Calcination of low-grade laterite for concentration of Ni by magnetic separation

With the continuous depletion of high-grade nickel ores such as millerite and niccolite, nickeliferous laterites have become the major source for the production of nickel metal. However, only 42% of the world’s production of nickel comes from laterites, since the concentration of Ni is relatively low (ca. 2 wt.%). In addition, other metals, such as magnesium, iron and silicon can be found in laterite, which make the concentration of nickel even more difficult.In this study, a low-grade nickeliferous laterite ore was first calcinated and then processed by using a wet magnetic separator in order to recover nickel. Since, the ore contains both Ni and Fe, the calcination of laterite is effective in altering the crystalline structure of Fe species and therefore its magnetic properties, which in turn enable the selective concentration of nickel by magnetic separation that is an easy and environmentally-friendly technique. The experimental results have indicated the importance of carefully controlling: (1) the calcination temperature; (2) the pulp density and (3) applied magnetic field strength. The main finding of this work was that magnetic separation is effective in recovering 48% of nickel from laterite, increasing the Ni grade in the recovered product from 1.5% to 2.9%, when prior to the separation the ore was calcinated at 500 °C for 1 h.     

Sorting Techniques for Plastics Recycling

This paper presents the basic principles of three different types of separating methods and a general guideline for choosing the most effective method for sorting plastic mixtures. It also presents the results of the tests carried out for separation of PVC, ABS and PET from different kinds of plastic mixtures in order to improve the grade of the raw input used in mechanical or feedstock recycling.     

Measurements of size distribution of titanium dioxide fine particles in a highly concentrated non-aqueous suspension by using particle self-assembly under an electric field

This paper describes the measurement of size distribution of TiO₂ fine particles in a highly concentrated non-aqueous suspension by using self-assembly of particles under an electric field. Interactive force apparatus (IFA) was used to conduct the measurement. IFA first assembled pearl chains of particles between two electrodes, and then applied the compressive force to change the pearl chain structure by shortening the distance between electrodes. The repulsive force generated when the chain curved while the attractive force created when the chain was broken. The cycle of repulsive and attractive forces corresponds to the size of particles. The results obtained with IFA were compared with results obtained from size measurement by analyzing SEM photographs. IFA indicated the comparable results with the one obtained using SEM. The particle size distribution measured by IFA decreased as a result of increasing the supply voltages. Changes in correlation between size distribution measured by SEM and IFA at different supply voltages were observed in different size ranges. At smaller than 300 nm, result at 0.24 V fit well with the SEM result while at >600 nm gives better agreement with the results at 0.48 V. The difference is mainly due to the increase in number of particles in fine size fraction with increasing supply voltages. Decrease in size indicated that the breakage of aggregate particles and/or disintegration of doublet particles occurred due to the electrical fragmentation. The fragmentation was explained by monitoring the mean diameters and their deviation obtained from IFA measurements at different supply voltages.     

Removal of Anionic Metal Ions from Wastewater by Hydroxide-type Adsorbents

Generally speaking, anionic metal concentrations in wastewater from industries and mineral processing plants are well above the allowed limits for effluent set by the Ministry of Environment of Japan. Nowadays, the removal of anionic ions has been considered difficult and development of new process is desperately needed. In this paper, we report the development of three hydroxide-type adsorbents, illustrating their adsorption efficiency in removing As, Se, Mo and Sb ions from aqueous solutions. The main finding of this work was that the adsorption behavior was influenced very much by both the pH and the adsorbent concentration. Nevertheless, the newly developed hydroxide-type adsorbents were very effective in reducing the concentration of those anionic ions.     

Measurement of particle size distribution of silica nanoparticles by interactive force apparatus under an electric field

This paper describes the measurement of particle size distribution of silica nanoparticles by interactive force apparatus (IFA) under an electric field in order to suggest the application of the apparatus to the measurement of particle size distribution. The results were compared with results obtained from size measurement by dynamic light scattering. D₅₀ measured by IFA was closer to the average particle size determined by TEM (5 nm). Also, when compared the results under three different supply voltage, (1) the results at 0.01 and 0.02 V were almost identical while (2) these results were different from the one at 0.04 V. The results indicate that breakage of coagulated particles possibly occur due to electric breakdown. The distribution measured by IFA (D₅₀ = 5–7 nm) was larger than the one measured by DLS (D₅₀ = 1 nm). The electric breakdown was explained by curve fitting of three different particle size distribution functions with particle size distribution obtained from IFA measurement.