Amalgamation Method Research Articles

Effect of Applied Voltage Value on Lithium 6 Isotope Enrichment By Intermittent Voltage Application Electrodialysis Method

Thermonuclear fusion power generation assumes a nuclear fusion reaction between deuterium and tritium. Deuterium is abundant in seawater, and it is assumed that it can be recovered from there. Tritium rarely exists in nature. Therefore, tritium must be produced through a nuclear fission reaction between lithium and neutrons. Lithium exists stably in nature in the states of lithium 6 (6Li) and lithium 7 (7Li), and the isotope ratio is 6Li/7Li = 7.6/92.4. From the perspective of lithium production rate and energy balance, it is necessary to supply lithium with an isotope ratio of 6Li/7Li ≥ 90/10. The mercury amalgam method is the only practical method, but it has a large environmental impact [1]. Therefore, new 6Li isotope enrichment methods are being explored. One promising method is electrodialysis. Hoshino et al. reported that 6Li isotope enrichment could be achieved by electrodialysis using a porous polymer membrane impregnated with a liquid electrolyte [2, 3]. We have previously reported that 6Li isotope enrichment efficiency can be improved by applying a voltage with an appropriate intermittent profile to the front and back surfaces of the diaphragm of a lithium-ion conductive solid electrolyte membrane [3]. Here we investigated the effect of applied voltage during intermittent profile electrodialysis on isotope enrichment rate and lithium transfer rate. The isotope enrichment rate was determined by inductively coupled plasma mass spectrometry. In continuous voltage application, the 6Li isotope enrichment rate decreased as the applied voltage increased, but in intermittent voltage application, the 6Li isotope enrichment rate did not decrease as the applied voltage increased. Increasing the applied voltage increased the lithium transfer rate.[1] S. C. Brooks, G. R. Southworth, Environmental Pollution, 159, (2011) 219−228.[2] T. Hoshino, T. Terai, Fusion Eng. Des., 86(9-11), (2011) 2168-2171.[3] T. Hoshino, T. Terai, J. Nuclear Materials, 417, (2011) 696-699.[4] S. Honda, K. Shin-mura, K. Sasaki, J. Ceram. Soc. JPN, (2018) 331-335.

Penerapan Metode Enhanced Phytoremediation pada Lahan Bekas Tambang Emas Desa Tirta Kencana Kecamatan Bengkayang

Community gold mining activities using the amalgamation method cause soil pollution due to the use of mercury (Hg) to extract gold content which causes a decrease in soil quality and environmental damage. Enhanced phytoremediation is a method that can be applied to remove mercury levels with using the Cyperus kyllingia plant and adding supporting elements in the form of bacterial isolates that are resistant to mercury. This research aimed to determine the effectiveness of Cyperus kyllingia plants and bacterial isolates for removing mercury levels in mercury-contaminated soil, as well as observing the bacterial population and plant morphology during the research. Based on the research results, it is known that the best efficiency value for removing mercury levels is found in phytoremediation with the addition of bacterial isolates, namely 86.88%. The largest bacterial population was found in the phytoremediation reactor with the addition of bacterial isolates, namely 73.3 × 106 CFU/mL. The mercury content in polluted soil causes changes in plant morphology, namely the color of green plants changes to yellow, but plants can reproduce as indicated by an increase in the number of leaves and plant stems

The effect of cow manure amendment and the ratio of gold mine tailings on sweet potato gold phytomining

Artisanal and small-scale gold mining has commonly used the mercury amalgamation method for gold ore extraction. The processing waste or tailings often contain gold and other metals. This study examined the effects of cow manure amendment and the ratio of gold mine tailings on sweet potato (Ipomoea batatas L.) gold phytomining. The pot experiment was conducted in the Faculty of Agriculture greenhouse at Padjadjaran University in Indonesia. The sweet potato MZ119 clone (an orange-fleshed sweet potato) was planted on a polybag (40 x 40 cm) consisting of 10 kg of planting media, which was a mixture of gold mine tailing and soil. The design used was a completely randomized design factorial with three replications. The first factor was ratios of gold mine tailing consisting of three levels, namely 30%, 50%, 70%, and 100% (w/w). The second factor was doses of organic manure, namely without cow manure, 250 g pot-1, 500 g pot-1, and 750 g pot-1. The results demonstrated that the application of cow dung and the gold mine tailings ratio (w/w) had a significant (p = 0.05) effect on plants' dry weight biomass, gold accumulation, and gold phytomining by sweet potato. The highest gold mass yield of 0.066 mg gold plant-1 was achieved by a 50% (w/w) gold mine tailing ratio and 750 g pot-1 cow manure treatment.

Potential Combination of Phytoremediation Plants and Compost in Remediation of Hg in Ex-Gold Mine Soil Contaminated Mercury (Hg)

Heavy metal mercury pollution in the environment can have negative impacts on both surrounding ecosystems and human health. Sources of mercury pollution often come from mining activities, particularly from many unlicensed gold mines (PETI) that use the mercury amalgamation method to extract gold. Due to the persistent, bioaccumulative, and toxic nature of mercury, contamination in the soil has increased. One effort to reduce mercury toxicity is the application of absorption methods using phytoremediation plants and compost as regulating factors. The aim of this study is to review sources of information related to the use of phytoremediation plants and the application of compost as remediators to clean mercury (Hg)-contaminated soil. To reduce levels of heavy metal contamination, plants employ five phytoremediation mechanisms: phytoextraction, phytostabilization, rhizofiltration, phyto degradation, and phytovolatilization. Therefore, selecting hyperaccumulator plants that have the ability to accumulate mercury (Hg) at levels 100 times higher than ordinary plants is crucial for effective remediation. Additionally, the use of compost as a source of organic material can enhance mercury mobility. The addition of organic materials such as compost can increase C organic content, cation exchange capacity (CEC), pH, and Hg-chelate formation, thereby maximizing mercury absorption by plants. This combination has a positive impact on reducing mercury levels in the soil and is environmentally safe.

Research progress on lithium isotopes separation by chemical exchange with crown ethers decorated materials

The separation of lithium isotopes (6Li and 7Li) is of great importance for the nuclear industry. The lithium amalgam method is the only lithium isotopes separation process in industry, and the extensive use of mercury has raised concerns about its potential environmental hazards, which have prompted the search for more efficient and environmentally friendly alternatives. Crown ethers can bind lithium ions highly selectively and separate lithium isotopes effectively. A chemical exchange-based lithium isotopes separation method using crown ether decorated materials could be a viable and cost-effective alternative to the lithium amalgam method. In this review, we provide a systematic summary of the recent advances in lithium isotopes separation using crown ether decorated materials.

Single step synthesis of sulfidated nanoscale iron modified kaolin clay for hexavalent chromium remediation from groundwater

Remediation of dissolved hexavalent chromium [Cr(VI)] is often achieved by iron nanoparticles [nZVI], sulfidated nZVI [SnZVI], and adsorption on clay minerals. Although different types of nZVI effectively removed Cr(VI), performance evaluation of nZVI modified with low-cost and naturally available kaolinite clay was not thoroughly studied. In the present research, kaolin was modified with nZVI (K-nZVI) and SnZVI (K-SnZVI) at two different kaolin to iron mass ratios (kaolin: Fe). Both K-nZVI and K-SnZVI were synthesized by a simple one-step process, avoiding complicated amalgamation methods of modified nZVI. Effects of ionic strength, pH, major cations, and anions in Cr(VI) remediation efficiencies were probed. Kinetics of Cr(VI) removal was quantified from sacrificial batch studies. Further experiments were performed in Cr(VI)-spiked synthetic groundwater matrix in the respective pH and initial Cr(VI) ranges of 5.5–8 and 2–100 mg L−1. With maximum Cr(VI) remediation efficiencies of 100% (K-nZVI) and 98% (K-SnZVI) in synthetic groundwater contaminated with 2–100 mg L−1 Cr(VI), both of these materials might be effectively used for groundwater treatment. The usage of kaolin—an analog of the natural kaolinite clay—with relatively decreased Fe content in the nanoparticles would reduce the treatment cost and provide insight into a sustainable solution for Cr(VI) contamination.

ANALYSIS OF BIOACCUMULATION OF BIOMERCURY (Hg) IN HAIR AND ITS IMPACT ON THE HEALTH OF MINING WORKERS IN MALOMBA VILLAGE, DONDO SUB-DISTRICT, TOLITOLI DISTRICT

Mercury is a dangerous and toxic material, persistent, bioaccumulates, and harmful to human health. Mercury is used in the gold processing process using the amalgamation method carried out by people in gold mining without permits. Exposure to mercury in gold processing can occur through direct contact with the skin and inhalation of mercury vapor. Mercury exposure in the body can be analyzed using hair, So this study aims to determine the levels of mercury that accumulate in the hair of mine workers and the impact of mercury content in hair on the health problems of gold mine workers in Malomba Village. The hair samples used were destroyed using H2SO4, and HNO3: HCl (1:3) and analyzed using a cold vapor type Atomic Absorption Spectrophotometer (CV-AAS) at a wavelength of 253,7 nm. The results obtained are, the highest mercury level was 9,82 μg/g, the lowest mercury level was -0,10 μg/g and the control sample was 3,91 μg/g. The limit of mercury levels in hair according to the WHO is 1 μg/g, so the mercury level in respondents KL does not exceed the threshold, while the other 9 respondents exceed the provisions of the mercury threshold in hair, and there are 2 respondents who have symptoms of mercury exposure, namely respondent YP showing symptoms of mercury exposure in the form of tremors, frequent tingling, itching, weakness of taste buds, difficulty swallowing, diarrhea, and headaches, while respondents OP showed symptoms of mercury exposure in the form of frequent tingling, itching, easy fatigue, headaches and eye irritation.

ANALYSIS OF MERCURY (HG) CONTENT IN URINE AND ITS IMPACT ON HEALTH DISORDERS OF ILLEGAL GOLD MINING WORKERS IN MALOMBA VILLAGE, DONDO SUB-DISTRICT, TOLITOLI DISTRICT

Mercury is a heavy metal element that very easily enters the bodies of living creatures and joins the food chain. The living creatures most likely to be directly exposed to mercury are traditional miners who use the amalgam method to extract gold ore. The danger of poisoning posed by mercury for humans can be diagnosed through analysis of mercury levels in urine. Furthermore, this research aims to determine mercury levels in the urine of gold mine workers and to obtain information regarding the mercury content in the urine and the health problems of gold mine workers. The method used in this research was the calibration curve method with Cold Vapor Atomic Absorption Spectophotometry (CV-AAS) analysis and descriptive methods from the results of questionnaire interviews. The results show that the mercury levels in mine workers have exceeded the threshold value set by WHO of 4 ppb while the highest mercury level obtained is 44.1 ppb, the lowest mercury level is 8.38 ppb and the control sample is 6.32 ppb, and there are 2 respondents that have symptoms of mercury exposure, namely respondent OP showing symptoms of mercury exposure in the form of frequent tingling, itching, easy fatigue, headache and eye irritation, and respondent YP showing symptoms of mercury exposure in the form of tremors, frequent tingling, itching, weakness of taste buds, difficulty swallowing, diarrhea, and headache. Based on the research results, it is found that the bodies of mining workers in Malomba Village show symptoms of exposure to mercury.

An investigation into cut surface quality of Al6061/Al2O3/B4C composite using hydro-abrasive machining process

The modern era has realized the tremendous potential of metal matrix composites (MMCs) in slowly substituting the traditional materials used in automotive and aerospace industries. Traditional machining of second generation MMCs is quite challenging due to heat generation, tool wear, and low cut surface quality. This work presents an analysis on hydro-abrasive machining (HAM) of the Al6061/Al2O3/B4C composite by using an amalgamated method of gray incidence based response surfaces (GIRS) to produce a good surface quality. The influence of HAM variables [abrasive flow rate (FA), waterjet pressure (PWJ), jet traverse speed (SJT), and stand-off distance (DS)] on various cut surface characteristics [surface roughness (Ra), striation-free zone (SFZ), striation angle (ΘS), and kerf angle (ΘK)] is examined using L27 OA and response surface plots. A hybrid approach of the GIRS method is presented for necessary polynomial modeling and simultaneous optimization. The reduction of response values is primarily influenced by the waterjet pressure and jet traverse speed. An optimal cutting condition resulted in a significant reduction in surface roughness by 19.22% and striation angle by 10.82%. The improvements in striation-free zone and kerf angle were also notable with reductions of 7.89% and 4.74%, respectively. FESEM images of machined surfaces, profile graphs of surface roughness, and images observed using atomic force microscopy were also studied.

The Amalgamation Formulae and Iterations of Mono-digit Pedigree

In this paper we present equations to generate the concatenation of natural numbers A∈N. The main ingredient of our study is the innocuous repunit of a number R_A ; and in this study we introduce three amalgamation operators: ↕ for the constant, ↑ for the incremental and ↓ for the detrimental cases of concatenation according to a variable arithmetic progression. Our method of amalgamation demonstrates the generation of common number sequences, as well as how any two different natural numbers can be joined and alternated, depending on which of the numbers should be displayed first. We also introduce an operator Ω(A ) based on repunits and whose dynamics yields two constants H_(o )and H_(e )which we calculate. Amongst the few corollaries from this conjecture is an identity stating that the product of the repunits of those irrational numbers R_(H_o ) R_(H_e )is equal to unity.

Mercury deposition to lake sediments near historic gold mines in northern Canada

Mercury (Hg) contamination in aquatic systems can lead to adverse human and environmental health outcomes. Yellowknife, a city in Canada’s Northwest Territories, is a historic mining community, with two large gold mines (Giant Mine and Con Mine) that used Hg amalgamation methods to extract gold between ∼1938 and 1960. We analyzed dated sediment cores from 20 small lakes to investigate the spatial and temporal Hg deposition patterns within 50 km of Giant Mine. Breakpoint analysis of the within-lake z-score normalized anthropogenic Hg flux indicates two significant time periods of changing emission rates. The first is a significant increase in Hg deposition rate (∼1925) during the time of gold exploration in the region and onset of Hg amalgamation (1938) and the second is a significant decrease in deposition rate that begins around the time of the cessation of Hg amalgamation at Giant Mine (∼1959). Sediment Hg concentrations exceeded the Canadian Council for Ministers of the Environment Interim Sediment Quality Guideline (ISQG) for Hg (0.17 mg/kg dw) in 55% of the lakes (n = 11) during mining (1948–1999). All lakes within 5 km of the Giant Mine roaster stack exceeded CCME ISQG during mining (n = 8), with a 4-fold increase in total Hg concentration observed during mining at these near-field (<5 km from stack) sites. We observed evidence of enriched Hg in near-field, mid-field, and far-field sites. The elevated sedimentary Hg concentrations during mining in near-field sites would have posed a hazard to human and wildlife health during the height of emissions, however the significant decrease in Hg concentrations since the closure of mines in the region demonstrate the potential for recovery in these aquatic ecosystems.

Preliminary phytotoxicity of Mercury in conventional gold mining wastewater on Typha latifolia and Pistia stratiotes

Small-scale mining, or conventional mining, is quite common in Indonesia. Almost all of these artisanal mining activities disregard environmental safety around the mining areas. The current widely used gold extraction method for gold exploitation is the amalgamation method, which utilizes mercury (Hg). The use of this method can result in environmental pollution from mercury. Based on the impact of mercury that can contaminate the environment, it is necessary to treat gold mining wastewater before disposing of it into the environment. One alternative that can be used to treat gold mining wastewater is to use plants (phytotreatment). The aims of study was to observe the tolerance of Hg to Typha latifolia and Pistia stratiotes plants, The methods was call the Range Finding Test (RFT). The study was conducted using synthetic Hg at concentrations of 0.3, 0.7, 1, 3, and 6 mg/L and a control (0 mg/L) in a batch reactor. The reactors were added with soil up to 25% as a growing medium. The physical observations of plants were carried out for 28 days. Typha latifolia and Pistia stratiotes could both grow and thrive at a Hg content of 6 mg/L, according to physical observations of the plants. In the first seven days, Pistia stratiotes plants exhibited a stress reaction in the form of yellowing and falling leaves. Both plants had vigorous, extended root development in all concentrations. Based on these findings, phytotreatment can be utilized as an alternate therapy to lower the Hg levels in gold mine wastewater.

‘I am not data’: A GAN simulation in tandem with Second Nature

‘I am not data’ has been produced in collaboration with a creative coder from the Netherlands. Over a period of six months around 4600 images were chosen from approximately 20,000 images of LatinX femmes. The images were then fed into a generative adversarial network (GAN) simulation that produced this film. The resulting work seeks to elucidate a process of lumping together foreign bodies as a method of amalgamation that works to create ‘new’ information. It exists in tandem with ‘Second Nature’, a body of work on Mexican femme bodies and algorithmic web searches, from which some images are included in this article. The process behind the GAN used for this film becomes a mere reference to a human shape. Its processes of synthesis work as a metaphor for systems of human classification in which the bodies of foreigners become fuel for monstrous stereotypes. There is a sense of history repeating itself through the ways that these technological tools are used in artificial intelligence (AI) which launches questions regarding equality and progress in pursuit of social justice.

Design of a miniature rectangular patch antenna for 5G applications

The demands of tiny, high data rates and wide bandwidth systems have led to the development of the fifth generation (5G) communication technology. In this paper, a compact rectangular patch antenna employing amalgam method (AM) is developed to fulfill these requirements. The AM is formed by combining a slotted patch with a faulty partial ground structure. The operating frequency is selected as 3.5 GHz for 5G applications (2.9 to 4.4 GHz). FR4_epoxy dielectric substrate material having a size of 30 mm × 20 mm is used to design the proposed antenna, which has a dielectric constant of 4.4, a thickness of 0.8 mm, and a loss tangent of 0.02. A microstrip feedline method with a characteristics impedance of 50 Ω is used to excite the patch. The antenna is designed and simulated by utilizing high-frequency structure simulator (HFSS) software. The outcomes of the simulation show that the antenna achieves a bandwidth of more than 1.2 GHz, VSWR of 1.18, peak gain of 2.50 dB with a directivity of 2.67 dB, and efficiency of 96.25%

Ag and Sn Implications in 3-Polker Coins Forgeries Evidenced by Nondestructive Methods.

Several forged 3-Polker coins have been reported in historical sources on the financial crisis that occurred between 1619 and 1623 at the start of the 30-year-long war. Supposedly, belligerent countries forged other countries' coins which were then used for external payments as a war strategy. Thus, a lot of 3-Polker coins (e.g., Sigismund-III-type) were forged, and the markets became flooded with poor currency. In the present day, these pre-modern forgeries are rare archeological findings. Only five forged 3-Polker coins randomly found in Transylvania were available for the current study. There are deeper implications of silver and tin in the forgery techniques that need to be considered. Thus, the forged 3-Polker coins were investigated via nondestructive methods: SEM microscopy coupled with EDS elemental spectroscopy for complex microstructural characterization and XRD for phase identification. Three distinct types of forgery methods were identified: the amalgam method is the first used for copper blank silvering (1620), and immersion in melted silver (1621) is the second one. Both methods were used to forge coins with proper legends and inscriptions. The third method is the tin plating of copper coins (with corrupted legend and altered design) (1622, 1623, and 1624). The EDS investigation revealed Hg traces inside the compact silver crusts for the first type and the elongated silver crystallites in the immersion direction, which are well-attached to the copper core for the second type. The third forgery type has a rich tin plating with the superficial formation of Cu6Sn5 compound that assures a good resistance of the coating layer. Therefore, this type should have been easily recognized as fake by traders, while the first two types require proper weighing and margin clipping to ensure their quality.

Solidification and stabilization of mercury-contaminated tailings in artisanal and small-scale gold mining using tras soil

Artisanal and small-scale gold is known to be sources of mercury pollution. This mercury contamination occurs when gold is isolated by the amalgamation method, contamination occurs. Mercury pollution in small-scale artisanal gold mining in the Kulon Progo area of Yogyakarta, the lowest tailing content was 164.49 mg kg&lt;sup&gt;-1&lt;/sup&gt;, and the highest was 383.21 mg kg&lt;sup&gt;-1&lt;/sup&gt;. This value exceeded the quality standard stipulated by Indonesian Government Regulation 22 of 2021 of 75 mg kg&lt;sup&gt;-1&lt;/sup&gt;. The technology that can control pollution is stabilization/solidification (S/S). This research aimed to determine the optimum composition of the tailings mixture with tras soil. Variations in the design of tras soil with tailings were 100:0, 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, and 10:90. The results showed that the optimum tras: tailings soil composition was 90:10, with a compressive test of 31 t m&lt;sup&gt;-2&lt;/sup&gt;. Toxicity Characteristic Leaching Procedure (&lt;em&gt;TCLP&lt;/em&gt;) was 0.0033 mg L&lt;sup&gt;-1&lt;/sup&gt; according to the quality standard of Indonesian Government Regulation no. 22, 2021, with a value of 0.05 mg L&lt;sup&gt;-1&lt;/sup&gt;. The compressive strength results follow the quality of the US EPA of 35 t m&lt;sup&gt;-2&lt;/sup&gt;.

Mercury Reduction on Gold Extraction in Artisanal and Small-Scale Gold Mining. A Case Study in Pelangan Village, West Nusa Tenggara Province, Indonesia

The most common method used for gold processing in artisanal and small-scale mining is amalgamation using mercury as a gold extracting agent. Indonesia is one of the countries that ratify the Minamata Convention, meaning that Indonesia has agreed to reduce or even eliminate the use of mercury. Some methods for replacing mercury as a gold-extracting agent are cyanidation and borax. The research aims to determine whether the miners in Pelangan still use mercury in gold processing. The method of this research is observation, interviews, and literature review. The data obtained were then analyzed descriptively. The result indicates that the miners in Pelangan Village use two methods of gold processing from ore: (1) amalgamation using mercury followed by cyanidation and (2) cyanidation. Most of the miners use the cyanidation method without going through amalgamation. The main reason they do not use mercury are amalgamation method yields low gold recovery and the price of mercury is high. This indirectly shows that the miners in Pelangan Village have contributed to efforts to reduce mercury use in Indonesia.

Description of Mercury Poison Clinical Symptoms in Workers and Communities Around the Small-Scale Gold Processing Area

The traditional gold processing process in Paya Seumantok Village, Krueng Sabee District, Aceh Jaya Regency, Aceh Province, is carried out using the amalgamation method which still uses mercury in the process, so it poses a risk to the health of workers and the surrounding community. This study aims to obtain an overview of the clinical symptoms experienced by workers and the community around the gold processing area. This study uses qualitative research methods with the number of community respondents were 90 respondents, and the number of worker respondents were 10 workers. Based on the results, the common acute clinical symptoms experienced by the community were headache (48.6%), cough (39.6%), abdominal pain (37.8%), diarrhea (29.7%), and hip pain (25.2%). While the chronic clinical symptoms experienced by the majority of community respondents were headaches (47.7%), irritability (27.9%), insomnia (26.1%), muscle cramps (23.4%), and weight loss (20.7%). Moreover, the most common acute clinical symptoms experienced by workers were cough (8 respondents), pelvic pain, diarrhea, abdominal pain, vomiting, nausea, and headaches were experienced by 7 respondents respectively. While for chronic clinical symptoms, the majority of workers experienced headaches and insomnia (8 respondents), irritability (6 respondents), anxiety (6 respondents), muscle cramps (5 respondents), and tremors (4 respondents). Based on the result, it can be concluded that the clinical symptoms encountered by the community and workers in the gold processing area have not shown clinical signs that are quite dangerous.

Gambaran logam berat merkuri (Hg) pada kuku penambang emas di Nagari Koto Tuo, Sijunjung Sumatera Barat

Unlicensed Gold Mining (PETI), was found in 4 districts in West Sumatra including, Dharmasraya covering an area of 1,773 ha, Solok 1,533 ha, Solok Selatan 2,559 ha, and Sijunjung 1,103 ha. PETI is a traditional gold mining activity, the results are processed using the amalgamation method. The amalgamation process in the PETI activity will result in environmental degradation caused by the washing process carried out in the river and the process of refining gold ore by burning which produces mercury vapor (Hg) which evaporates in the air. The amalgamation process can cause negative impacts in the form of environmental pollution by mercury vapor as a result of the process. As much as 10 - 30% of the mercury used in the gold amalgamation process will be released into the environment. The main health problems caused by mercury vapor occur in the brain, lungs, central nervous system and kidneys. The purpose of this study was to describe the level of toxicity that occurs in humans through nails on illegal gold miners in Nagari Koto Tuo Sijunjung, West Sumatra. The benefit of the research is as information that is conveyed to local governments and people who are exposed to heavy metals for the dangers they face. The research method is an observational study with a cross sectional study design, which is a study in which the variables including risk factors and variables including effects are observed simultaneously at the same time. The number of samples used in this study were 13 people. Samples were taken using accidental sampling technique. The method used to determine levels of metallic mercury in nails is wet destruction and examined by AAS. The results of this study used 13 active gold miners with a working period of 20.10 and 5 years with mercury levels of 10.31 mg/kg, 10.04 mg/kg, and 7.30 mg/kg. Based on the results of the standard deviation (SD) test, it was found that the average level of mercury in the nails of gold miner Koto Tuo, Sijunjung was 9.21 mg/kg with an average working life of 34 years and a standard deviation of 1.665. Mercury is a neurotoxin if used in high doses can damage the person's organs.

INFLUENCE OF PHASE CHANGE MATERIALS (PCMs) ON POLYURETHANE (PU) FOAM FIRE-RETARDATION

Polyurethane (PU) foam is a material that has long been regarded as a good thermal insulator for building purposes due to many advantageous attributes, such as cost and feasibility. Yet, to further develop its performance, many studies have focused on the potential of using the micro-structure of PU foam as an encapsulation for PCMs. Despite the apparent advantageous outcome of this premise, from the perspective of thermal performance, fire-retardation issues may pose as a threat. PU foam is known for its inherent poor fire-retardation properties. With the addition of PCMs, especially wax-based, it is possible that the fire-retardation would worsen. This would translate into additional costs in terms of application of treatments to counter the disadvantageous hazardous properties. In this study, an empirical investigation is carried out with the aim of determining whether addition PCMs to PU foam would influence its retardation, and to which extent. In this context, granules of wax-based PCMs are encapsulated in to closed-cell rigid PU foam via a simplified amalgamation method. Two concentrations of PCM content are presented in this paper. Then, fire-retardation testing is performed on specimens to compare the performance of the created PU/PCM specimens with this of regular PU specimens. The outcome of this empirical investigation further confirms that addition of PCM to PU foam is disadvantageous in terms of fire-retardation, and that the amount of added PCM is of considerable influence on this.