INTL. SYMP. ON SUSTAINABLE MINERAL PROCESSING: PRINCIPLES, TECHNOLOGIES AND INDUSTRIAL PRACTICE

This work contains the results from experimental testing on the process of oxidation copper leaching under pressure from concentrate obtained after the re-flotation process of tailings. Flotation tailings are a significant resource for recovery of copper and other useful components, since their content in tailings is approximate to the content in the primary raw materials. On the other hand, the dumped flotation tailings, under the influence of the atmosphere, pollute the surrounding land, surface waterways, as well as the groundwater, and present a serious environmental problem.
Larger global companies are involved in research related to the process of obtaining the useful components from tailings. Testing the flotation process at the site Katanga [1] was focused on valorization of copper and cobalt from tailings. In the Musselwhite Mine in Ontario, the process of flotation concentration [2,3] has confirmed that this is an effective method for reducing the content of sulphides present in tailings. The effect of sulfuric acid concentration as a leaching reagent was tested, as well as the effect of temperature, pressure, and pulp density on the degree of copper leaching. The obtained results indicate that the use of combined procedure of re-flotation tailings and copper leaching under pressure achieve a high degree of copper separation of over 98%.

The major environmental impacts from tailing disposal can be divided into two categories: (1) The loss of productive land following its conversion to tailing dump, and (2) the introduction of sediment, acidity, and other contaminants into the ecosystem. The tailing system continues to generate opposition from local communities, the general public, and non-government organizations (NGO). The project was completed as follows: (1) Identification, characterization and settling study; (2) Preparation of synthetic tailing mixtures; (3) Characterization and settling studies; (4) Pressure filtration and paste thickening studies; (5) Study of flow properties of filtered tailings and rheology of thickened (paste) tailings; (6) Assess the transportability of filtered and paste tailings; (7) To evaluate the flow properties and paste rheology (8) Address issues related to the storage and transportation. The project concluded that tailing samples are amenable for paste thickening as well as filtration. It is possible to get a paste with 56-72% solids and yield stress in the range of 75-300 Pa. The tests revealed that it is possible to produce a filter cake with moisture content ranging from 14 to 24%.

India's 2030 vision requires a huge amount of quality iron ore, and the utilization of low-grade iron ores such as banded iron ores will play an important role to achieve the same. The absence of alumina impurities in the Banded Hematite Jasper (BHJ) ore provides it an edge over other low-grade iron ores, and has a promising potential as feed material in a blast furnace. The conventional beneficiation techniques such as magnetic separation, spiral concentration, and washing are ineffective in producing suitable feed (Fe~60%) for the blast furnace. It is found that microwave exposure provides significant enrichment to the low-grade iron ore and can be used as a pretreatment step in the beneficiation of similar low-grade iron ores. The above study reveals that hematite and magnetite are strongly susceptible to microwave exposure, which enhances separation of iron values from impurities. The pretreatment process for beneficiation includes only microwave exposure, and no chemical additive and may prove economical and industrially feasible. Under optimal conditions, an iron-enriched concentrate with 61%Fe, 85% Fe recovery at 50% yield can be achieved from feed ~37 % Fe, whereas the carbothermal reduction in the microwave reactor yields ~68% Fe at 95% iron recovery under optimal conditions.

Atomic absorption spectrophotometer technique was employed to measure the contents of the heavy metals in the effluents directly released from tannery industries. These effluent samples were first subjected through wet acid digestion process for decomposition of organic substances and concentration of the metals being measured in the samples. The measured concentration of the heavy transition metals by AAS technique was analyzed and it was concluded that this spectrophotometer method can analyze a remarkable concentration of the effluents metals. Therefore, the quantitative measurement of most of the metals in tannery waste is preferable by AAS method. These results overall give a picture that the environments are greatly being contaminated due to high Cr, Fe, Pb concentrations as well as other toxic chemicals found in the discharged effluents from tanneries

The efficiency of enriching diamond-bearing ores can be improved by developing and introducing new energy-saving methods aimed at increasing the quality of concentrates via kimberlite softening, the selective identification and withdrawal of diamond crystals in milling ores, and finding new distinctions and enhancing the contrast between the physicochemical, electrophysical, and luminescent properties of diamonds and other rock-forming minerals [1, 2].
In this work, we present the results from a comprehensive study of the mechanism behind the action of a high-power (high-voltage) nanosecond electromagnetic pulse (HPEMP [3]) on the structural chemical and physicochemical properties (electrostatic potential and hydrophobicity) of the surfaces of synthetic and natural technical diamonds. Our aim was to assess the efficiency of using HPEMP in the enrichment of diamond- bearing ores.
We used samples of AS-120 synthetic diamonds with particle sizes of (-50 +40) mkm, along with crystals of natural technical diamonds (-2 +1) mm in size from the Triassic placer of the Bulkur site in the Nizhne Lenski region of Russia.
The mineral samples were treated with high-voltage nanosecond videopulses (pulse front ~1.5 ns, pulse duration ~50 ns, and pulse amplitude U~25 kV; the field strength (E) is equal to ~10(to the power of 7) V/m; pulse repetition rate=100 Hz; pulse energy ~0.1 J; range of the change in treatment time t(treat)=10-150 s; number of pulses N(pulses)~(1-15)x10(3)).
Fourier transform infrared spectroscopy (FTIR), analytical electron and atomic force microscopy, and physicochemical examination of the structure and properties of mineral surfaces are used to study changes in the structural defects, functional and chemical compositions, and surface electrical properties and hydrophobicity of diamond surfaces exposed to nonthermal nanosecond high-voltage pulse treatment. Hammett indicator adsorption in aqueous media [4] was used in our analysis of acid-base centers (functional chemical composition) on the surfaces of synthetic diamonds. A Shimadzu UV-1700 spectrophotometer was used to measure optical density in standard water solutions of acid-base indicators at wavelengths corresponding to their optical absorption maxima.
According to the data obtained via spectrophotometric analysis and XPS, the nonthermal action of nanosecond high-voltage pulses ( t(treat)~10-30 s) on synthetic diamonds produced targeted structural chemical transformations of diamond crystal surfaces, i.e., the hydroxylation and/or hydration of the minerals surface.
Considerable changes in the natural diamond IR spectra were observed after the electric pulse treatment of crystals with iron oxide mineral films, strongly adhesive clayish mineral coatings, and other impurities on their surfaces. Samples with phase impurities containing hydrocarbon and OH groups lost them after HPEMP treatment. For example, the IR spectrum of one crystal showed a sharp drop in the intensity of the spectral lines at 2918, 2849, and around 3400 cm-1 after t(treat)>50 s. This usually indicates the presence of hydrocarbon impurities and H2O.
Due to the cracking peeling, destruction, and removal of hydrophilic mineral films from the surfaces of diamond crystals, the relative share of hydrophilic diamonds fell by 22% (from 45 to 23%) and reached its minimum at t(treat)~150 s, while the number of crystals with mixed properties grew. Improvement in the hydrophobic properties of diamond samples as a result of HPEMP treatment was observed at t(treat)~50 s, while the increased duration of treatment was accompanied by a reduction in the number of hydrophobic crystals.
Analysis of our IRFS results showed that the nonthermal action of nanosecond HPEMP resulted in a notable systematic increase in the absorption coefficient of the line around 1365 cm-1, indicating there was an increase in the concentration of lamellar B2 defects (platelets) represented by internode carbon atoms. The action of nanosecond HPEMP can presumably generate new B2 centers inside diamonds of the medium-nitrogen crystal group, mostly in those with layered octahedron internal structures and elevated shares of nitrogen B defects. The effect of consistent increases in the concentration of B2 defects in our investigated natural diamond crystals upon lengthening the duration of electromagnetic pulse action was registered for the first time. According to IR spectroscopy, nanosecond HPEMP treatment of diamonds helps cleanse diamond surfaces of phase impurities, improves diamond transparency and hydrophobicity, and apparently enhances the strength of crystals due to increased concentrations of B2 defects.
Lengthening the period of irradiation (the dose) to 150 s resulted in oxidation of the diamond surfaces by products of water-air medium radiolytic decomposition, which led to the production of hydroxyl and/or carbonyl groups on the crystal surfaces, a further shift of the diamond electrokinetic and electrostatic potential into the region of negative values, and deterioration of the diamond's hydrophobic properties.

The Northeast of Brazil, essentially in the Borborema Province [1], have small-scale mining as a secular activity, promoting livelihood and economic development of cities with mining vocation [2][3]. Junco do Seridó is a town located in the Brazilian State of Paraiba, with privileged rich geology in pegmatite fesdspatic bodies with low iron levels, fastened in quartzites of the Equador Formation. The chemical weathering in acidic conditions [4] in the region promoted degradation of pegmatites, turning feldspars and other silicates in kaolinite with impurities of quartz, muscovite, iron oxides-hydroxides, tantalite and several clay minerals. The kaolin is drawn by hand, initially in open pit front. With the advancement of depth, the mining evolves underground, always handmade, rustic, dangerous, and unhealthy. The goal of this study is to show how the artisanal mining of kaolin influences livelihoods and promotes the economic development of the municipality, but on the other hand causes environmental impact and serious damage to the health of miners. The precariousness of working conditions associated with the lack of surveillance, mining planning of technological innovation, and the absence of recovery projects of degraded areas, altogether cause a mismatch between economic development, social welfare, occupational health, and environmental balance in small-scale mining.

The industrial processing industry is under continuous sustainability pressure from environmental, legal, and financial quarters to use less water, and industrial processing plant designers and operators are obliged to consider the option of operating at higher concentration [1]. As the concentration of fine particle industrial processing suspensions increases, viscous stresses also increase, and inevitably become non-Newtonian in nature. For some years, our industrial flow process research group has been researching the behaviour of high concentration non-Newtonian suspensions in pipes, valves and fittings, pumps and launders, and these will form the focus of the paper. The aim of this paper is to highlight the important practical aspects of these fundamental issues [2], and their implications for design for industrial process suspension handling. In particular, the objective is to present the principal conceptual issues that underpin sound design for industrial process suspensions. The introductory detail of the design process for handling industrial suspensions will be presented in this paper. The important point to make at the outset is that the foundation of sound design for industrial suspension handling does not revolve around the task of choosing or producing special materials and plant - although these are often required. The foundation lies rather in having a good understanding of the industrial suspension fundamental viscous properties, and sustainable industrial process design and operation [3], which is the basis of this paper and our work at the industrial flow process research group.