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Thermal upgrading is the part of selective reduction process which is for nickel extraction with holding temperature in low (300-500℃) before reduction process. The mixing way of laterite makes them useful for extraction and no bounding in the roasting process which has problem in impurities. The optimum carbon percentage is the concerned purpose for this research. The ratio of saprolite and limonite (solid: solid) are 1:4 and gave heat treatment at 250℃ for 60 minutes and continue to 1150℃ with 1 h holding time and magnetic separation for getting the optimum nickel grade and recovery. All samples are analysed with XRD, XRF, and SEM-EDS to get info on the phases, chemical composition, and morphology. The optimum ratio result based on minimum impurities in the product is 1.5% carbon, with the nickel grade is 2.93 wt.%. [ABSTRACT FROM AUTHOR]

Selective reduction can be applied with thermal upgrading that is the process for nickel extraction with holding temperature in the range 1150℃. The effect and type of reductor are the main factor during the selective reduction process which could control the percentage and grain size of nickel. With those factors, this research will be finding the variation of reductor type. The first step is saprolite and reductor characterization. The percentages of Ni, Fe, Mg, Al, and Si in saprolite are given in 1.82, 30.47, 10-20, 4.86, and 8.1 weight percent. Saprolite has 53.1 percent iron oxide/oxyhydroxide, 38.3 percent lizardite, and 8.7 percent silicate. For reductor, those are graphite, palm kernel shell, and anthracite with carbon percentage 98, 77, and 68. From XRF, the optimum nickel grade is in the graphite and anthracite with 6.5 and 7 wt.%. For phases, the ferronickel is appearing in the high intensity for the optimum reductor type and the microstructure is around 5-10 um for both. Moreover, the optimum reductor type are graphite and anthracite. [ABSTRACT FROM AUTHOR]

Selective reduction of nickel laterite is a pyrometallurgical process using slightly lower temperatures (1100-1200°C) than conventional smelting technology, such as blast furnaces and rotary kiln electric arc furnaces. It is followed by the physical upgrading using a magnetic separation process to deliberate ferronickel from the impurities. In addition, the additive of sodium sulfate is added to increase the nickel recovery. Limiting the addition of reductant can also be carried out to reduce the metallization of iron, thus increasing the nickel grade in ferronickel. Nevertheless, its low nickel recovery due to ferronickel's small particle size is still a significant problem in this selective reduction process for saprolitic nickel ore at low-temperature. In this work, the effect of the mixture of saprolite and limonite in the reduction process on the particle growth of ferronickel will be investigated clearly. The nickel laterite was reduced in a muffle furnace at 1150°C for 60 minutes, followed by a wet magnetic separation process using 500 Gauss of a magnetic field. The XRF was used to identify the iron and nickel in the concentrate and tailings, while the XRD and SEM-EDS were used to analyze the phase transformation along the reduction process and microstructure of the reduced ore. The results showed that the optimal process for limonite and saprolite was generated by adding 0.2 stoichiometry reductant. In the saprolite reduction process, ferronickel's nickel grade is higher, but the recovery is lower than limonite. Mixing saprolite with limonite increased the ferronickel particle size, increasing nickel recovery. Nevertheless, the nickel grade in ferronickel decreased. [ABSTRACT FROM AUTHOR]

The selective reduction process and magnetic separation are the combination processes for separating nickel and iron. This process uses the addition of Na2SO4 and graphite. Those are the optimal of separation process to limit iron oxide because the reductanthas no volatiles. The stoichiometry of graphite plays an essential role because the carbon and energy needed are for the reduction. This experiment studied the effect of stoichiometry on the nickel grade, recovery, and grain size in the variation of graphite stoichiometry of 0.125, 1,and 1.5 with a reduction temperature of 1150 °C for 60 minutes and 10 % Na2SO4. XRD and XRF examined the mineralogical composition of the raw and reduced samples. The microstructure was analyzed by an optical microscope. The optimum result is in the 0.125 stoichiometry with nickel grade and recovery of 4.94 wt% and 86.18% and the grain size is large due to the amount of carbon is high. [ABSTRACT FROM AUTHOR]

The effect of reductant (tannic acid) residue on manganese precipitation from pregnant leach solution was studied using batch and titration methods. Potassium permanganate and sodium hypochlorite were employed as oxidants for manganese precipitation. The results demonstrated that divalent manganese precipitation was mainly affected by initial pH, tannic acid concentration and molar ratio. Among these, initial pH played a significant role in determining the possible reaction during the precipitation process, which was discerned and discussed based on batch and titration experiment (electrochemistry) results. The studies also demonstrated that weakly acidic until neutral condition was favorable for the manganese precipitation. In this pH condition, tannic acid oxidation was discouraged. The optimum pH for manganese precipitation using potassium permanganate and sodium hypochlorite were 5 and 7, respectively. [ABSTRACT FROM AUTHOR]

In this study, the quaternary basicity (CaO+MgO/Al2O3+SiO2) with modified MgO and CaO content in the selective reduction of limonitic nickel ore was investigated clearly. Limonitic nickel ore used in the process contains 1.38% Ni and 38.2% Fe. The anthracite coal and 10 wt% of Na2SO4 were used as reductants and additives, respectively. The reduction process conducted at 1150°C for an hour continued with the magnetic separation process to separate concentrate/ferronickel and tailing/impurities. The higher basicity with modified MgO resulted in lower nickel grade due to the formation of more magnesium silicate/forsterite, which could inhibit metal oxide reduction. The 0.3 of basicities with modified CaO addition showed the optimum condition due to its ability to break the silicate structure. [ABSTRACT FROM AUTHOR]

Kinetic leaching on recovery of cobalt (Co) and lithium (Li) from spent lithium-ion battery (LIB) cathode using tannic acid-acetic acid as leaching agent was carried out to discern the leaching mechanism in terms of acid concentration and temperature. Three kinetic models, i.e. shrinking core model (SCM) chemical reaction and product layer diffusion and shrinking particle model (SPM) film diffusion was employed to perceive the possible mechanism of Co and Li dissolution. Fitting experimental data using the models revealed that increasing acetic acid concentration caused the dissolution mechanism to follow SCM product layer diffusion. This was probably due to the molar ratio of acetic acid to Co was not sufficient to control the passivation of the Co(OH)2 product layer. In the case of tannic acid, increasing concentration obeyed SPM film diffusion model. Due to excess concentration of tannic acid in the liquid phase, dissolution was more influenced by the reduction rate of Co by tannic acid on the solid-liquid interface rather than mass transfer through the boundary layer (insoluble layer). Dissolution of Co and Li at elevating temperature obeyed SCM product layer diffusion, indicating higher temperature encourages the reduction rate to produce Co(OH)2 passivation layer. Still, at the same time, increasing temperature boosted ion movement and encouraged the diffusion through product layer. Activation energy (Ea) calculation yielded 5.53 kJ/mol and 26.8 kJ/mol for Co at 30-60 °C and 60-80 °C, respectively, while Li was 21.51 kJ/mol. Relatively low Ea (< 40 kJ/mol) indicated the physical interaction was more prominent than chemical reaction control. The plot between rate constant and reactant concentration showed that the effect of tannic acid and acetic acid concentration was significant for Co dissolution rate (order 0.927 and 0.638 for tannic acid and acetic acid concentration). For Li, the reaction order was 0.451 for tannic acid and 0.021 for acetic acid concentration, implying less influence of reactant concentration on Li dissolution. Although Li dissolution was less affected by reactant conditions, the recovery of Li and Co was almost identical in each experiment, which suggested the Li dissolution was controlled by Co dissolution through product layer passivation. [ABSTRACT FROM AUTHOR]

The selective reduction of nickel and adequate growth of ferronickel grains is imperative for efficient preparation of ferronickel from nickeliferous laterite ore via the process of direct reduction followed by magnetic separation. The reduction behaviours of a saprolite laterite ore in the presence of sodium sulphate were investigated, with an emphasis on thermodynamic analysis, selective reduction ratios and kinetics. To separate the interactions between Ni and Fe, chemical titration analysis was adopted to determine the contents of various Ni and Fe species in the roasted pellets and a modified equation to assay metallic iron content. This process uses the addition of sodium sulphate as the additive and graphite as the reductant. The additive and reductant are the optimal n the separation process to limit the form of iron oxide. The Na2SO4 dosage plays an important role in the process that causes its behaviour to reduce the growth of iron oxide. In this experiment, the study effect of Na2SO4 dosage with graphite as a reductant on the nickel grade, recovery and grain size of iron-nickel has been investigated in the variation of Na2SO4 dosage of 5, 10, and 15 % with reduction temperature 1150 °C for 60 minutes and the reductant stoichiometry is 0.125 from equilibrium condition is equal 0.63 gram. The mineralogical composition of the raw and reduced samples was analysed by XRD, AAS, and XRF. The grain size was measured with an optical microscope. The optimum Na2SO4 dosage is 15 %, which produces a concentrate with nickel grade, and the recoveries are 5.65 wt.% and 30.33 % when the grain size is greater than the high level of dosage because the liquid phase provides access for the transfer of metal ions and then prompts the growth of ferronickel grains. [ABSTRACT FROM AUTHOR]

Material Ni-Hard 2 which was used in this experiment has the composition 2.9 wt.% C; 3.3-4.8 wt.% Ni; and 1.5-2.6 wt.% Cr. Material Ni-Hard 2 has lower wear-resistant than the other Ni-Hard. Material Ni-Hard 2 was alloyed with the vanadium to improve the physical properties by melting them with the variation of composition vanadium (3 and 7 wt.%) in the induction furnace and was formed to the desired shape for each test. Phase structure after alloying is austenite, carbide, martensite, and ferrite according to XRD result and microstructure analysis. The optimum hardness is in the 7 wt.% of vanadium that is 43.6 HRC. For the impact was influenced by the changing of microstructure due to the variation of composition and the optimum impact is in the 3 wt.% vanadium that is 73.3 J/cm². Whereas the optimum wear rates of after alloying is in the 3 wt.% vanadium that is 50 x 10-8 mm³/mm. The effect of composition variation of vanadium could reduce the grain size, impact, and wear-resistant due to the low content of ferrite is in the microstructure. On the other hand, the hardness could increase. [ABSTRACT FROM AUTHOR]

Investigation of Averrhoa bilimbii as bioleaching agent was carried out. Parameters of leaching duration, acid concentration, and temperature were performed in iron removal process. Feldspar with sized 149 μm was diluted in 30 ml acid solution in order to reduce its iron content. The experimental results showed a good technical feasibility of the process which iron oxide content of feldspar was decreased from 2.24% to 0.29%. The lowest iron concentration remained was obtained after 5 hours of leaching treatment at 60 °C, and concentrated (100 vol%) Averrhoa bilimbii extract as bioleaching agent. SEM characterizations were carried out on the feldspar before and after the leaching treatment. The result shows that there were no significant effect of leaching process on the ore morphology. [ABSTRACT FROM AUTHOR]