Cobalt (Co) is mainly used to prepare cathode materials for lithium-ion batteries (LIBs) and binder metals for WC-Co hard metals. Developing an effective method for recovering Co from WC-Co waste sludge is of immense significance. In this study, Co is extracted from waste cemented carbide soft scrap via mechanochemical milling. The leaching ratio of Co reaches approximately 93%, and the leached solution, from which impurities except nickel are removed by pH titration, exhibits a purity of approximately 97%. The titrated aqueous Co salts are precipitated using oxalic acid and hydroxide precipitation, and the effects of the precipitating agent (oxalic acid and hydroxide) on the cobalt microstructure are investigated. It is confirmed that the type of Co compound and the crystal growth direction change according to the precipitation method, both of which affect the microstructure of the cobalt powders. This novel mechanochemical process is of significant importance for the recovery of Co from waste WC-Co hard metal. The recycled Co can be applied as a cemented carbide binder or a cathode material for lithium secondary batteries.

This study focuses on the fabrication of a WC/Co composite powder from the oxide of WC/Co hardmetal scrap using solid carbon in a hydrogen gas atmosphere for the recycling of WC/Co hardmetal. Mixed powders are manufactured by mechanically milling the oxide powder of WC-13 wt% Co hardmetal scrap and carbon black with varying powder/ball weight ratios. The oxide powder of WC-13 wt% Co hardmetal scrap consists of WO3 and CoWO4. The mixed powder mechanically milled at a lower powder/ball weight ratio (high mechanical milling energy) has a more rapid carbothermal reduction reaction in the formation of WC and Co phases compared with that mechanically milled at a higher powder/ball weight ratio (lower mechanical milling energy). The WC/Co composite powder is fabricated at 900℃ for 6 h from the oxide of WC/Co hardmetal scrap using solid carbon in a hydrogen gas atmosphere. The fabricated WC/Co composite powder has a particle size of approximately 0.25-0.5 μm.

This study is carried out to obtain basic data regarding oxidation and reduction reactions, originated on the recycling of waste tungsten hard scraps by oxidation and reduction processes. First, it is estimated that the theoretical Gibbs free energy for the formation reaction of WO2 and WO3 are calculated as ΔG1,000K= -407.335 kJ/mol and ΔG1,000K = -585.679 kJ/mol, from the thermodynamics data reported by Ihsan Barin. In the experiments, the oxidation of pure tungsten rod by oxygen is carried out over a temperature range of 700-1,000oC for 1 h, and it is possible to conclude that the oxidation reaction can be represented by a relatively linear relationship. Second, the reduction of WO2 and WO3 powder by hydrogen is also calculated from the same thermodynamics data, and it can be found that it was difficult for the reduction reaction to occur at 1,027oC, in the case of WO2, but it can happen for temperatures higher than 1127oC. On the other hand, WO3 reduction reaction occurs at the relatively low temperature of 827oC. Based on these results, the reduction experiments are carried out at a temperature range of 500-1,000oC for 15 min to 4 h, in the case of WO3 powder, and it is possible to conclude that the reduction at 900oC for 2h is needed for a perfect reduction reaction.

It should be noted that the use of the lathe scrap for making fiber reinforced cementitious composites(FRCCs) raised friendly environmental effect as well as economy because the lathe scrap is a by-product of steel manufactures and is occurred when lathe and milling works of them are conducted to process steel manufactures. Thus, the purpose of this research is to investigate the effect of measurements of lathe scrap on the characteristics of FRCCs. For this purpose, various lathe scraps were collected from processing plants of metal, and then these were processed 10mm, 20mm, and 40mm in lengths for 2mm and 4mm in widths, respectively. FRCCs containing lathe scraps were made according to their widths and lengths, and then characteristics such as the workability, compressive strength, and flexural strength of those were evaluated. As a result, it was observed from the test results that the optimum measurements of the lathe scrap for manufacturing FRCCs was 2mm in width and 40mm in length.

폐 PCBs의 스크랩으로부터 염소-차아염소산염 용액을 이용하여 Au와 Ag를 친환경적이고 효과적으로 용출시키고자 하였다. PCBs에 Cu, Sn, Sb, Al, Ni, Pb, Au 등과 같은 유용금속이 함유되어 있는 것을 EDS 분석으로 확인하였다. 최대 Au 용출율은 1%의 광액농도, 2:1의 염산:차아염소산나트륨 그리고 2 M의 NaCl 농도조건이다. Au 회수율이 가장 높은 메타중아황산나트륨 농도는 3 M에서였다. 염소-차아염소산염이 폐 컴퓨터에 함유되어 있는 Au와 Ag를 효과적으로 용출시킬 수 있는 용매제 임을 그리고 메타중아황산나트륨이 Au를 간단하게 침전시킬 수 있는 첨가제임을 확인하였다.

Cathode materials and their precursors are prepared with transition metal solutions recycled from the thewaste lithium-ion batteries containing NCM (nickel-cobalt-manganese) cathodes by a H2 and C-reduction process. Therecycled transition metal sulfate solutions are used in a co-precipitation process in a CSTR reactor to obtain the tran-sition metal hydroxide. The NCM cathode materials (Ni:Mn:Co=5:3:2) are prepared from the transition metal hydroxideby calcining with lithium carbonate. X-ray diffraction and scanning electron microscopy analyses show that the cathodematerial has a layered structure and particle size of about 10 µm. The cathode materials also exhibited a capacity ofabout 160 mAh/g with a retention rate of 93~96% after 100 cycles.

With an increased production of Printed Circuit Boards (PCBs) in electronic equipment, the consumption of solder alloys is growing globally. Recently, increasing importance of recycling solder scrap has been recognized. Generally, solder scrap contains many impurities such as plastics and other metals. Hazardous components must be eliminated for recycling solder scrap. The present work studied pretreatment for reuse of solder scrap alloys. An experiment was conducted to enhance the cleanliness of solder scrap melt and eliminate impurities, especially lead. Physical separation with sieving and magnetic force was made along with pyrometallurgical methods. A small decrease in lead concentration was found by high temperature treatment of solder scrap melt. The impurities were removed by filtration of the solder scrap melt, which resulted in improvement of the melt cleanliness. A very low concentration of lead was achieved by a zone melting treatment with repeated passage. This study reports on a pretreatment process for the reuse of solder scrap that is lead free.

In this study, Ti powders were fabricated from Ti scrap by the Hydrogenation-Dehydrogenation (HDH) method.The Ti powders were prepared from the spark plasma sintering (SPS) and their microstructure was investigated.Hydrogenation reactions of Ti scrap occurred at near 450oC with a sudden increase in the reaction temperature and thedecreasing pressure of hydrogen gas during the hydrogenation process in the furnace. The dehydrogenation process was alsocarried out at 750oC for 2 hrs in a vacuum of 10-4torr. After the HDH process, deoxidation treatment was carried out withthe Ca (purity: 99.5%) at 700oC for 2 hrs in the vacuum system. It was found that the oxidation content of Ti powder thatwas deoxidized with Ca showed noticeably lower values, compared to the content obtained by the HDH process. In orderto fabricate the Ti compacts, Ti powder was sintered under an applied uniaxial punch pressure of 40 MPa in the range of900-1200oC for 5 min under a vacuum of 10-4torr. The relative density of the compact was 99.5% at 1100oC and the tensilestrength decreased with increasing sintering temperature. After sintering, all of the Ti compacts showed brittle fracturebehavior, which occurred in an elastic range with short plastic yielding up to a peak stress. Ti improved the corrosionresistance of the Ti compacts, and the Pd powders were mixed with the HDH Ti powders.

In this study, Ti powder was fabricated from Ti scrap by the Hydrogenation-Dehydrogenation (HDH)method. Hydrogenation reactions of Ti scrap occurred at near 450oC with a sudden increase in the reactiontemperature and the decreasing pressure of hydrogen gas during the hydrogenation process in the furnace. Thedehydrogenation process was also carried out at 750oC for 2hrs in a vacuum of 10-4torr. After the HDHprocess, a deoxidation treatment was carried out with the Ca(purity: 99.5) at 700oC for 2hrs in the vacuumsystem. It was found that the oxidation content of Ti powder that was deoxidized with Ca showed noticeablylower values, compared to the content obtained by HDH process. In order to fabricate Ti compacts, Ti powderwas sintered at 1100~1400oC for 2hrs under a vacuum of 10-4torr. The relative density of compact was 94.9%at 1300oC. After sintering, all of the Ti compacts showed brittle fracture behavior, which occurred in an elasticrange with short plastic yielding up to a peak stress.

Pretreatment of eliminating FFA is needed to make biodiesel from animal fat recovered from leather wastes because its acid value is high. This study was carried out to investigate the influence of 4 different pretreatment methods, which are heterogeneous catalyst method, ion exchange resin method, low pressure.high temperature method, and alkali method on the eliminating FFA and fatty acid composition. The results showed that the rate of eliminating FFA increased in the order of alkali method > catalyst method > low pressure high temperature method > ion exchange method. In the case of pretreatment of alkali method using NaOH, the rate of eliminating FFA appeared more than 86% regardless of acid value. Therefore, it was considered that alkali method using NaOH was the most effective in the view of economical and productive aspects, taking it into account that the acid value of animal fat recovered from fleshing scrap generated during leather making processes was 7 to 8.

Fleshing scrap is a kind of wastes produced during leather making process and used in the test of manufacturing biodiesel. The early step of manufacturing biodiesel is fat recovery from fleshing scrap. Hence, we investigated the influence of the way of fat recovery on the fatty acid composition. We used three different recovery ways, that is chemical method by protein decomposition with acid/fat recovering, physical method by protein denaturalization with heat and vacuum/fat pressing, and biodiesel method by protein decomposition/fat recovering. The biological method yielded the best results in terms of appearance transparency. It was most effective to lower acid value. Also the recovered fat by biological method would be favorable methyl-ester reaction raw material for biodiesel because it contains more than 5% of oleic acid among unsaturated fatty acid.

In the present study, the focus is on the analysis of carbothermal reduction of oxide powder prepared from waste WC/Co hardmetal by solid carbon under a stream of argon for the recycling of the WC/Co hard-metal. The oxide powder was prepared by the combination of the oxidation and crushing processes using the waste hardmetal as the raw material. This oxide powder was mixed with carbon black, and then this mixture was carbothermally reduced under a flowing argon atmosphere. The changes in the phase structure and gases discharge of the mixture during carbothermal reduction was analysed using XRD and gas analyzer. The oxide powder prepared from waste hardmetal has a mixture of . This oxide powder reduced at about , formed tungsten carbides at about , and then fully transformed to a mixed state of tungsten carbide (WC) and cobalt at about by solid carbon under a stream of argon. The WC/Co composite powder synthesized at for 6 hours from oxide powder of waste hardmetal has an average particle size of .

알루미늄은 낮은 비중을 가지는 금속으로 철에 비하여 상대적으로 가볍고 비강도가 크므로 건축물의 외장 재료로 많이 사용되고 있다. 알루미늄의 경우 다른 금속에 비해 산화되기 어렵고 낮은 융점으로 인해 사용이 끝난 알루미늄 재료의 경우 녹여서 재활용이 가능하다. 건축물 외장 재료로 사용되는 복합 패널의 경우 철, 동, 강 등의 금속과 알루미늄이 결합된 구조로 되어 있고 알루미늄을 분리할 경우 쉽게 재활용이 가능한 장점을 가지고 있다. 이러한 복합 패널에서 사용되고 있는 알루미늄을 재활용하기 위해서는 결합된 소재들을 분리하는 단계가 필요하다. 알루미늄 복합 패널은 건축물 철거 시 발생하는 폐자재로 일정한 형태가 없고 크기가 다르므로 일반적인 재활용 장비에서 처리하기에는 어려운 상황이다. 일반적으로 대부분의 재활용 업체에서는 가열하거나 수작업을 통해 알루미늄을 분리하고 있지만 가열방식에서는 유해가스 배출로 인한 환경 문제와 수작업을 통한 높은 인건비 비용에 대한 문제점이 나타나고 있다. 따라서 본 연구에서는 다양한 형태의 복합 패널 폐자재(스크랩)를 효율적으로 재활용할 수 있는 설비 및 방법을 개발하는 것을 목적으로 한다. 개발된 장비를 통해 복합 패널을 일정한 크기로 분쇄하고 파쇄된 복합물에서 알루미늄과 폴리에틸렌을 분리하여 최종적으로 분리된 알루미늄을 일정한 크기의 그래뉼 입자로 만들었다. 구조해석을 통해 장비의 안전성을 검증하고 일정한 크기 및 순도를 가진 알루미늄 그래뉼 입자가 생성되는지를 확인하였다. 최종적으로 생산된 알루미늄 그래뉼 입자의 순도 및 크기를 분석하여 건축용 복합 패널 스크랩의 알루미늄 재활용성에 대한 평가를 분석하였다.

선반 스크랩은 금속 가공 공정에서 선반 및 밀링 작업에 의해 발생된 철강제품의 부산물이므로, 섬유보강 시멘트 복합체 제작시 이 를 활용할 경우 경제성뿐만 아니라 환경 친화적인 효과를 가져온다. 따라서 이 연구의 목적은 강섬유 대체재료로서 선반 스크랩의 활용 방안을 제시하기 위하여 선반 스크랩 보강 시멘트 복합체(LSRCCs)의 작업성 및 강도 특성을 평가하는 것이다. 이를 위하여 금속 가공공장에서 3종류 의 선반 스크랩을 채취한 후 폭 2 mm, 길이 40 mm로 가공하여 LSRCCs를 제작하였다. 그 결과, LSRCCs의 작업성은 플레인 모르타르보다 약 간 저하되었고, 휨강도는 크게 개선되었으며, 선반 스크랩의 종류가 LSRCCs의 특성에 다소 영향을 미치는 것으로 나타났다.

The purpose of this experimental research is to investigate the effect of types of lathe scrap on the characteristics of lathe scrap reinforced cementitious composites (LSRCCs). For this purpose, three types of lathe scraps were collected from processing plants of metal, and then LSRCCs containing these were made for 2mm width and 40mm length. As a result, it was observed from the test results that the compressive and flexural strength of LSRCCs were larger than these of plain mortar and effect of types of lathe scrap on the characteristics of LSRCCs were slightly large.