Case study in Korea of manufacturing SRF for polyurethanes recycling in e-wastes

Statistics showed that approximately 1,195,000 refrigerator units (116,094 metric tons) were recycled annually in Korea’s formal sector. Although the recycling level for these was satisfactory, collecting and processing polyurethane at recycling centers (RCs) posed several problems, including the risk of fire from the incinerator, the generation of fugitive dust, and the high cost of disposal. The objective of our study is to provide an overview of refrigerator recycling and to introduce polyurethane solid refuse fuel (SRF) manufacturing facilities. These facilities, installed at four regional RCs in Korea, have a capacity of 800 kg/h, a motor of 476 kWh, and cost $664,300 (USD) to construct (criteria two facilities). According to our examination of the physico-chemical properties of SRF product, all results in categories have been satisfied with the quality standards. In terms of finances, RCs can reduce the total disposal cost from $160–175 to $60 by installing facilities, which results in savings of (on average) $180,546 annually. The Metropolitan Electronics Recycling Center, for example, has reduced its costs by $180,880 each year. Their return on investment was calculated to be about 3 years and 8 months (assuming no operating expenses) or 7 years and 4 months (including operating expenses).     

Establishing methodology for evaluating refrigerant recovery and recycling equipment: institutional responses to climate change in South Korea

Journal of Material Cycles and Waste Management - This paper aims to propose testing methods and standards for evaluating refrigerant recovery and recycling equipment so that the methodology can be...     

Influence of ship emissions on ozone concentrations around coastal areas during summer season

The influence of ship emissions on ozone (O₃) concentrations in a coastal area (CA) including Busan port, Korea was examined based on a numerical modeling approach during a high O₃ episode. The analysis was performed by two sets of simulation scenarios: (1) with ship emissions (e.g., TOTAL case) and (2) without ship emissions (e.g., BASE case). A process analysis (PA) (the integrated processes rate (IPR) and integrated reaction rate (IRR) analyses) was used to evaluate the relative contributions of individual physical and chemical processes in O₃ production in and around the CA (e.g., sites of Dong Sam (DS) and Dae Yeon (DY)). The model study suggested the possibility that pollutant gases emitted from the ships traversing Busan port can exert a direct impact on the O₃ concentration levels in the CA. Largest impacts of ship emissions on the O₃ concentrations were predicted at the coast (up to 15 ppb) and at inland locations (about 5 ppb) due to both the photochemical production of pollutant gases emitted from the ships and meteorological conditions. From the PA, the photochemical production of O₃ (P(O₃)) due to ship emissions in the CA was found to increase by a mean of 1.5 ppb h^?1 (especially by ≥10 ppb h^?1 at the DS site) during the day.     

Source identification of particulate matter collected at underground subway stations in Seoul,Korea using quantitative single-particle analysis

Subway particle samples collected at four underground subway stations in Seoul, Korea were characterized by a single-particle analytical technique, low-Z particle electron probe X-ray microanalysis. To clearly identify indoor sources of subway particles, four sets of samples collected in tunnels, at platforms, near ticket offices, and outdoors were investigated. For the samples collected in tunnels, Fe-containing particles predominate, with relative abundances of 75–91% for the four stations. The amounts of Fe-containing particles decrease as the distance of sampling locations from the tunnel increases. In addition, samples collected at the platform in subway stations with platform screen doors (PSDs) that limit air-mixing between the platform and the tunnel showed marked decreases in relative abundances of Fe-containing particles, clearly indicating that Fe-containing subway particles are generated in the tunnel. PM₁₀ mass concentration levels are the highest in the tunnels, becoming lower as the distance of sampling locations from the tunnel increases. The extent of the decrease in PM₁₀ in stations with PSDs is also larger than that in stations without PSDs. The results clearly indicate that Fe-containing particles originating in tunnels predominate in the indoor microenvironment of subway stations, resulting in high indoor PM₁₀ levels, and that PSDs play a significant role in reducing Fe-containing particles at platforms and near ticket offices.     

Sequential soil washing techniques using hydrochloric acid and sodium hydroxide for remediating arsenic-contaminated soils in abandoned iron-ore mines

Sequential washing techniques using single or dual agents [sodium hydroxide (NaOH) and hydrochloric acid (HCl) solutions] were applied to arsenic-contaminated soils in an abandoned iron-ore mine area. We investigated the best remediation strategies to maximize arsenic removal efficiency for both soils and arsenic-containing washing solution through conducting a series of batch experiments. Based on the results of a sequential extraction procedure, most arsenic prevails in Fe-As precipitates or coprecipitates, and iron exists mostly in the crystalline forms of iron oxide. Soil washing by use of a single agent was not effective in remediating arsenic-contaminated soils because arsenic extractions determined by the Korean standard test (KST) methods for washed soils were not lower than 6mg kg(-1) in all experimental conditions. The results of X-ray diffraction (XRD) indicated that iron-ore fines produced mobile colloids through coagulation and flocculation in water contacting the soils, containing dissolved arsenic and fine particles of ferric arsenate-coprecipitated silicate. The first washing step using 0.2M HCl was mostly effective in increasing the cationic hydrolysis of amorphous ferrihydrite, inducing high removal of arsenic. Thus, the removal step of arsenic-containing flocs can lower arsenic extractions (KST methods) of washed soils. Among several washing trials, alternative sequential washing using 0.2M HCl followed by 1M HCl (second step) and 1M NaOH solution (third step) showed reliable and lower values of arsenic extractions (KST methods) of washed soils. This washing method can satisfy the arsenic regulation of washed soil for reuse or safe disposal application. The kinetic data of washing tests revealed that dissolved arsenic was easily readsorbed into remaining soils at a low pH. This result might have occurred due to dominant species of positively charged crystalline iron oxides characterized through the sequential extraction procedure. However, alkaline extraction using NaOH was effective in removing arsenic readsorbed onto the surface of crystalline minerals. This is because of the ligand displacement reaction of hydroxyl ions with arsenic species and high pH conditions that can prevent readsorption of arsenic.     

Characterization of Extruded Thermoplastic Starch Reinforced by Montmorillonite Nanoclay

The purpose of this study was to understand how the montmorillonite (MMT) nanoclay influences physical and mechanical properties of thermoplastic starch (TPS), which was produced by a conventional extrusion procedure. MMT nanoclay was added at 0, 4, and 8 % (w/w) concentrations. Transmission electron microscopy (TEM) showed most MMT platelets existed in tactoid structure in the starch matrix. In addition, FTIR spectra indicated TPS/MMT nanocomposites kept chemically stable after the extrusion. Tensile strength (TS) was about 7.0 MPa, while elongation-at-break (E) and elastic modulus (EM) were about 52 % and 32–41 MPa, respectively. Moisture sorption behaviour of the samples was well described by GAB and BET models. Thermal property tests exhibited the glass transition temperature (T _g ) of the nanocomposites decreased with increasing MMT from 0 to 8 %, indicating MMT nanoclay had a plasticization effect.     

Solidification of arsenic and heavy metal containing tailings using cement and blast furnace slag

The objective of this study is to examine the solidification of toxic elements in tailings by the use of cement and blast furnace slag. Tailings samples were taken at an Au-Ag mine in Korea. To examine the best mixing ratio of tailings and the mixture of ordinary Portland cement (OPC) and blast furnace slag (SG) of 5:5, 6:6, 7:3, and 8:2, the 7:3 ratio of tailings and OPC+SG was adapted. In addition, the mixing ratios of water and OPC + SG were applied to 10, 20, and 30 wt%. After 7, 14, and 28 days' curing, the UCS test was undertaken. A relatively high strength of solidified material (137.2 kg cm?2 in average of 3 samples) at 28 days' curing was found in 20 wt% of water content (WC). This study also examined the leachability of arsenic and heavy metals (Cd, Cu, Pb, and Zn) under the Korean Standard Leaching Test, and it showed that the reductions in leachabilities of As and heavy metals of solidified samples were ranged from 76 to 99%. Thus, all the solidified samples were within the guidelines for special and hazardous waste materials by the Waste Management Act in Korea. In addition, the result of freeze-thaw cycle test of the materials indicated that the durability of the materials was sufficient. In conclusion, solidification using a 7:3 mixing ratio of tailings and a 1:1 mixture of OPC + SG with 20% of WC is one of the best methods for the remediation of arsenic and heavy metals in tailings and other contaminated materials.     

Recycling of tailings from Korea Molybdenum Corporation as admixture for high-fluidity concrete

The main objective of this study is to develop an eco-friendly and a large recycling technique of flotation Tailings from korea (TK) from metal mines as construction materials such as admixtures for high-fluidity concrete (HFC). TK used in this study was obtained from the Korea Molybdenum Corporation in operation. TK was used as the alternative material to adjust flowability and viscosity of HFC in the form of powder agent which enables adjustment of concrete compressive strength. In this study, we have performed concrete rheological tests and concrete flowability tests to obtain the quality characteristics of TK for using as the admixture in producing HFC. The results indicated that the adequate mix ratio of cement to TK should be 8:2 (vol%). It is more effective to use the TK as admixture to control flowability, viscosity and strength of HFC than the normal concrete. It was found that TK could be recycled construction materials in bulk such as admixture for HFC, in terms of the economic and eco-friendly aspects.     

Material and heavy metal balance in a recycling facility for home electrical appliances

Collection and recycling of home electrical appliances was started in Japan in 2001 under a new recycling law. The law is aimed at promoting material recycling and at reducing the amount of waste to be landfilled. End of life products are processed by manual disassembly, shredding, and separation in 38 recycling facilities. The authors conducted a questionnaire survey and interviewed at some facilities to obtain information on process flow and material balance. By using the detailed records offered by one facility and by estimating the composition of recovered components, the material balance in the facilities was determined for four typical recycling processes. The heavy metal content of the recovered components was analyzed, then metal flow in the process was determined for each scenario. As a result, it was concluded that emissions to the environment of most heavy metals have been substantially reduced by the new recycling system, while a modest improvement in the rate of material recovery has been achieved.