Milan Trumic

A Kinetic Study of Micronization Grinding of Dry Mica in a Planetary Ball Mill

This paper presents results of the research of micronization grinding of dry mica in a planetary ball mill. Investigation was conducted in order to improve the quality and to obtain clearly defined properties and characteristics of mica powder. The micronization grinding of dry mica was performed in four time periods: 30, 60, 120, and 360 minutes. The micronized powder was investigated by means of differential thermal and thermogravimetric analyses, analysis of the degree of micronization, the specific surface area analysis, and X-ray diffraction analysis. The achieved results pointed out that dry mica micronization grinding which exceeds 360 minutes is recommended for this type of mill. However, it was also shown that the micronized mica produced by means of planetary ball mill after extra long periods of micronization grinding can pass into amorphous state.

Results of fibre and toner flotation depending on oleic acid dosage

The literature was reviewed with respect to deinking flotation methods with toner samples, specifically emphasizing the speciation of copy machine and laser printing, which produce an increasing quantity of paper that is difficult to recycle. Speciation here refers to the physical-chemical characteristics of the toner, which change because of the polymerization (fusion) and oxidation process, due to exposure to heat, light and oxygen (air) during the printing process. To simulate the deinking flotation, after the ideal disintegration process, samples of toner were prepared in order to provide free toner particles. Synthetic toner has iron content and the same physical-chemical features as free disintegrated printed toner particles. We report the toner (I) and fibre (Y) recovery and the brightness (B) of laboratory filter pads formed of deinked product as deinking efficiencies. The application of oleic acid as the collector in the flotation stage gives a better flotation recovery in alkaline than in acidic conditions. The highest brightness (BF = 93.66%) and flotation recoveries (I = 90, Y = 92.82%) were achieved during testing at an oleic acid concentration of 3.38·10−6 mol l−1, which is the lowest dose used. This makes the use of oleic acid economical and environmentally friendly.

The application of mineral processing techniques for the printed paper recycling

This paper describes the waste paper recycling process. Special emphasis is placed on the description of technological phase (disintegration or grinding, screening, cleaning, washing and/or flotation, water treatment and disposal of sludge), which are generally required in the processing of waste paper, and which also represent the main phases in the mineral processing. The waste paper is a potential secondary raw materials but due to degradation of cellulose physical properties which occur during the recycling, the cellulose fibers can be recycled a limited number of times. Because of this, the impact analysis of mechanical and chemical treatment on the secondary fiber quality is also given in the paper.

Leaching of low-grade copper ores: A case study for 'Kraku Bugaresku-Cementacija' deposits (Eastern Serbia)

This paper deals with the investigation of column leaching of low-grade ores from the copper mine Cerovo, Serbia (the approximate Cu content in the ore ranges from 0.2 - 0.3 % with >10 % copper in the form of oxide minerals). The leaching experiments were performed using sulphuric acid solutions, whereby the kinetics of copper leaching was investigated with respect to acid concentration and solid to liquid ratio. The copper concentration in the leach solution ranged from 0.80 to 1.75 g dm-3. The total Cu recovery rate ranged from 30 to 56 %, whereas the recovery rate of copper oxide minerals ranged from 67 to 100 %. Furthermore, with increasing the amount of liquid phase, copper recovery increases as well, and copper oxide minerals were completely leached out. Besides copper ions, considerably high ferrous/ferric ion concentrations were achieved in the leach solution. This concentration was sufficiently high for the use of either solvent extraction or ion exchange techniques or both for further treatment of the leach solution.

Effect of Operating Parameters on the Mechanical Activation Process of Mica Powder

Mechanical activation of mica is a great technological and technical problem because of their specific crystallochemical structure. This is dependent upon the type of equipment used and the type of disintegration process. The paper presents the investigations of kinetics of operational parameters, effect on properties and structure of powder mica, etc. The mica sample was subjected to mechanical activation in ultra-centrifugal mechanoactivator with a peripheral comminution path. During the investigation, some operating parameters, viz. number of rotor revolutions (rpm), sieve mesh size (µm) and current intensity (A), and some technological parameters, viz. time of mechanical activation, t (min), circumferential rotor speed, v (m.s−1), capacity of ultra-centrifugal mechanoactivator, Q (kg.h−1) and specific energy consumption, W e (kWh.t−1) were monitored. Analyzing the results it can be concluded that the rate of mechanical activation of mica was increased with the increasing load and rotor revolution of ultra-centrifugal mechanoactivator with peripheral comminution path. Under these conditions, the powder mica was transformed into amorphous state. It was confirmed by X-ray and thermal analyses.