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Two-stage pressure leaching process is proposed to extract Ni from limonite-type and saprolite- type nickel laterite ore. The recommended conditions for the first stage high pressure acid leaching include acid ore ratio of 330 kg/t, temperature of 250 °C, slurry solid content of 30% and reaction time of one hour. The recommended conditions for the second stage pressure leaching include temperature of 230 °C, reaction time of one hour and slurry solid content of 35%. The nickel extraction rate of first stage high pressure acid leaching and second stage pressure leaching is 97.58% and 83.96% respectively, and the total nickel leaching rate is 93.81%, which greatly improves the utilization rate of nickel laterite ore resources. The Fe and Al concentration in solution can be reduced to below 1 g/L, which can reduce the amount of alkali used in subsequent neutralization processes. [ABSTRACT FROM AUTHOR]

Molybdenum is one of the important strategic metals, which is major produced from molybdenite with roasting process in production to yield MoO3 or ammonium molybdate. For the low molybdenum grade and high impurity contents of the non-standard molybdenum concentrate, which will cause the sintering during roasting, decrease the recovery of metals and cause pollution of environment. The main treatment methods of non-standard molybdenum concentrate were reviewed, which can be divided into two categories: concentrate purification and concentrate smelting. The extraction methods include roasting, atmospheric leaching and pressure oxidation technology etc. The pressure oxidation technology has a brilliant prospect for the advantages of high comprehensive recovery of copper, molybdenum and rehenium, strong adaptability of raw materials and no output of SO2 to pollute the environment in the process, which has a strong industrial application prospect. [ABSTRACT FROM AUTHOR]

Nitrogen-cycling processes in the deep sea remain understudied. This study investigates the distribution of nitrogen-cycling microbial communities in the deep-sea surface sediments of the western South China Sea, using metagenomic sequencing and real-time fluorescent quantitative PCR techniques to analyze their composition and abundance, and the effects of 11 environmental parameters, including NH4+-N, NO3−-N, NO2−-N, PO43−-P, total nitrogen (TN), total organic carbon (TOC), C/N ratio, pH, electrical conductivity (EC), SO42−, and Cl−. The phylum- and species-level microbial community compositions show that five sites can be grouped as a major cluster, with sites S1 and S9 forming a sub-cluster, and sites S13, S19, and S26 forming the other; whereas sites S3 and S5 constitute a separate cluster. This is also evident for nitrogen-cycling functional genes, where their abundance is influenced by distinct environmental conditions, including water depths (shallower at sites S1 and S9 against deeper at sites S13, S19, and S26) and unique geological features (sites S3 and S5), whereas the vertical distribution of nitrogen-cycling gene abundance generally shows a decreasing trend against sediment depth. Redundancy analysis (RDA) exploring the correlation between the 11 environmental parameters and microbial communities revealed that the NO2−-N, C/N ratio, and TN significantly affect microbial community composition (p < 0.05). This study assesses the survival strategies of microorganisms within deep-sea surface sediments and their role in the marine nitrogen cycle. [ABSTRACT FROM AUTHOR]

Sulfuric acid curing and leaching is a promising technology for treating refractory ores. In this work, a refractory concentrate containing 3191 ppm uranium (U), 2135 ppm niobium (Nb), and 0.7% rare earth minerals (REMs) went through two stages: curing by high-concentration H2SO4 and leaching by low-concentration H2SO4. We investigated the behavior of those valuable metals during the two stages. For both curing and leaching, the operating parameters include the acid-to-solid ratio, time, temperature, and H2SO4 concentration. The recovery for U, Nb, and REMs was as high as 95%, 86%, and 73.5% using a curing acid-to-solid ratio of 1:1, curing temperature of 200 °C, curing time of 1 h, H2SO4 concentration of 98%, leaching liquid-to-solid ratio of 4:1, leaching time of 2 h, leaching temperature of 60 °C, and leaching H2SO4 concentration of 5 g/L. A "sulfuric acid curing–leaching-U extraction by N235–Nb recovery by resin adsorption–REMs' recovery by resin adsorption" method was implemented, where the overall U, Nb, and REMs' recovery reached 93.1%, 84.5%, and 69.6%, respectively. [ABSTRACT FROM AUTHOR]

The viscosity and conductivity of the smelting slag of copper oxide concentrate are important for reducing the operating temperature. In this study, seven slag samples were prepared by the reductive smelting of copper oxide concentrate with different ferrous oxide contents. The viscosity and conductivity data of these CaO-MgO-FeO-Al2O3-SiO2 samples were measured in the temperature range of 1290~1410 °C. Based on the structural features of aluminosilicate melts, the change and dependency relationships of their viscosity and conductivity were analyzed. The results show that there is a strong tendency to form orthosilicate even when the slag composition is acidic. The formation of fayalite would allow more Al3+ to form pyroxene with the six-coordinated structure. As a result, the polymerization degree and viscosity of the melt will be reduced. The [ AlO ] 4 5 − as a network former will reduce the bonding strength of the structural units, thus reducing the slag viscosity at high temperature. In the experimental range, the logarithm of viscosity of each slag sample has a good linear relationship with its logarithm of conductivity. However, there is no uniform linear equation for these complex slags with wide composition variations. These results have potential guiding significance for the copper smelting process. [ABSTRACT FROM AUTHOR]

The leaching behavior of molybdenite was investigated in H2O2–H2SO4 solution in this paper. The results show that H2O2 was an effective oxidant for molybdenite leaching, but it had fast decomposition kinetics. A final molybdenum extraction of 73.0% was obtained under the experimental conditions of 0.5 mol/L H2SO4, 0.5 mol/L H2O2, and the fresh H2O2 addition enhanced molybdenum extraction from 73.0 to 94.5%. The leaching process was controlled by a mixture of surface reactions and diffusion, and the activation energy was 27.98 kJ/mol. Ethylene glycol enhanced molybdenum extraction and improved the stability of H2O2. Electrochemical studies suggested that the decomposition kinetics of H2O2 was faster than that of molybdenite oxidation, and ethylene glycol enhanced recovery by increasing the resistance of H2O2 decomposition and decreasing the resistance of molybdenite oxidation. XRD and XPS analysis confirmed that ethylene glycol did not alter the phase composition and the surface chemical statues of molybdenite. [ABSTRACT FROM AUTHOR]