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• MakaleYalnız künye2026/r/gumushane/16329
  Selective extraction of rare earth elements from end-of-life NdFeB magnets via low-temperature NH4Cl-based chlorination roasting and water leaching

  Kumas, Cavit; Prasetia, Hendra; Sumardi, Slamet; Astuti, Widi; Mufakhir, Fika Rofiek; Daulay, Amru; Wicaksono, Mahruri Arif

  Neodymium-iron-boron (NdFeB) magnets are critical components in the transition to a low-carbon energy economy due to their superior magnetic properties. They have significantly higher rare earth element (REE) content (25-35%) compared to natural resources (0.15-2%), making end-of-life NdFeB magnets a valuable secondary REE source. In this study, the selective recovery of REEs from end-of-life NdFeB magnets was investigated using water leaching following chlorination roasting with NH4Cl. A series of experiments was conducted to evaluate the effect of NH4Cl on the NdFeB magnet ratio, roasting temperatures, and roasting duration. Under optimal conditions (300 degrees C, 3 h, NH4Cl at twice the stoichiometric requirement), the roasted products were subjected to water leaching (500 rpm, 90 degrees C, liquid - solid ratio of 20 mL/g, 1 h). resulting in over 95% REE dissolution. Rare earth oxalates were precipitated from the pregnant leach solution with 90% efficiency using 1.5 times the stoichiometric requirement of oxalic acid. Subsequent calcination at 850 degrees C for 2 h yielded rare earth oxides with 99.8% REE purity. Moreover, the dissolution of iron was effectively suppressed through a simple two-stage Fe(OH)3 precipitation step, providing a more economical and selective recovery route. Les aimants de n & eacute;odyme-fer-bore (NdFeB) sont des composants critiques de la transition vers une & eacute;conomie & eacute;nerg & eacute;tique & agrave; faible carbone gr & acirc;ce & agrave; leurs propri & eacute;t & eacute;s magn & eacute;tiques sup & eacute;rieures. Ils ont une teneur en & eacute;l & eacute;ments de terres rares (ETR) sup & eacute;rieures (25-35%) aux ressources naturelles (0.15-2%), ce qui rend les aimants de NdFeB en fin de vie une source secondaire pr & eacute;cieuse d'ETR. Dans cette & eacute;tude, on a examin & eacute; la r & eacute;cup & eacute;ration s & eacute;lective des ETR des aimants de NdFeB en fin de vie par lixiviation aqueuse apr & egrave;s grillage chlorurant avec du NH4Cl. On a effectu & eacute; une s & eacute;rie d'exp & eacute;riences pour & eacute;valuer l'effet du rapport NH4Cl/aimant de NdFeB, des temp & eacute;ratures et de la dur & eacute;e de grillage. Dans des conditions optimales (300 degrees C, 3 h et une concentration de NH4Cl deux fois sup & eacute;rieure & agrave; la st oe chiom & eacute;trie requise), on a soumis les produits grill & eacute;s & agrave; une lixiviation aqueuse (500 tr/min, 90 degrees C, rapport liquide/solide de 20 mL/g, 1 h) conduisant & agrave; une dissolution de plus de 95% des ETR. On a pr & eacute;cipit & eacute; les oxalates de terres rares & agrave; partir de la solution de lixiviation enrichie avec une efficacit & eacute; de 90% en utilisant 1.5 fois la quantit & eacute; st oe chiom & eacute;trique requise d'acide oxalique. Une calcination ult & eacute;rieure & agrave; 850 degrees C pendant 2 h a produit des oxydes de terres rares d'une puret & eacute; de 99.8%. De plus, la dissolution du fer & eacute;tait efficacement supprim & eacute;e par une simple & eacute;tape de pr & eacute;cipitation de Fe(OH)3 en deux phases, offrant une voie de r & eacute;cup & eacute;ration plus & eacute;conomique et plus s & eacute;lective.

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• MakaleYalnız künye2026/r/gumushane/13718
  Improving the hydrothermal reduced graphene oxide supercapacitor with heat-moisture-treated potato starch as binder

  Daulay, Amru; Yassaroh, Yassaroh; Samada, Lukmanul Hakim; Amrulloh, M. Hanif; Kumaş, Cavit; Nariswari, Mentari Kirana; Putri, Devi Mariska; Chambioso, Yugo

  Alternative binders that can be processed in water are still in the early stages of development for more efficient and sustainable supercapacitors. However, their electrochemical performance is still below average. This study uses heat-moisture-treated starch (starch HMT) as a binder for reduced graphene oxide (rGO) supercapacitors. Starch HMT has been fabricated at 120 °C. The XRD diffractogram exhibits peaks at 2θ angles of 15°, 17°, 22°, and 24°. The 2θ values indicate that potato starch is of type B. FTIR spectra show the formation of OH, C–O–C, C-O, C–O–C, and C-H bonds. SEM images show cracks in the morphology. Electrochemical testing shows a specific capacity of 230 F/g at a current density of 1 A/g. The charge–discharge stability of the electrodes at 5000 cycles is 90%. These results offer a framework for developing electrode materials and binders for supercapacitors.

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• Derleme MakaleYalnız künye2026/r/gumushane/13708
  Activated Carbon Derived from Coal and its Application for Wastewater Treatment

  Daulay, Amru; Yassaroh, Yassaroh; Huda, Miftahul; Sumardi, Slamet; Prasetia, Hendra; Kumaş, Cavit; Yusmiati; Lestari, Devi

  Coal is used to produce fuels, chemicals, and other high-value-added products to improve efficiency. Activated carbon (AC) derived from coal is an important part of coal’s resource utilization and is high-value-added. This study presents relevant research on AC derived from coal, including raw material selection, preparation methods, modification techniques, and regeneration methods. The potential applications of AC derived from coal for the adsorption of contaminants, including heavy metals, pesticides, pharmaceutical compounds, and organic and inorganic compounds, are reviewed. One of the advantages of using AC derived from coal in wastewater treatment is high adsorption, low cost, and sustainability.

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• Derleme MakaleYalnız künye2026/r/gumushane/12275
  Red mud as a source of scandium: A review

  Kumaş, Cavit; Prasetia, Hendra; Astuti, Widi; Sumardi, Slamet; Mufakhir, Fika Rofiek; Fasya, Muhammad Rizki Firdaus

  The residue produced during the extraction of aluminum from bauxite ore via the Bayer process is known as red mud (RM), with 0.5–2.5 t of RM generated for each ton of alumina produced. Due to its highly alkaline nature (pH = 10.0–12.5), RM poses significant environmental threats and requires large storage areas. To address this environmental concern and develop sustainable way to utilize RM, extensive research has been conducted in fields such as soil remediation, metal recovery, steel production, catalytic reactions, cheap adsorbents for pollutant removal, ceramics, brick production, and pigment and slag additives for paint production. While early studies on metal recovery from RM focused on the recovery of metals such as Fe and Al, recent years have seen an increase in research on Sc recovery from RM, as RM is now recognized as an important source for Sc. This review examines in detail methods such as direct acid leaching, bioleaching, acid baking, and water leaching used for Sc recovery from RM. Additionally, data on the recovery of not only Sc but also other metals from RM are presented.

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• MakaleAçık Erişim2023/r/gumushane/11921
  Investigation of geometric object and indoor mapping capacity of Apple iPhone 12 Pro LiDAR

  Günen, Mehmet Akif; Erkan, İlker; Aliyazıcıoğlu, Şener; Kumaş, Cavit

  LiDAR (light detection and ranging) sensors use laser beams to calculate distances in the surroundings. These sensors can be applied to a wide range of tasks, and they are frequently helpful in tasks like building 3D maps, navigating airplanes, robots, conducting mining operations, and automated driving. High-resolution distance measurements are taken by LiDAR sensors, but they also gather environmental data. This information aids in locating, identifying, and quantifying things and their surroundings. The iPhone 12 Pro, which Apple released in 2020, was evaluated for accuracy with various geometric shapes and its capacity to recognize indoor environments. Free of charge 3D Scanner and the Clirio Scan application were employed in this situation. However, it was found that the root mean square error and mean error in indoor mapping were ±1.41 cm and-0.56 cm in 3D Scanner and ±3.94 cm and-0.60 cm in the Clirio Scan application, respectively, despite the findings obtained showing low accuracy in scanning small geometric objects due to the scanning difficulty. Clirio does not reject the null hypothesis in the t-test that was conducted. The accuracy of the LiDAR sensor in indoor mapping has been shown to be more promising than that of small items. In order to evaluate the reliability and reusability of the indoor mapping application according to reference measurements, intraclass correlation test was performed and the results were determined to be reliable.

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• MakaleAçık Erişim2021/r/gumushane/14843
  Effect of heating on structure and leaching characteristics of a zinc carbonate ore

  Kumas, Cavit; Obut, Abdullah

  In this work, the structural changes occurred in a zinc carbonate (smithsonite) ore sample following heating at temperatures between 523 K and 1173 K were investigated in detail using X-ray diffraction (XRD), thermal (TG/DTA) and Fourier-transform infrared (FT-IR) spectroscopy analyses. Afterwards, the leaching characteristics of zinc from the ore sample and the heated ore samples in sodium hydroxide solutions were determined. While heating at 523 K did not cause any structural change in the ore sample, heating at 723 K completely converted smithsonite (ZnCO3) in the ore sample to zinc oxide (ZnO), which resulted lower zinc leaching efficiencies of 40.6% and 62.0% for 3 and 4 mol/dm3 NaOH concentrations, respectively, in comparison to zinc leaching efficiencies (67.2% and 70.7%) obtained for the unheated ore sample. On the other hand, due to neoformation of dissolution resistant ZnFe2O4, Ca2ZnSi2O7 and ZmSiO4 phases during heating and formation of CaZm(OHD2H2O phase during leaching, the leaching efficiency of zinc further decreased to 22.2% and 31.3%, respectively, in 3 and 4 mol/dm3 NaOH solutions for the ore sample heated at 1173 K. The formation of zinc-containing dissolution resistant phases by high-temperature heating was observed to be the only reason for the reduction in the zinc leaching efficiency (49.4% at 1173 K) at the highest NaOH concentration (8 mol/dm3) studied. In this work, the comparative precipitation studies were also conducted and crystalline zinc oxides with different morphologies could be precipitated at considerably high efficiencies from the selected pregnant solutions obtained following leaching.

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• MakaleYalnız künye2016/r/gumushane/18824
  Activated Carbon Production From Hazelnut Shells

  Kumaş, Cavit; Ergül, Burcu; Sayin, Zehra Ebru

  Activated carbon was prepared from hazelnut shell by chemical activation. In practice, activation was provided  K2CO3  and  K2CO3  +  H3BO3  treatment  with  hazelnut  shell.  In  order  to  find  the  optimum activated carbon, different K2CO3 (15 %, 30 % and 45 %) and H3BO3 (3%, 5% and 10%) concentration, activation  temperature  (500,  600,  750,  900°C)  and  carbonization  time  (30,  60  and  120  minute)  was employed. The produced activated carbon samples, moisture content, ash content, carbonization yield, iodine  number,  hardness,  surface  area,  mercury  porosimetry,  SEM  and  adsorption  capacity  were studied  to  determine  the  optimum  sample.  As  a  result  of  studies,  optimum  activated  carbon  was obtained  at  5%  boric  acid  and  30  %  potassium  carbonate  acid  concentration,  900°C  carbonization temperature  and  60  minute  carbonization  time.  The  obtained  iodine  number  of  activated  carbon 1009.71  mg/I2,  surface  area  780.31  m2/g  was  determined.  Also  made  hardness  and  adsorption  tests produced results of high hardness of the active carbon (93.33 %) and was found to have high adsorption capacity.  Due  to  having  low  moisture  and  ash  content  with  high  surface  area,  hardness,  of  hazelnut shell is considered to be a potential raw material for producing activated carbon.

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