• Resources Recycling
• /
• v.28 no.5
• /
• pp.30-41
• /
• 2019

Global production of zinc is about 13 million tons and zinc is the fourth-most widely used primary metal in the world following iron, aluminum and copper. When zinc is recycled to produce secondary zinc, it can save about 75 % of the total energy that is needed to produce the primary zinc from ore, and in therms of $CO_2$ emissions reduced by about 40 %. However, since zinc is mainly used for galvanizing of steel, the recycling rate of zinc is about 25 %, which is lower than other metals. The raw materials for recycling of zinc include dusts generated in the production of steel and brass, sludge in the production process of non-ferrous metals, dross in the melting of zinc ingots or hot dip galvanizing, waste batteries, and metallic scrap. Among them, steelmaking dust and waste batteries are most actively recycled up to now. Most of the recycling process uses pyrometallurgical methods. Recently, however, much attention has been given to a combined process of pyrometallurgical and hydrometallurgical processes.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
• /
• v.10 no.S_3
• /
• pp.139-148
• /
• 2001

Heavy metals such as Cu, Ni, Cd, and Pb were chemically extract from the contaminated soils using the chelating agents, EDTA and DTPA. These chemical extraction have been focused on its applicability to a wide range of soils. Results of extractive efficiency for heavy metal follow the order : Cu-EDTA $\geq$ Ni-EDTA > Pb-EDTA > Cd-EDTA > Cu-DTPA> Pb-DTPA. This result is coincided with order of conditional formation constants(Kr) of metal-chelate agent. The second study involved the recovery of the metals and EDTA from complex solutions by an electromembrane process. The overall processes of regeneration, recovery, and reuse were evaluated. The electrochemical studies showed that copper could be chosen as an electrode to plate Cd, Cu, and Pb. At least 95% of 75 of EDTA and associated Cu or Pb could be recovered by the electromembrane process. Recovery of Cd by electodeposition was not possible with the copper electrode. The percent EDTA recovery is equal to the percentage of metal electroplated from the chelates.

• Resources Recycling
• /
• v.13 no.1
• /
• pp.28-38
• /
• 2004

The characteristics of cyanide decomposition in aqueous phase by electric oxidization have been explored in an effort to develop a process to recycle waste water. Considering current efficiency and voltage, the free cyanide decomposition experiment by electric oxidization indicated that 5 V of voltage and copper catalytic Cu/CN mole ratio 0.05 was the most appropriate condition, where current efficiency was 26%, and decomposition speed was 5.6 mM/min. High voltage and excess copper addition increased decomposition speed a little bit but not current efficiency. The experiment of free cyanide density change proves that high density cyanide is preferred because speed and current efficiency increase with density. Also, the overall decomposition reaction could be represented by the first order with respcect to cyanide with the rate constant of $1.6∼7.3${\times}$10^{-3}$ $min^{-1}$ The mass transfer coefficient of electric oxidization of cyanide came out as $2.42${\times}$10^{-5}$ $min^{-1}$ Furthermore, the Damkohler number was calculated as 5.7 in case of 7 V and it was found that the mass transfer stage was the rate determining step.

• Journal of Korean Society of Environmental Engineers
• /
• v.36 no.2
• /
• pp.139-146
• /
• 2014

In this research, we quantified the environmental load while using and not using secondary resources. During the process of primary processed product of metal resources (copper, aluminum), we applied LCA technique and analyzed by dividing into 8 environmental impact categories that affect the environment. Furthermore, we analyzed the greenhouse gas that occur during the process of primary processed product domestically and globally according to the changes of each metal resource's recycling rate. Consequently, when producing 1 ton of copper using secondary resources, the environmental effects were found to be 6.09E + 01 person-yr/f.u. and 7.23E + 01 person-yr/f.u. Additionally, as the recycling rate increased both globally and domestically, the amount of greenhouse gas decreased. Producing 1 ton of Aluminum using secondary resources, the environmental effects were found to be 2.34E + 02 person-yr/f.u. and 3.01E + 02 person-yr/f.u. Moreover, as the recycling rate domestically decreased, the amount of greenhouse gas increased, however the globally was decreased.

• Resources Recycling
• /
• v.27 no.6
• /
• pp.23-29
• /
• 2018

Recently rapid economic growth and technological development have led to an increase in the generation of waste electrical and electronic equipment (WEEE). As the amount of electric and electronic waste generated increases, the importance of processing waste printed circuit boards (PCB) is also increasing. Various studies have been conducted to recycle various valuable metals contained in a waste PCB in an environmentally friendly and economical manner. To get anode slime containing Ag and Au, Anode copper prepared from PCB scraps was used by means of electro-refining. Ag and Au recovery was conducted by leaching, direct reduction, and ion exchange method. In the case of silver, the anode slime was leached at 3 M $HNO_3$, 100 g/L, $70^{\circ}C$, and Ag was recovered by precipitation, alkali dissolution, and reduction method. In the case of gold, the nitrate leaching residues of the anode slime was leached at 25% aqua regia, 200 g/L, $70^{\circ}C$, and Au was recovered by pH adjustment, ion exchange resin adsorption, desorption and reduction method. The purity of the obtained Au and Ag were confirmed to be 99.99%.

• Proceedings of the Korean Institute of Resources Recycling Conference
• /
• 2006.05a
• /
• pp.86-89
• /
• 2006

전해 생성된 염소를 이용하여 구리를 침출하는 연구를 수행하였다. 염산농도 $1molL^{-1}$, 반응온도 $25^{\circ}C$, 교반속도 400rpm 조건에서 전류밀도 $10mA/cm^{2}$의 경우 반응온도에 상관없이 구리의 침출속도가 동일하였으나 $Cl_{2}$ 생성량이 충분한 $40mA/cm^{2}$의 경우 온도가 높을수록 구리의 침출속도가 증가하였다. 침출된 구리농도가 6g/L 부근에 도달하면 염소의 공급속도에 상관없이 구리의 침출이 둔화되었다. 이는 구리-염소 착화물의 형성과 관련된 것으로 생각된다.

• Resources Recycling
• /
• v.6 no.3
• /
• pp.36-40
• /
• 1997

A series of processes has been developed to recover the gold from electronic scrap containing about 200~600 ppm Au. First, mechanical beneficiation including shredding, crushing and screening was employed. Results showed that 99 percent of gold component leaves in the fraction of under 1mm of crushed scrap and its concentration was enriched to about 800 ppm without incineration. The crushed scrap was leached in 50% aqua regia solution and gold was completely dissolved at $60^{\circ}C$ withing 2 hours. Other valuable metals such as silver, copper, nickel and iron were also dissolved. The resulting solution was boiled to remove nitrous compounds in the leachate. Finally, a newly designed electrolyzer was tested to recover the gold metal. More than 99% of gold and silver were recovered within an hour by electrowinning process.

• Resources Recycling
• /
• v.20 no.3
• /
• pp.12-27
• /
• 2011

DOWA group has been working on metal recycling applying the smelting and refining process of KOSAKA Smelter. DOWA has developed it's metal recycling technologies through the treatment of black ore(complex sulfide ores) that contain many kinds of non-ferrous metals. In addition to these special technologies, DOWA has strengthened its hydrometallurgical process of precious metals and ability to deal with low-grade materials such as used electrical appliances or vehicles. On the other hand, JX Nippon Mining & Metals Corporation(JX-NMMC) carries out its metal recycling and industrial waste treatment businesses employing advanced separation, extraction and refining technologies developed through its extensive experience in the smelting of non-ferrous metals. JX-NMMC collects approximately 100,000t/y of copper and precious metal scraps from waste sources such as electronic parts, mobile phones, catalytic converters, print circuit boards and gold plated parts. These items are recycled through the smelting and refining operations of Saganoseki smelter and Hitachi Metal-recycling complex(HMC). In this like, metal recycling industries combined with environmental business service in Japan have been developed through excellent technologies for mineral processing and non-ferrous smelting. Also, both group, Dowa and JX-NMMC, were contributed to establish Japan's recycling-oriented society as the typical leading company of non-ferrous smelting. Now. it is an important issue to set up the collection system for e-waste.

• Journal of Environmental Science International
• /
• v.26 no.1
• /
• pp.119-131
• /
• 2017

This study evaluated the feasibility of recovering and recycling nitrogen (N) and phosphorus (P) from livestock excreta as struvite ($MgNH_4PO_4{\cdot}6H_2O$) in South Korea. Our experimental results showed that struvite precipitation was a very effective way to recover N and P from livestock excreta. Moreover, our study demonstrated that struvite precipitates from livestock excreta (SPL) contain higher concentrations of N, P, and magnesium (Mg) as compared to compost and liquid manure from livestock excreta. In addition, although SPL contain high concentrations of copper (Cu) and zinc (Zn), they meet the fertilizer criteria for concentrations of heavy metals. In South Korea, SPL cannot currently be used as a fertilizer due to legal constraints. Legal permission for SPL use would offer greater choice in livestock excreta management. In conclusion, recovery and recycling of N and P from livestock excreta as struvite can be an effective tool for managing nutrients in livestock excreta.

• Resources Recycling
• /
• v.25 no.3
• /
• pp.37-42
• /
• 2016

Highly efficient and environmentally friendly mechanical process was developed for the higher recovery rate and productivity in the recycling of waste jelly-filled communication cables. Only the simplest mechanical method was designed and built for a continuous process, further proved experimentally along with the addition of several parts such as brush-type rollers and scrappers. In this process, the recovery rate and productivity were 98% and 55 Kg/hr respectively. This process is thought to be simple but highly advanced method for the commercialization of green process.