Electrochemical Recovery to Overcome Direct Osmosis Concentrate-Bearing Lead: Optimization of Treatment Process via RSM-CCD

The use of electrochemistry is a promising approach for the treatment of direct osmosis concentrate that contains a high concentration of organic pollutants and has high osmotic pressure, to achieve the safe discharge of effluent. This work addresses, for the first time, this major environmental challenge using perforated aluminum electrodes mounted in an electrocoagulation–flotation cell (PA-ECF). The design of the experiments, the modeling, and the optimization of the PA-ECF conditions for the treatment of DO concentrate rich in Pb were explored using a central composite design (CCD) under response surface methodology (RSM). Therefore, the CCD-RSM was employed to optimize and study the effect of the independent variables, namely electrolysis time (5.85 min to 116.15 min) and current intensity (0.09 A to 2.91 A) on Pb removal. Optimal values of the process parameters were determined as an electrolysis time of 77.65 min and a current intensity of 0.9 A. In addition to Pb removal (97.8%), energy consumption, electrode mass-consumed material, and operating cost were estimated as 0.0025 kWh/m3, 0.217 kg Al/m3, and 0.423 USD/m3, respectively. In addition, it was found that DO concentrate obtained from metallurgical wastewater can be recovered through PA-ECF (almost 94% Pb removal). This work demonstrated that the PA-ECF technique could became a viable process applicable in the treatment of DO concentrate containing Pb-rich for reuse.

A Review of Flotation Physical Froth Flow Modifiers

Over the past few decades, the need to process more minerals while lowering capital costs has led to an increase in the size of flotation cells, e.g., 0.03 m3 to 1000 m3. However, this increase has created new challenges in the operation and design of industrial flotation cells, particularly in terms of froth removal, because the distance the froth must travel increases with an increase in the flotation cell diameter. This has a negative impact on recovery. Physical froth flow modifiers can be used to improve froth removal. Their major functions are to modify and optimise the flow of the froth, improve froth drainage, reduce dead zones, and improve froth flow and removal dynamics. Therefore, physical froth flow modifiers are discussed, evaluated, and compared in this paper. The literature indicates that physical froth flow modifiers such as crowders and launders are used extensively as industrial solutions to enhance froth transport and recovery in large flotation cells. Other modifiers (including froth baffles and froth scrapers) have been found to have a profound effect on local froth phase sub-processes, including drainage and bubble coalescence. However, industrial uptake is either dwindling or limited to small-volume rectangular/U-shaped cells in the case of scrapers, or, there is no uptake at all in the case of froth baffles. Further research on how some of the physical modifiers (e.g., baffles and launders) impact the selectivity of particles is required.

Efficiency Assessment of Allflot Pneumatic Flotation Machines in Beneficiation Slime Fraction of Old Tailings at Norilsk Processing Plant

The article presents a rational technology for processing old tailings and slime (cyclone overflows) of the -25+0 microns class at tailing dump No. 1 of the Norilsk Processing Plant. One of the current and urgent problems is the lack of an efficient technology to process the slime part of old tailings with fine particles of useful metals, which is not processed and is transferred to temporary tailing dump. Current development state of the flotation equipment and technologies allows to consider the problem of coarse-size particle flotability generally solved. The results of pilot testing of the Allflot pneumatic flotation cell that operates at the 5% content of solids in the slime at Nordinves LLC are presented. Comparative materials are provided on the Allflot re-treatment slurry flotation cell (500 l) and a laboratory mechanical machine (1.5 l). The results of qualitative and quantitative calculations of the flotation process as applied to the slime fraction of old tailings are given. Conclusions about the economic feasibility of using the Allflot Pneumatic Flotation Machine for slime beneficiation are made.

A Hybrid Device for Enhancing Flotation of Fine Particles by Combining Micro-Bubbles with Conventional Bubbles

Flotation in the mining industry is a very significant separation technique. It is known that fine and ultra-fine particles are difficult to float, leading to losses of valuable minerals, mainly due to their low collision efficiency with bubbles. Flotation of fine particles can be enhanced either by increasing the apparent particle size or by decreasing the bubble size. Literature review reveals that electroflotation resulted in higher recoveries of ultrafine particles as compared with dispersed-air flotation, because electrolytic bubbles are smaller in size. To this end, the best practical approach is to combine conventional air bubbles and micro-bubbles from water electrolysis. Therefore, the design, fabrication, and operation of a bench-scale micro-bubble generator through water electrolysis is proposed. Moreover, this electrolysis unit is adapted in a mechanical Denver-type flotation cell. The resulting hybrid flotation device is capable of producing bubbles within a wide range of diameters. The significance of this process is that micro-bubbles, attached tothe surface of fine particles, facilitate the attachment of conventional-sized bubbles and subsequently increase the flotation recovery of particles. Experimental flotation results so far on the hybrid device indicate the enhancement of fine particle recovery by approximately 10% with the addition of micro-bubbles.

Feasibility of concentrating potassium minerals from Verdete ore by cell flotation

A silicate ore with K2O content above 10%, found in the central region of Minas Gerais (Brazil), called Verdete, was floated in flotation cell. The goal was to evaluate the flotation behaviour of the ore constituents (glauconite, muscovite, K-feldspar and quartz) relative to the use of different collectors (fatty acid soap obtained from rice oil, amine and oleic acid) and depressors (gelatinized cornstarch and sodium silicate). Flotation of the calcination products of Verdete with MgCl2 and CaCl2 were also evaluated. Mass recovery of flotation carried out with Verdete reached a maximum of 53% when amine and sodium silicate were used as collector and depressant, respectively. Mass recovery was directly proportional to collector dosage, and was also influenced by the type of depressor. Calcination of Verdete with MgCl2?xH2O partially consumed the micas and generated MgO. Flotation of this calcination product concentrated MgO in the floated fraction, reaching 93% when oleic acid was used as collector.

Beneficiation of Talc-Magnesite Ore with Cu-Co Mineralization

Magnesite ore with a low chalcopyrite – cobaltite mineralization was subjected to a series of separations designed to evaluate thepossible concentration of the two accessory minerals. Although the Cu-Co grade in the ore (> 0.01% Co, > 0.1% Cu) is significantlylower than the typical economic grades, content of the main valuable mineral for which the ore is mined and processed incombination with a listing of cobalt as a critical raw material, coupled with their higher price might compensate for the additionalbeneficiation stages. The ore was first crushed and subsequently classified to -100 μm and +100 -400 μm size fractions. The finefraction was upgraded by froth flotation processing in laboratory froth flotation cell. The coarser fraction was processed in severalseparation stages including gravity separation on shaking table, magnetic separation and corona electrostatic separation. The sameprocedure was also repeated with a higher-grade sample as a verification of the procedures. Preliminary results suggest that theaccessory minerals can be separated from the talc-magnesite ore and individual mineral concentrates with about 19% Co and 28%Cu were prepared. However, further work must be done to achieve desirable recoveries for the processing to be economically viable.