in the Ti turning scraps was not removed by the next melting. In the case of Fe, major impurity in the Ti turning scraps, the removal degree in the final Ti button ingot refined by vacuum arc melting for 20 minutes was approximately 43 %, which is due to the vapor pressure difference between Ti and Fe. As a result, the Ti button ingots with ASTM grade 3 could be obtained by multiple vacuum arc melting from the Ti turning scraps. Therefore, it was confirmed that the preparation of consumable electrode for vacuum arc remelting could be possible by recycling of Ti turning scraps.

• Resources Recycling
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• v.10 no.6
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• pp.22-28
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• 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
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• v.14 no.5 s.67
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• pp.32-39
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• 2005

Leaching behavior of nickel contained in waste Multi-Layer Ceramic Capacitor (MLCC) was investigated using a batch reactor. The effects of acid type, acid concentration, leaching temperature, particle size, and reaction time on the extraction of nickel metal from waste MLCC were examined. As a result, 97% of nickel contained in waste MLCC was leached out in 30 min at the temperature of $90^{\circ}C$ under the condition of $HNO_3$ concentration 1N, solid/liquid ratio 5 g/L and particle size $-300/+180{\mu}m$. It was also found that a Jander equation was useful to fit well the leaching rate data. The rate of nickel leaching is controlled by pore diffusion in $BaTiO_3$ layer and has an activation energy of 37.6 kJ/mol (9.0 kcal/mol).

• Resources Recycling
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• v.9 no.6
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• pp.15-22
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• 2000

There are many intensive efforts to develop the recycling technologies of waste plastics in steel works to tackle the saving of resources and the protection of the natural environment. In this study, the thermogravimetric analyses for three kinds of plastics, the combustion experiments and the theoretical approach for calculating the flame temperature in the blast furnace had been performed to understand the behavior of plastics in the raceway. The thermal decompositions of plastics were studied using thermogravimetric analyzer under the atmospheric condition. The starting temperature of thermal decomposition and the maximum weight loss point were increased in proportion to the logarithmic values of heating rate. The combustion characteristics of plastics were simulated in a coke-bed combustor. The combustion efficiency of plastics was lower than that of pulverized coal. The oxygen enrichment was found out to be one of the useful methods to increase the combustibility of plastics in raceway. The maximum injection rate of plastics was calculated based on the flame temperature.

• Resources Recycling
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• v.22 no.4
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• pp.62-69
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• 2013

A study on the recovery of lithium and leaching behavior of NCM powder by carbon reduction for NCM-system Li-ion battery scraps was conducted. First of all, the oxide powders of NCM-system with layer structure were decomposed by carbon, lithium was converted to lithium carbonate by carbon reaction at above $600^{\circ}C$. The lithium carbonate powders with 99% purity were manufactured by washing method with water and concentration process for NCM powder after carbon reduction. The reaction yield was approximately 88% at $800^{\circ}C$ by carbon reduction. At this time, leaching efficiency at 2M sulfuric acid concentration was over 99% for cobalt, nickel and manganese.

• Resources Recycling
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• v.31 no.6
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• pp.18-24
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• 2022

Dry reduction using natural gas was proposed to recover tin from waste tin oxide generated in a tin bath that was used for controlling the smoothness of architectural glass during production, and the reduction behavior was investigated. The utilized vertical natural gas dry reduction system is capable to process 4 L or 20 kg depending on input raw materials. The system was established by applying the upper intake and lower discharge method. The recovery rate was 97.2% at 800 ℃ and 4 sccm flow rate and increased with the amount of input gas. Hydrogen accounted for 23% of the discharge gas, showing a 16.6% hydrogen conversion rate. The reaction behavior of tin recovered via natural gas reduction provides basic data on the new waste resource reduction/recovery technology.

• Resources Recycling
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• v.19 no.5
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• pp.3-12
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• 2010

Platinum group metals with high purity are important raw materials for high technology industry. Since there are no domestic ores containing PGMs, it is of importance to develop a separation process by which ultra pure PGMs can be recovered from diverse spent resources. Data on the chemical properties and dissolution behavior of PGMs were obtained from the literature. A method for the thermodynamic analysis of the HCl solution with chlorine gas was introduced. Utilizing the difference in the chemical properties and dissolution behavior of PGMs would lead to an efficient separation process to recover ultra pure PGMs.

• Resources Recycling
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• v.27 no.3
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• pp.78-85
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• 2018

Effect of ball milling treatment on the hydrochloric acid leaching performance of black dross was investigated to recover alumina. Ball milling time and speed showed limited effect on the leaching behavior of the alumina in the mechanically dross. Under the optimum mechanical activation condition (for 1h at 700 rpm), the leaching of alumina in hydrochloric acid solution was significantly affected by leaching time and reaction temperature. MgO was completely dissolved in most of the leaching conditions, while a small amount of Ca, Fe, Si and Ti oxides was dissolved. Although 80% of alumina was dissolved, the dissolved minor components such as Ca, Fe, Mg, Si and Ti oxides should be separated to recover pure alumina solution.