• Progress in Superconductivity and Cryogenics
• /
• v.22 no.2
• /
• pp.17-20
• /
• 2020

Comprehensive utilization of tungsten tailings resources not only solves environmental problems but also creates huge economic benefits. The high content of iron impurity in tungsten tailings will have adverse effect on the downstream comprehensive utilization, whether flotation or pickling. In this paper, the Superconducting High Gradient Magnetic Separation(S-HGMS) is used to remove of Fe impurities from tungsten tailings. The optimal experimental parameters are as follows: background magnetic induction intensity is 3.0T, slurry flow velocity is 500ml/min. The Fe removal rate of Fe was 68.8% and the recovery rate was 59.53%.

• Membrane and Water Treatment
• /
• v.1 no.4
• /
• pp.273-282
• /
• 2010

Treatment and reuse of industrial wastewater is becoming a major goal due to water scarcity. This may be carried out using membrane separation technology in general and reverse osmosis (RO) in particular. In the current study, polyamide (FT-30) membrane was employed for treatment of wastewater obtained from Faraman industrial zone based in Kermanshah (Iran). The effects of operating conditions such as transmembrane pressure, cross flow velocity, temperature and time on water flux and rejection of impurities including COD by the membrane were elucidated. The aim was an improvement in membrane performance. The results indicate that most of the chemical substances are removed from the wastewater. In particular COD removal was increased from 64 to around 100% as temperature increased from 15 to $45^{\circ}C$. The complete COD removal was obtained at transmembrane pressure of 20 bars and cross flow velocity of 1.5 m/s. The treated wastewater may be reused for various applications including makeup water for cooling towers.

• Environmental Engineering Research
• /
• v.20 no.1
• /
• pp.89-97
• /
• 2015

Remediation of wastewater contaminated with metal(II)-complexed species (Cu(II)-NTA (NTA: nitrilotriacetic acid), Cu(II)-EDTA (EDTA: ethylenediamine tetraacetic acid) and Cd(II)-EDTA is attempted using the potential applicability of ferrate(VI). Kinetics of pollutant degradation is obtained with the removal of ferrate(VI) studied at wide range of pH (8.0-10.0) and the concentration of metal(II)-complexed species (0.3 to 15.0 mmol/L) employing a constant dose of ferrate(VI) i.e., 1.0 mmol/L. Pseudo-first-order and pseudo-second-order rate constants were obtained in the reduction of ferrate(VI) which was then employed to obtain the overall rate constants of the pollutant degradation. The mineralization of NTA and EDTA was obtained with the change in TOC (total organic carbon) values collected by the ferrate(VI) treated pollutant samples. Decrease in pH and molar pollutant concentrations was greatly favored the percent mineralization of NTA or EDTA by the ferrate(VI) treatment. The treated pollutant samples were filtered and subjected for AAS (atomic absorption spectrophotometric) analysis to assess the simultaneous removal of copper and cadmium from aqueous solutions at the studied pH as well at the elevated pH 12.0. Results show that an enhanced removal of cadmium or copper was achieved at pH 12.0. Overall, ferrate(VI) possesses multifunctional application in wastewater treatment as it oxidizes the degradable impurities and removes metallic impurities by coagulation process.

• Resources Recycling
• /
• v.21 no.5
• /
• pp.50-57
• /
• 2012

A comparative study has been carried out on the removal of impurities such As, Sb, Bi from the copper sulfate solution by ion exchange resin containing aminophosphosphonic acid as functional group. The various parameters which affect the removal of impurities; such as the reaction temperature, the reaction time, the amount of ion-exchange resins, the concentration of sulfuric acid in electrolyte, were studied. The basic experimental results showed that about 88% of Sb & 94% of Bi can be adsorbed in these chelate resins and removed from the copper sulfate solutions but As was removed below 10% from the solutions. And the selective elution of Bi and Sb from the adsorbed ion exchange resin also can be achieved by $H_2SO_4$ or HCl solutions. The results also showed that 98.1% of Sb and 96.6% of Bi can be adsorbed from the copper sulfate solutions after 2 Bed-volume of continuous ion exchange column test.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.11a
• /
• pp.198.1-198.1
• /
• 2010

고분자전해질 연료전지(PEMFC)의 핵심부품인 스택의 MEA는 전극과 멤브레인 전해질, GDL(Gas Diffusion Layer)로 구성되며, 전극은 Anoth극과 Cathod극으로 나뉘어 각각의 전극 특성에 적합한 전극촉매를 적용하게 된다. Anoth극과 Cathod극은 탄소 지지체 위에 원하는 사양의 희유금속이 도포되어 존재하는데 이들 희유금속은 그 희귀성으로 인해 사용 후 반드시 재사용되어야 한다. 사용된 전극에서의 희유금속 회수는 산침출, 불순물제거, 추출, 탈거 공정으로 이루어지며, 산침출 시 산화제로 사용된 NaOCl로 인한 침출용액 내의 Na+ 이온의 증가는 불순물제거 공정에 의해 반드시 제거되어야 한다. 따라서 본 연구에서는 CCG 방식으로 전극촉매를 GDL에 코팅한 MEA로부터 백금족 희유금속을 회수 시 MEA에 포함되어 있는 소량의 불순물을 제거하고자 한다.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.17 no.4
• /
• pp.429-435
• /
• 2019

Decontamination wastewater generated from the HyBRID decontamination process of the primary system in a nuclear power plant contains impurities such as sulfate ions, metal ions containing radioactive nuclides, and hydrazine (carcinogenic agent). For this reason, it is necessary to develop a technology to remove these impurities from the wastewater to a safe level. In this study, it has been conducted to remove the impurities using a decontamination wastewater surrogate, and a treatment process of the HyBRID decontamination wastewater has been established. The performance and applicability of the treatment process have been verified through 1 L scale of replicates and a pilot scale (300 L/batch) test.

• Resources Recycling
• /
• v.10 no.3
• /
• pp.51-59
• /
• 2001

Impurities removal from waste carbon black was carried out to produce high-grade carbon black. A large amount of hydrophilic carbon black is produced as a byproduct of the hydrogen production process by flame decomposition of water. Due to its impurities content such as sulphur, iron, ash, etc., it can only be used as low-grade carbon or burnt out. High-grade hydrophilic carbon black is 3~5 times more expensive than oil-based carbon black because of high production cost associated with process complexly and pollutant treatment. Hydrophilic carbon is normally used for conductive materials for batteries, pigment for plastics, electric wire covering, additives for rubber, etc. In these applications, impurity content must be blow 1 fe. In this study, magnetic separation, froth flotation and ultrasonic treatment were employed to remove impurities from the low-grade hydrophilic carbon black. Results showed that the ash, iron and sulphur content of product decreased to less than 0.01 wt.%, 0.01 wt.% and 0.3 wt % respectively and the surface area of product was about 930 $m^2$/g for conductive materials.

• Journal of the Korean Vacuum Society
• /
• v.9 no.2
• /
• pp.102-109
• /
• 2000

It is difficult to meet the cleanliness requirement of $10^{10}/\textrm{cm}^2$ for the giga level device fabrication with mechanical cleaning techniques like scrubbing which is widely used to remove the particles generated during Chemical Mechanical Polishing (CMP) processes. Therefore, the second cleaning process is needed to remove metallic contaminants which were not completely removed during the mechanical cleaning process. In this paper the experimental results for the removal of the metallic contaminants existing on the wafer surface using remote plasma $H_2$ cleaning and UV/$O_3$ cleaning techniques are reported. In the remote plasma $H_2$ cleaning the efficiency of contaminants removal increases with decreasing the plasma exposure time and increasing the rf-power. Also the optimum process conditions for the removal of K, Fe and Cu impurities which are easily found on the wafer surface after CMP processes are the plasma exposure time of 1min and the rf-power of 100 W. The surface roughness decreased by 30-50 % after remote plasma $H_2$ cleaning. On the other hand, the highest efficiency of K, Fe and Cu impurities removal was achieved for the UV exposure time of 30 sec. The removal mechanism of the metallic contaminants like K, Fe and Cu in the remote plasma $H_2$ and the UV/$O_3$ cleaning processes is as follows: the metal atoms are lifted off by $SiO^*$ when the $SiO^*$is evaporated after the chemical $SiO_2$ formed under the metal atoms reacts with $H^+ \; and\; e^-$ to form $SiO^*$.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.11 no.2
• /
• pp.85-93
• /
• 2013

This study has been carried out to elucidate the characteristics of the dissolution for Thermal Decomposed Solid Waste of uranium-bearing sludge (TDSW), the removal of impurities by an alkalization in a nitric acid dissolving solution of TDSW, and the selective removal (/recovery) of uranium by an acidification in an carbonate alkali solution, respectively. TDSW generated by thermal decomposition of U-bearing sludge which was produced in the uranium conversion plant operation, was stored in KAERI as a solid-powder type. It is found that the dissolution of TDSW is more effective in nitric acid dissolution than oxidative-dissolution with carbonate. At 1 M nitric acid solution, TDSW was undissolved about 30wt% as a solid residue, and uranium contained in TDSW was dissolved more than 99%. In order to the alkalization for the nitric acid dissolving solution of TDSW, carbonate alkalization is more effective with respect to remove the impurities. At the carbonate alkali solution controlled to about 9 of pH, Al, Ca, Fe and Zn co-dissolved with U in dissolution step was removed about $98{\pm}1%$. On the other hand, U could be recovered more than 99% by an acidification at pH about 3 in a carbonate alkali solution, which was nearly removed the impurities, adding 0.5M $H_2O_2$. It was found that uranium could be selectively recovered (/removed) from TDSW.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2005.05a
• /
• pp.56-56
• /
• 2005