Recovery of Valuable Metals from Nickel Smelting Slag Based on Reduction and Sulfurization Modification

Nickel smelting slag contains valuable metals including nickel and copper. Failure to recycle these metals wastes resources, and disposal of nickel slag in stockpiles results in environmental pollution. Nickel slag recycling is important, and metals can be recovered from slag by flotation. However, considering the complex forms in which valuable metals occur in nickel slag, high yields are difficult to achieve by direct flotation. In this study, nickel slag was modified by reduction and sulfurization to render it more amenable to metal recovery through flotation. The mechanism was assessed based on thermodynamics and elements’ phase distributions. Thermodynamic analyses indicated the feasibility of nickel slag modification by reduction–sulfurization smelting. The results of chemical phase analysis show that the forms in which valuable metals occur in nickel slag can be modified by reduction–sulfurization, and the proportion of metals existing in sulfide and free metal states in nickel slag can be increased. Compared with the direct flotation of raw slag, the recovery of nickel and copper from top-blowing slag increased by 23.03% and 14.63%, respectively. The recoveries of nickel and copper from settling slag increased by 49.68% and 43.65%, respectively.

Decomposition of ferronickel slag through alkali fusion in the roasting process

Ferronickel slag is a by-product of the nickel smelting process. Recycling of ferronickel slag is required since it contains valuable elements besides its potency to pollute the environment. In order to take advantage of the valuable materials and reducing the potential hazard, beneficiation of ferronickel slag is essential. Alkali fusion of ferronickel slag using Na2CO3 in the roasting process was carried out. This study aims to determine the decomposition of the mixture of ferronickel slag-Na2CO3 in the roasting process. Roasting temperature and time were 800–1,000 °C and 60‒240 minutes, respectively. Characterizations of the ferronickel slag were conducted by XRF, ICP-OES, XRD and SEM-EDS. Meanwhile, roasted products were characterized using ICP-OES, XRD and SEM-EDS. Characterization of the ferronickel slag indicates that Mg and Si are the main elements followed by Fe, Al and Cr. Moreover, olivine is detected as the main phase. The roasting process caused percent weight loss of the roasted products, which indicates decomposition occurred and affected the elements content, phases and morphology. The roasting process at about 900 °C for 60 minutes is a preferable decomposition base on the process conditions applied and the change of elements content. Aluminum (Al) and chromium (Cr) content in the roasted products upgraded significantly compared to iron (Fe) and magnesium (Mg) content. Olivine phase transforms to some phases, which were bounded with the sodium compound such as Na2MgSiO4, Na4SiO4 and Na2CrO4. The rough layer is observed on the surface of the roasted product as a result of the decomposition process. It indicates that liquid-solid mass transfer is initiated from the surface

Solubility of Palladium in Alumina-Iron Silicate Melts

Dissolution and solubility of palladium in iron silicate melts saturated with alumina–iron spinel at 1300°C has been measured using an equilibration-drop quenching technique combined with electron probe microanalysis and laser ablation–inductive coupled plasma–mass spectrometry analysis from polished sections. Composition of the resulting Fe-Pd alloy allowed estimation of the activity of palladium at different oxygen partial pressures, and, thus, the solubilities of palladium in the studied slags in conditions typical of copper and nickel smelting as well as slag cleaning at pO2=10-5 to 10-10 atm. The mechanism of palladium dissolution in the studied iron silicate slags was oxidation by formation of the monovalent oxide species PdO0.5 over the entire oxygen activity range of this study. Testing the applicability of the various palladium isotopes for quantitative analyses of Pd in these types of matrices resulted in a good fit of measured concentrations of 104Pd and 105Pd with interference-corrected 106Pd and 108Pd.

A new expansion material used for roof-contacted filling based on smelting slag

The improper handling of smelting slag will seriously pollute the environment, and the unfilled roof of the goaf of the mine will threaten the safety of the mine. Expansion materials have attracted more and more attention because of their excellent properties. In this paper, copper-nickel smelting slag that has some active ingredients of gelling is used instead of traditional aggregate and some part of cement in order to reduce its pollution to the environment and its costs. For safety reasons, hydrogen peroxide was chosen as the foaming agent. Sodium silicate and hexadecyl trimethyl ammonium bromide (CTAB) are used as additives. Our results showed that after 28 days of curing, the material has better mechanical properties and the early compressive strength of the material was enhanced by sodium silicate. The efficiency of foaming was improved by CTAB. It also proves that copper–nickel smelting slag can be used in expansion material. At the same time, the utilization rate of the copper–nickel smelting slag of this formula can reach 70%, reduce its pollution to the environment.

Energy Consumption and Greenhouse Gas Emissions of Nickel Products

The primary energy consumption and greenhouse gas emissions from nickel smelting products have been assessed through case studies using a process model based on mass and energy balance. The required primary energy for producing nickel metal, nickel oxide, ferronickel, and nickel pig iron is 174 GJ/t alloy (174 GJ/t contained Ni), 369 GJ/t alloy (485 GJ/t contained Ni), 110 GJ/t alloy (309 GJ/t contained Ni), and 60 GJ/t alloy (598 GJ/t contained Ni), respectively. Furthermore, the associated GHG emissions are 14 tCO2-eq/t alloy (14 tCO2-eq/t contained Ni), 30 t CO2-eq/t alloy (40 t CO2-eq/t contained Ni), 6 t CO2-eq/t alloy (18 t CO2-eq/t contained Ni), and 7 t CO2-eq/t alloy (69 t CO2-eq/t contained Ni). A possible carbon emission reduction can be observed by comparing ore type, ore grade, and electricity source, as well as allocation strategy. The suggested process model overcomes the limitation of a conventional life cycle assessment study which considers the process as a ‘black box’ and allows for an identification of further possibilities to implement sustainable nickel production.

Molecular Dynamics Simulation on Microstructure and Physicochemical Properties of FexO-SiO2-CaO-MgO-“NiO” Slag in Nickel Matte Smelting under Modulating CaO Content

To improve the conditions of extracting iron from nickel smelting residues, the composition modulating from FexO-SiO2-CaO-MgO-“NiO” slag source for matte smelting using high MgO nickel sulfide concentrate was carried out. Based on the molecular dynamics simulation and experimental characterization, the effect of CaO content in nickel slags on the physicochemical properties, the microstructure evolution, and the feasibility of subsequent iron extraction were analyzed. The results showed that, for nickel smelting slag with 9 wt.% MgO, 13–15 wt.% CaO and Fe/SiO2 ratio of 1.2, the melting temperature of nickel slag was lower than 1200 °C, and the viscosity was lower than 0.22 Pa·s at 1350 °C. The electric conductivity was similar to that of the industrial slag, and the interfacial tension between slag and matte was relatively large, which ensured a good separating characteristic. It not only met the requirements for the slag performances in the existing flash smelting process but also improved conditions for the subsequent iron extraction. Additionally, it could be adapted to the current situation where an increasing MgO content exists in the nickel sulfide concentrate.

AN INNOVATION OF HIGH PERFORMANCE CONCRETE BY REPLACING CEMENT WITH NICKEL SLAG POWDER

ABSTRACT Nickel slag is a solid waste produced from the nickel smelting process. At present, In Indonesia, the total capacity of domestic nickel smelting reaches 5 million tons/year with the assumption of NPI or FeNi production with a Ni level of 10%, requiring the input of Ni ore raw materials around 40 million tons/year in which around 30 million tons will become waste/slag. Currently, the area of Southeast Sulawesi has a potential of huge nickel resources of 97.4 billion tons, which spread over 480 thousand hectares of land. This has led to a continuous increase in the demand of concrete towards infrastructural development in Indonesia. Therefore, the aim of this research is to reuse nickel slag powder in the context of environmentaly friendly by analyzing the tensile strength using nickel slag powder (NSP) as a cement substitution material for the manufacture of high-performance concrete. Specimens were made with water-cement ratio of 0.31 and compared with 100% OPC Type 1 cement (as reference). Furthermore, the NSP substitution of cement were 5%, 10%, 15%, 20%, 25% and 30% with a concrete age of 3, 7, 14 and 28 days. Analysis of physical characteristics of nickel slag powder and cement were carried out by using the Le Chatelier method, while the mechanical characteristics comprised ease of work in the field (workability) and split tensile strength. The manufactured concrete was made by using Sika Viscocrete 8015 superplasticizer admixture with split tensile strength test results for NSP substitution at 28 days ≥ 5% of the value of compressive strength. Keywords: High-performance concrete, Nickel slag powder, Split tensile strength,

The Relationship between Nkx2.1 and DNA Oxidative Damage Repair in Nickel Smelting Workers: Jinchang Cohort Study

Background: Occupational nickel exposure can cause DNA oxidative damage and influence DNA repair. However, the underlying mechanism of nickel-induced high-risk of lung cancer has not been fully understood. Our study aims to evaluate whether the nickel-induced oxidative damage and DNA repair were correlated with the alterations in Smad2 phosphorylation status and Nkx2.1 expression levels, which has been considered as the lung cancer initiation gene. Methods: 140 nickel smelters and 140 age-matched administrative officers were randomly stratified by service length from Jinchang Cohort. Canonical regression, χ2 test, Spearman correlation etc. were used to evaluate the association among service length, MDA, 8-OHdG, hOGG1, PARP, pSmad2, and Nkx2.1. Results: The concentrations of MDA, PARP, pSmad2, and Nkx2.1 significantly increased. Nkx2.1 (rs = 0.312, p < 0.001) and Smad2 phosphorylation levels (rs = 0.232, p = 0.006) were positively correlated with the employment length in nickel smelters, which was not observed in the administrative officer group. Also, elevation of Nkx2.1 expression was positively correlated with service length, 8-OHdG, PARP, hOGG1 and pSmad2 levels in nickel smelters. Conclusions: Occupational nickel exposure could increase the expression of Nkx2.1 and pSmad2, which correlated with the nickel-induced oxidative damage and DNA repair change.