Ni Grade Research Articles

The Geology, Geochemistry, and Mineralogy of the Moa Bay Ni Laterite Mining District, Cuba

Abstract The Moa Bay lateritic Ni-Co mining district (eastern Cuba) has total mineral resources of 198.54 million metric tonnes (Mt) at 1.07% Ni and 0.12% Co. Laterite profiles from this district are characterized by their oxide-dominated ore zones. Laterite profiles from the Yagrumaje Norte, Punta Gorda, and Yamanigüey deposits contain average Ni and Co concentrations in the oxide zone of 0.88 and 0.12%. Goethite is the most abundant mineral in the oxide zone and the most important Ni-Co-Sc–bearing mineral, with median NiO, CoO, and Sc contents of 0.78 wt %, 0.07 wt %, and 58 ppm, respectively, and up to 2.77 wt %, 0.26 wt %, and 117 ppm. Maghemite is also widely present (avg of 5% and up to 19% modal proportion) and represents an important but largely ignored Ni- and Co-bearing ore phase, with median NiO and CoO concentrations of 2.11 and 0.25 wt %, respectively, and maximum values of 13.9 and 1.84 wt % each. Nickel and Co substitute for ferric iron in the structure of maghemite. Manganese oxyhydroxides (lithiophorite and lithiophorite-asbolane intermediate), which are also significant Ni-Co–bearing phases, have median NiO and CoO contents of 10.6 and 6.41 wt %, respectively. Some Mn oxyhydroxides, which formed after replacing goethite, also contain significant amounts of Sc (up to 94 ppm). Although most deposits in the Moa Bay lateritic district are classified as oxide type, Yamanigüey (avg Ni grade of 1.98%) is characterized by well-developed saprolite horizons, with secondary serpentine (serpentine II) and garnierite being the main Ni-bearing phases.

Comparative Analysis of Mixing High Grade Limonite and Low Grade Saprolite Nickel Ore to Meet Market Demand at PT Mandiri Mineral Perkasa

PT Mandiri Mineral Perkasa is a contractor company operating in the field of nickel mining and has fulfilled the market/smelter demand requirements for Ni 1.5% - 2.0%, by setting a Cut Of Grade (COG) collection limit of Ni 1.4%. The aim of this research is to determine the Ni content of high grade limonite and low grade saprolite at the research location, and to determine the Ni content of high grade limonite and low grade saprolite, and to determine the additional tonnage and levels to meet market demand. In this study, the blending method was used, a mixing process between different low grade and high grade nickel ores to obtain appropriate mixture results, so that from the results of blending/mixing high grade limonite nickel ore, Ni 1.43 and Fe 26.71% were obtained, and for low grade saprolite you get 1.59% Ni and 26.73% Fe, for the results of blending/mixing high grade limonite and low grade saprolite you get 1.51% Ni and 26.72% Fe, efforts can be made to meet demand Ni 1.8% market with 5,000 tons needs to increase the grade and tonnage, namely, Ni grade 2.32% and 2,111.45 tons.

Nickel Grade Inversion of Lateritic Nickel Ore Using WorldView-3 Data Incorporating Geospatial Location Information: A Case Study of North Konawe, Indonesia

The North Konawe region in Indonesia, known for its lateritic nickel (Ni) deposits, holds significant potential for obtaining Ni resources. However, the complex topographic conditions of this area pose challenges. Exploring the application of remote sensing technology to reveal the spectral response mechanism of Ni grade from high-precision multispectral data and inversion of Ni grade represents a novel direction in future Ni resource exploration. Traditional remote sensing inversion methods solely consider the spectral characteristics of sample data and ignore vital geospatial location information. As a result, efficiently obtaining regional details of target substance content over large areas has become challenging. The introduction of the geographically weighted regression (GWR) method offers an opportunity for fine-grained Ni grade inversion based on remote sensing. This study focused on the E and K blocks within the lateritic Ni mining area in North Konawe. Through utilizing the WordView-3 multispectral data which exhibits immense potential in quantitative remote sensing inversion studies, GWR was employed to integrate spectral features and spatial information. The goal was to reveal the correlation between multispectral remote sensing data and Ni grade. The obtained results were then compared and analyzed with multiple linear regression (MLR) and back propagation neural network (BPNN) models. The findings revealed that GWR achieved the highest coefficient of determination R2 of 0.96, surpassing MLR and BPNN values of 0.05 and 0.17, respectively. Additionally, GWR exhibited the lowest root mean square error of 0.04, which was lower than those of MLR and BPNN with the values of 0.25 and 0.23, respectively. These results confirmed the enhanced stability and accuracy of the GWR method compared to MLR and BPNN. Furthermore, GWR effectively mapped the spatial distribution trends of Ni grades in the study area, providing evidence of the method’s effectiveness in Ni grade inversion. The study also delved into the inversion effect of the GWR method in areas with varying weathering crust thickness and vegetation cover. The research revealed that higher values of weathering crust thickness negatively impacted the inversion effect. However, the influence mechanism of vegetation cover on Ni grade inversion necessitated further investigation. These results served as a significant demonstration of the remote sensing inversion of mineral resource grades in similar areas. They provided valuable insights for future exploration and decision-making processes.

Efficient Utilization of Limonite Nickel Laterite to Prepare Ferronickel by the Selective Reduction Smelting Process

Ferronickel products obtained from the traditional process used to treat limonite nickel laterite usually assay very low-grade Ni, only 3–5% Ni due to the high Fe/Ni ratio of limonite nickel laterite. This paper describes an investigation conducted to upgrade limonite nickel laterites for the preparation of ferronickel by using selective reduction smelting technology. By means of thermodynamic calculations and smelting experiments, the smelting separation mechanism and the behavior of P and S removal in the smelting process, as well as the influence of smelting factors, have been systematically identified. The best production index of ferronickel is obtained under optimized conditions as follows: smelting the pre-reduced lumps at 1525 °C for 45 min with a basicity of 0.60, MgO/SiO2 ratio of 0.30, and nickel and iron metallization rate of 94.30% and 10.93%, respectively. The resulting ferronickel features a nickel and iron grade of 12.55% and 84.61% and a nickel and iron recovery of 85.65% and 10.87%, respectively. In addition, the content of S and P contained in ferronickel is only 0.11% and 0.0035%, respectively. The ferronickel obtained from the selective reduction smelting process is a fine material for the subsequent stainless steel smelting due to its high Ni grade and low content of impurities.

PGE geochemical and Os-S-Sr-Nd isotopic constraints on the genesis of the Shitoukengde magmatic sulfide deposit in the East Kunlun Orogenic Belt, NW China

Numerous early Paleozoic mafic–ultramafic intrusions that host important Ni-Cu sulfide mineralization occur in the northern part of the Qinghai-Tibet Plateau, NW China. The sulfide-bearing Shitoukengde Ni-Cu deposit, which is hosted in a ∼424 Ma mafic–ultramafic intrusion, is one of the most represent magmatic sulfide deposits in the East Kunlun Orogenic Belt. The intrusion is composed of a large gabbroic body, cut by lherzolite, olivine websterite, websterite, and minor dunite. Disseminated and net-textured sulfide mineralization occurs as lenses in the center and towards the bottom of the ultramafic bodies. The sulfide mineralization has variable sulfur contents of 0.3 to 13.6 wt% with Ni grade of 0.41 wt% on average, and low platinum-group element (PGE) concentrations (<8.2 ppb Ru and <11.9 ppb Pd). Pd and Ru tenors of bulk sulfides in the deposit are characterized by a positive correlation, indicating that PGE tenor variations are mainly controlled by varying R-factors (magma/sulfide mass ratio). The estimated PGE concentrations in the Shitoukengde magma are about three orders of magnitude lower than those in continental tholeiites. The significant PGE depletions in the Shitoukengde deposit may be due to sulfide removal in the magma conduit at depth. Our new sulfur isotope data reported range in δ34S values from −5.0 to 4.9‰ for the sulfide minerals of the Shitoukengde deposit, clearly distinct from those of mantle-derived sulfur (0 ± 2‰) and immediate country rocks (1.1 to 2.0‰). This, together with the modeling for S isotope variation as a function of R-factor, suggest that the current δ34S range is attributed to the addition of external sulfides with anomalous δ34S into the magma at depth, followed by progressive modification to crustal signature by uncontaminated pulses of magma. The ultramafic rocks exhibit low εNd(t) values (−4.71 to 2.12) and high (87Sr/86Sr)i ratios (0.7073 to 0.7130), which are more enriched relative to the isotopic compositions of depleted mantle. Mixing calculations indicate that about 15 to 20 wt% of lower crustal contamination plus variable upper crustal contamination is required to explain the variations of Sr-Nd isotopes in the Shitoukengde intrusion. Significant crustal contamination is also supported by the mineralization at Shitoukengde having high (187Os/188Os)i (0.24 to 4.51) and γOs(t) values (0.24 to 2534) that are comparable to or higher than those of the important Ni-Cu deposits worldwide. Current results provide evidence that assimilation of crustal sulfur at deep crust and siliceous material with variable crustal contamination during magma ascent and emplacement played critical roles in the attainment of sulfide saturation in the parental magma and the formation of the Shitoukengde deposit.

Interobserver Reliability of the Nancy Index for Ulcerative Colitis: An Assessment of the Practicability and Ease of Use in a Single-Centre Real-World Setting.

Histological disease severity assessment in ulcerative colitis [UC] has become a mainstay in the definition of clinical endpoints ['histological remission'] in clinical trials of UC. Several scores have been established in the microscopic assessment of disease activity, but the Nancy index [NI] stands out as being the histological index with the fewest scoring items. To what extent histological assessment using the NI is affected by interobserver reliability in a real-word setting is poorly understood. We therefore performed a single-centre retrospective analysis of NI assessment in patients with UC. We retrospectively evaluated the NI in two independent cohorts [total: 1085 biopsies, 547 UC patients] of clinically diagnosed UC patients, who underwent colonoscopy between 2007 and 2020. Cohort #1 consisted of 637 biopsies from 312 patients, while Cohort #2 consisted of 448 biopsies from 235 patients. Two blinded pathologists with different levels of expertise scored all biopsies from each cohort. A consensus conference was held for cases with discrepant scoring results. Finally, an overall consensus scoring was obtained from both cohorts. The interobserver agreement of the NI was substantial after the assessment of 1085 biopsy samples (κ = 0.796 [95% confidence interval, CI: 0.771-0.820]). An improvement of the interobserver agreement was found with increasing numbers of samples evaluated by both observers (Cohort #1: κ = 0.772 [95% CI: 0.739-0.805]; Cohort #2: κ = 0.829 [95% CI: 0.793-0.864]). Interobserver discordance was highest in NI grade 1 [observer 1: n = 128; observer 2: n = 236]. Interobserver discordance was lowest in NI grades 0 [observer 1: n = 504; observer 2: n = 479] and 3 [observer 1: n = 71; observer 2: n = 66]. The NI is an easy-to-use index with high interobserver reliability for assessment of the histological disease activity of UC patients in a real-world setting. While NI grades 0 and 3 had a high level of agreement between observers, NI grade 1 had a poorer level of agreement. This highlights the clinical need to specify histological characteristics leading to NI grade 1.

ANALISYS OF THE FRACTURE THOUGHNESS IN THE HEAT AFFECTED ZONE (HAZ) OF ONE HSLA STEEL

The original contribution of the experimental research described here is intended to ensure that the KIC fracture toughness in the heat affected zone (HAZ) of USITEN 355 0.5 Ni Grade 1 steel produces a CTOD (?) (Crack Tip Opening Displacement) within the standard values, making the steel compatible with the welding procedure used and the heat energy supplied, which is 2 kJ/mm, in order to confirm that the grain size braking mechanism carried out by the microalloying agents (V, Nb, Al) of the base metal are working as intended. A further aim is to ensure, as far as possible, a correlation between the welding parameters and the results obtained from the fracture tests, in such a way that, should the results of the tests be unsatisfactory, the appropriate solution can be applied to the weld so that the parameters that govern the fracture tests are acceptable. The work developed here is useful as a guide and reference for future research on fracture mechanics in microalloyed steels. Keywords: HSLA, Fracture toughness, CTOD, HAZ, heat input energy, SMAW

MICRO-CRACK ANALYSIS IN THE STUDY OF FATIGUE FRACTURE IN THE HAZ IN THE HIGH YIELD STRENGTH MICRO-ALLOYED STEELS

Various applications have been described in the literature for the High-Strength and Low-Alloy steels (HSLA) industry, analysing their use both in industrial and marine equipment and machines and in structures that require appropriate resilience values and toughness at low temperatures. For successful operation under conditions as large structures under extreme service conditions, it is essential to ensure the proper toughness both in base metal (USITEN 355 0.5 Ni Grade I steel) and in the heat-affected area of the weld. (ZAC). This research carries out Crack Tip Opening Displacement (CTOD) tests, showing, in this article, the first part of the test corresponding to fatigue pre-cracking and a summary table of the results of fracture toughness, to guarantee that, under the conditions which exist in welding, both the fatigue fracture values and the fracture toughness are acceptable by the applicable standards. Keywords: SMAW, weld line, CTOD, stress intensity factor, input heat energy, crack growth rate, fatigue fracture, fracture toughness

Recovery of nickel and preparation of ferronickel alloy from spent petroleum catalyst via cooperative smelting–vitrification process with coal fly ash

ABSTRACT Spent petroleum catalyst (SPC) is a highly toxic material since it contains heavy metals and hazardous substances. A novel recycling technology based on the cooperative smelting–vitrification process by using coal fly ash (CFA) as a fluxing material was proposed. The benefits of employing CFA in this cooperative smelting–vitrification process of SPC have been demonstrated via the results of lab-scale and scale-up experiments. The experimental results indicated that with a collector iron (Fe) addition of 26 wt%, a C/O molar ration of 1.4, and an H3BO3 addition of 14 wt%, the maximum nickel (Ni) recovery was ∼98% by controlling the CFA addition of 40–50 wt%, basicity of 0.4–0.5, smelting temperature of 1550°C, and smelting time of 60 min, respectively. In this process, a ferronickel (Ni–Fe) alloy with a high Ni grade of 10 wt% was successfully obtained, which could be directly further produced stainless steel. Meanwhile, a glass slag with a low Ni content (below 0.12 wt%) was also obtained, and its leaching characteristics further confirmed it is a non-hazardous slag because heavy metals were successfully encapsulated in glass slag, and thereby, this proposed method achieved the transformation from hazardous solid waste to general solid waste. The results of the 10 kg scale-up experiment indicated the possibility of industrialization of this new technology. Therefore, the process proposed in this study is a practical and promising process for Ni recovery from SPC and reutilization of CFA.

Gypsum utilization on selective reduction of limonitic laterite nickel

The world's nickel demand is increasing, especially with more countries starting to produce battery-based electric vehicles. Currently, nickel is the main element used for the fabrication of Nickel Manganese Cobalt (NMC) batteries. Nickel itself can be extracted from its ore through pyrometallurgical route. Selective reduction of nickel using a selective reducing agent is needed in order to produce nickel with appropriate grade. This study aims to study the possibility of gypsum as a selective reducing agent in the direct reduction process. In this process, laterite nickel ores with nickel content of 1.59% were crushed and classified until the feed particle size was smaller than 50 standard mesh. The crushed laterite nickel ores were then mixed with gypsum and a binder material to undergo briquetting and drying. A bed mix composed of limestone powder and coal was added into the crucible alongside the ore briquettes. Carbothermic reduction was done at 1400 °C for 6 h. The product was then crushed and separated through magnetic separation. The reduced product's chemical composition was analyzed using Scanning Electron Microscope-Energy Dispersive X-Ray and X-Ray Diffractometer. The results indicate that gypsum can provide a selective effect on the direct reduction process of laterite nickel ore. A selective effect that lowers the grade of iron can occur due to the formation of iron sulfides. The use of 12% gypsum was able to produce a product with Ni grade of 4.13%, Ni recovery of 91.81%, and selectivity factor of 5.72. Therefore, based on the results of this experiment, gypsum minerals can be used as a potential low-cost alternative as an additive for nickel selective reduction.

Effect of tribo-layer on the corrosion behavior of WC-Co and WC-Ni cemented carbides in synthetic mine water

For rock drilling applications, the cemented carbides containing hard WC grains in a ductile Co binder are commonly used as drill buttons. In considering the environmental and health aspects an alternate to Co-binder is pursued. In the present work, using standard scratch testing the friction and wear properties of the WC-20 vol% Ni grade is studied and compared to that of WC-20 vol% Co grade. The deformation and wear characteristics of the cemented carbide grades are evaluated and correlated to the microstructural changes during scratch testing. Also, the electrochemical impedance spectroscopy (EIS) behavior of the as-polished and scratch-tested cemented carbides was studied at the open circuit potential condition of simulated mine water (SMW) for 1 h. The obtained polarization resistance and charge transfer resistance values from the EIS analysis are correlated to the corrosion resistance of the samples. In both as-polished and scratch-tested conditions the WC-Ni grade exhibited higher polarization resistance values indicating high corrosion resistance than the WC-Co. In comparison to the as-polished sample, both the scratch-tested cemented carbides exhibited higher corrosion activity in particular within the scratch-induced tribo-layer. Severe corrosion and complete removal of the tribo-layer was observed for the WC-Co grade when exposed to SMW for 15 h. Site-specific scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX) analysis were carried out to get insight into the corrosion behavior of as-polished and scratch-tested cemented carbides.

The influence of distance weight on the inverse distance weighted method for ore-grade estimation

In order to study the influence of distance weight on ore-grade estimation, the inverse distance weighted (IDW) is used to estimate the Ni grade and MgO grade of serpentinite ore based on a three-dimensional ore body model and related block models. Manhattan distance, Euclidean distance, Chebyshev distance, and multiple forms of the Minkowski distance are used to calculate distance weight of IDW. Results show that using the Minkowski distance for the distance weight calculation is feasible. The law of the estimated results along with the distance weight is given. The study expands the distance weight calculation method in the IDW method, and a new method for improving estimation accuracy is given. Researchers can choose different weight calculation methods according to their needs. In this study, the estimated effect is best when the power of the Minkowski distance is 3 for a 10 m × 10 m × 10 m block model. For a 20 m × 20 m × 20 m block model, the estimated effect is best when the power of the Minkowski distance is 9.

Modeling and Resource Classification Lateritic Nickel Deposits on a Heterogeneous Block in The Haul-Sagu Area using Estimation and Simulation Geostatistical Method

Deposits modeling is a very important thing in the exploration field, especially in estimating reserves. This research was conducted to model the geometry of lateritic nickel ore deposition on heterogeneous blocks using the geostatistical estimation method Ordinary kriging (OK) and simulation methods namely, Sequential Gaussian Simulation (SGS) then the distribution of laterite zonation was carried out to calculate the resource and mineral resource classification based on estimation data and simulation. The estimation results using the OK method have an average value of Ni higher than the average Ni grade from the SGS simulation results. Analysis of the calculation of total tonnage of resources from the estimated OK data shows the total amount of measured tonnage of 5,875 tons is far lower than the amount of resource tonnage from the SGS simulation data which displays the total amount of tonnage measured 189,766 tons. However the average grade of Ni from measured OK Resources is 1.49% higher, compared to the average Ni grades from measured resources of SGS 1.33%. with a difference of 0.16% Ni grades. The opposite occurs when the average Fe grade of the measured OK resource is lower 24.15% compared to the average Fe grade of the Measured resource of SGS 32.81% with a very large difference in Fe grade of 8.66%.

Parent rock and climatic evolution control on the genesis of Ni-bearing clays in Ni-Co laterites: New inferences from the Wingellina deposit (Western Australia)

Oxide-type Ni-laterites seldom contain significant Ni-phyllosilicates reserves. This study is focused on the mineralogy of Ni-clays mainly occurring in the saprolite zone of the Wingellina oxide-type Ni-Co laterite deposit. Despite most of the Wingellina reserves occur in the oxide zone, the deposit also has a well-developed high Ni grade saprolite horizon. This study presents a mineralogical and chemical characterization of the Ni-phyllosilicates of the Wingellina saprolite ore, aimed to understand the role of diverse bedrocks (gabbro and serpentinite) and the influence of climate on the formation of different clay types.The main phyllosilicate in the gabbro-derived saprolite consists of dioctahedral Al- and Ni-montmorillonite, originated from the weathering of pyroxene. The genesis of Al- and Ni-rich montmorillonite from pyroxene can be explained by an open system alterative process, in which Al mainly derives from the dissolution of plagioclase. In the serpentinite-derived saprolite, the alteration pathway followed a multistage evolution: (i) lateritic alteration of serpentine I into Ni-serpentine II and tri- and dioctahedral smectites (saponite and nontronite); (ii) late precipitation of interstratified Ni-clays (chlorite-smectite and talc-smectite) as a replacement of former phyllosilicates and as neoformed minerals. The latest phenomenon may be related to the late Miocene shift from humid-and-acid (tropical climate) to saline-and-alkaline conditions (arid to semi-arid climate), and represents an example of post-lateritization processes, rarely observed in laterites located on stable cratons.The aridity-driven precipitation of Ni-rich interstratified clays in the Wingellina laterite can be seen as a new model for explaining the evolution of Ni-laterites in stable cratonic settings experiencing post-lateritization aridity.

Carbothermic reduction of low-grade laterite-graphite composite pellets

The appropriate carbothermic reduction parameters of low-grade laterite-graphite pellets and the influence of calcined temperature on these for upgrading the nickel (Ni) content in pellets were evaluated. Afterward, the impact of the additive (Na2SO4) on Ni grade and Ni recovery of calcined pellets at optimal reduction conditions was also investigated. XRD analysis, thermodynamic calculation, isothermal reduction experiment, BET-specific surface area analysis, bromine methyl alcohol solution analysis, and chemical composition analysis were used in order to obtain the associated parameters. In this study, it showed the improvement of Ni grade and Ni recovery rate of 673 K-calcined laterite-graphite pellets can respectively reach &gt; 30 mass % and 90.2 mass % under the conditions of reduction temperature = 1373 K, reduction time = 30 min, and the mole ratio of fixed carbon to reducible oxygen of iron and nickel in laterite nickel ore (C/O) = 0.6. The reasons were proposed that the 673 K-calcined laterite ores have the highest specific surface area of 46.8 m2/g with pores in the size of 29.7 Å to provide faster Ni reduction at the initial stage followed by reduction. The addition of 5 mass % additive resulted in the best Ni grade of &gt; 30 mass % and the best Ni recovery rate of 93.8 mass % in pellets at the same reduction temperature, time and (C/O) molar ratio.

Weathering of Ophiolite Remnant and Formation of Ni Laterite in a Strong Uplifted Tectonic Region (Yuanjiang, Southwest China)

The Yuanjiang Ni deposit in southwestern margin of the Yunnan Plateau is the only economically important lateritic Ni deposit in China. It contains 21.2 Mt ore with an average grade of 1.05 wt % Ni and has been recognized as the second largest Ni producer in China following the Jinchuan super-large magmatic Ni–Cu deposit. This Ni deposit is hosted within the lateritic regolith derived from serpentinite within the regional Paleo-Tethyan Ophiolite remnants. Local landscape controls the distribution of the Ni mineralized regolith, and spatially it is characterized by developing on several stepped planation surfaces. Three types of lateritic Ni ores are identified based on Ni-hosting minerals, namely oxide ore, oxide-silicate mixed ore and silicate ore. In the dominant silicate ore, two phyllosilicate minerals (serpentine and talc) are the Ni-host minerals. Their Ni compositions, however, are remarkably different. Serpentine (0.34–1.2 wt % Ni) has a higher Ni concentration than talc (0.18–0.26 wt % Ni), indicating that the serpentine is more significantly enriched in Ni during weathering process compared to talc. This explains why talc veining reduces Ni grade. The geochemical index (S/SAF value = 0.33–0.81, UMIA values = 17–60) indicates that the serpentinite-derived regolith has experienced, at least, weak to moderate lateritization. Based on several lines of paleoclimate evidence, the history of lateritization at Yuanjiang area probably dates to the Oligocene-Miocene boundary and has extended to the present. With a hydrology-controlled lateritization process ongoing, continuous operation of Ni migration from the serpentinite-forming minerals to weathered minerals (goethite and serpentine) gave rise to the development of three types of Ni ore in the regolith. Notably, the formation and preservation of the Yuanjiang lateritic Ni deposit has been strongly impacted by regional multi-staged tectonic uplift during the development of Yunnan Plateau. This active tectonic setting has promoted weathering of serpentinite and supergene Ni enrichment, but is also responsible for its partial erosion.

Magnetic separation of pentlandite from serpentine by selective magnetic coating

In this study, pentlandite was selectively separated from serpentine using magnetic coating technology by adjusting and optimizing pH, stirring speeds, magnetic field intensities, and dosages of sodium hexametaphosphate (SHMP) and sodium oleate (SO). A magnetic concentrate with Ni grade of 20.8% and Ni recovery of 80.5% was attained under the optimized operating conditions. Considering the above, the adsorption behaviors of SHMP and SO and the surface properties of minerals after the magnetic coating were studied by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results show that magnetite was preferentially coated on the pentlandite surfaces and sparingly coated on the serpentine surfaces in the presence of SHMP and SO. Furthermore, calculations by Derjaguin-Landau-Verwey-Overbeek (DLVO) theory indicate that the preferential adsorption of magnetite on the pentlandite surfaces is due to the presence of a hydrophobic interaction between the magnetite and pentlandite, which is much stronger than the interaction between magnetite and serpentine.

Genesis of the Permian Kemozibayi sulfide-bearing mafic-ultramafic intrusion in Altay, NW China: Evidence from zircon geochronology, Hf and O isotopes and mineral chemistry

The recently discovered Kemozibayi mafic-ultramafic intrusion and its associated magmatic Cu-Ni sulfide deposits are located at the southern margin of the Chinese Altai Mountain, Central Asian Orogenic Belt in north Xinjiang, NW China. The intrusion is composed of olivine websterite, norite, gabbro and diorite. Disseminated and net-textured Ni-Cu sulfide ores are hosted in the center of the gabbro. In this work, new zircon U-Pb ages, Hf-O isotopic and sulfide S isotopic data, and whole rock and mineral chemical analyses are combined in order to elucidate the characteristics of the mantle source, nature of subduction processes, degree of crustal contamination, geodynamic setting of bimodal magmatism in the region, and the metallogenic potential of economic Cu-Ni sulfide deposit at depth. SIMS zircon U-Pb dating of the gabbro yields Permian ages (278.3±1.9Ma), coeval with the Kalatongke Cu-Ni deposit and with Cu-Ni deposits in the Eastern Tianshan and Beishan areas. Several lines of evidence (positive εHf(t) from +7.1 to +13.3, Al2O3, TiO2 and SiO2 contents in clinopyroxene from olivine websterite, high whole rock TiO2 contents) suggest that the primary magma of the Kemozibayi intrusion was a calc-alkaline basaltic magma derived from depleted mantle, and that the degree of partial melting in the magma source was high. The evolution of the Kemozibayi mafic-ultramafic complex was strongly controlled by fractional crystallization and the crystallization sequence was olivine websterite, norite, and then gabbro. This is evidenced by whole rock Fe2O3 contents that are positively correlated with MgO and negatively correlated with Al2O3, CaO and Na2O, similar LREE enrichment and negative Nb, Ta, Hf anomalies in chondrite and primitive mantle-normalized patterns, and a decrease in total REE and trace elements contents and magnetite content from gabbro through to norite and olivine websterite. Varied and low εHf(t) (+7.1 to +13.3) and high δ18O values (+6.4‰ to +7.2‰) in zircon, high La/Ba, and Rb/Y ratios, and low Nb/La ratios in whole rock samples, suggest 5–10% contamination by subduction related fluid and 10–15% contribution from an upper crustal component. The clinopyroxene TiO2 and Alz values (percentage of tetrahedral sites occupied by Al) in the Kemozibayi intrusion show characteristics of rift cumulate rocks, but minor arc cumulate features, indicating that the mantle source might have experienced a lower degree of subduction metasomatism. A high degree of partial melting of the depleted mantle and subducted oceanic sediments with related fluid metasomatism and crustal contamination in the Kemozibayi mafic-ultramafic intrusion are appropriate for the formation of an economic copper and nickel sulfide deposit. Crustal contamination, crustal S addition and early fractionation of olivine and sulfide induced S saturation and the formation of immiscible sulfide in the Kemozibayi intrusion. With no obvious olivine and Ni-rich sulfide co-crystallization, the Cu grade in the present orebody is higher than the Ni grade, and the proportion of mafic rocks is high in the Kemozibayi mafic-ultramafic complex. Cumulatively, these features suggest that the mafic-ultramafic intrusion underwent early olivine and Ni sulfide segregation, and that deeper or extended portions of the present intrusive body may host Ni mineralization.

Effect of acetic acid on corrosion behavior of AISI 201, 304 and 430 stainless steels

AbstractAustenitic stainless steels are often used to handle organic acids such as acetic acid (CH3COOH), which are extensively used in food contact applications and chemical industries for manufacturing medicines, nutrition and various chemical amalgams. In the present investigation an attempt has been made to compare the corrosion behavior of Cr–Ni (AISI type 304), Cr–Mn–Ni (type 201) and Cr (type 430) stainless steel for economical replacement of higher cost Cr–Ni grade. Immersion testing was performed at room temperature and boiling temperature in acetic acid. Atomic absorption spectroscopy was carried out to evaluate metal ion concentration in the immersion solution. The surface morphology of pit formation was characterized using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. The effect of elemental leaching on electrical conductivity of the immersion solution was evaluated and correlated with pH measurements. A new mechanism has been proposed for the pit formation due to manganese sulfide inclusions. The replacement compatibility was further confirmed with anodic polarization testing and a successful replacement was established for room temperature applications.

Use of centrifugal-gravity concentration for rejection of talc and recovery improvement in base-metal flotation

The possibility of using a centrifugal-gravity concentrator to reject Mg-bearing minerals and minimize metal losses in the flotation of base metals was evaluated. Sample characterization, batch scoping tests, pilot-scale tests, and regrind-flotation tests were conducted on a Ni flotation tailings stream. Batch tests revealed that the Mg grade decreased dramatically in the concentrate products. Pilot-scale testing of a continuous centrifugal concentrator (Knelson CVD6) on the flotation tailings revealed that a concentrate with a low mass yield, low Mg content, and high Ni upgrade ratio could be achieved. Under optimum conditions, a concentrate at 6.7% mass yield was obtained with 0.85% Ni grade at 12.9% Ni recovery and with a low Mg distribution (1.7%). Size partition curves demonstrated that the CVD also operated as a size classifier, enhancing the rejection of talc fines. Overall, the CVD was capable of rejecting Mg-bearing minerals. Moreover, an opportunity exists for the novel use of centrifugal-gravity concentration for scavenging flotation tailings and/or after comminution to minimize amount of Mg-bearing minerals reporting to flotation.