سید محمدرئوف حسینی

In the iron ore mines of Gol-Gohar, talc presents along with magnetite mineral, which goes to waste thickeners after recovery of magnetite. Considering that talc constitutes more than 20% of waste, it can be sold as a by-product with a high added value, if it is recovered and purified. In this study, the extraction of talc from the tailings of the Gol-Gohar complex has been investigated. Sampling was done from the central thickener underflow, which contained 65% of dust factory tailings and 35% of concentrate factory tailings. Based on characteristic studies, the tailings from the central thickener had about 23% talc. Flotation tests were performed using different chemicals, such as pine oil and polypropylene glycol as frothers, oleic acid as collector, Armac C and Armac T, and pH 7 and 11. In the best condition, pH=11, polypropylene glycol as a frother, and not using a collector, a talc concentrate with a purity of more than 95%, a weight recovery of 10.4%, and a talc recovery of 42% was produced. Also, flotation kinetic tests were performed under optimal conditions, and it was shown that most of the first-order kinetic models and the second-order kinetic model excellently match the talc flotation recovery over the time.

In recent decades, the application of microorganisms and their products for the bioseparation of minerals, bioflotation, and bioflocculation, has been extensively recognized by researchers and industry. Considering several benefits of the bioseparation, in the current paper, a detailed review has been conducted on the bioseparation of galena from its most common accompanying minerals i.e. sphalerite, chalcopyrite, and pyrite using microorganisms and their extracellular products. Based on the findings, the bacterial cells of the Thiobacillus species have a good ability to depress and selectively flocculate galena, but the cells of the Polymyxa species have a lower ability. Therefore, they depress and flocculate most of the sulfide minerals present in the pulp. In addition, the adaptation of bacteria, especially polymyxa  species with galena and other minerals will increase extracellular secretions of protein or polysaccharides. Adapted Bacillus subtilis and Bacillus megatrium can separate galena. Due to the hydrophobic nature of extracellular proteins, their less absorption on the surface of galena compared to sphalerite, causes the second mineral to be floated and the galena to be depressed. On the other hand, adaptation leads to more protein secretion in the presence of galena compared to pyrite, which will cause galena to float and the second mineral to be depressed. Also, it can be said that the tendency of extracellular polysaccharides to adsorb on galena and the tendency of extracellular proteins to adsorb on sphalerite causes that when the mixture of these two minerals comes into contact with bacterial EPS, galena is usually depressed or flocculated and sphalerite floats to some extent.

In the present study, the flocculation of fine-grained hematite was investigated in two size ranges using the bacterial cells and metabolic products of Bacillus licheniformis. More than 99% settling for fine and ultrafine particles was observed in the best condition by the bacterial cells in pH 5, and 7, respectively. Settling of fine and ultrafine particles improved by 33% and 18% compared to the control tests. Moreover, adsorption studies revealed that the settling behavior of each size, the fraction was pH-dependent and could be justified very well by the flocculant adsorption. In fact, although for fine hematite, maximum biosurfactant adhesion occurred in an acidic environment, for ultrafine hematite, neutral and basic pH caused the highest flocculant adsorption.

Isfahan province has a significant number of individual industrial soil deposits where some of them are utilized, but the silica and iron oxide impurities have deteriorate the run of mine quality and reduced the final product value extensively. The goal of this research was to eliminate the mentioned impurities to adopt the product quality with the tile and ceramic industry specifications, and for an additional added-value. Three feldspar samples were collected from Varzaneh, Naein, and Kashan regions, and chemical and mineralogical characterizations were conducted on the head samples after proper comminution and sieving analysis. The -250 µm head samples were treated by a 3 cm hydrocyclone to physically reduce the silica content, which, for all three samples and in the average, resulted in 4% silica reduction in the overflow product while alumina and unexpectedly iron oxide increased by 1.2 and 2%, respectively. Further reductions of iron oxide, 1% in average, were obtained once the overflow products were introduced to a high gradient magnetic separator. The dissolution of the amorphous silica along with iron oxides had made the magnetic products leaching, with sodium dithionite, practically ineffective. It is found that using oxalic acid as the leaching agent for the fresh run of mine feed would present the best results, as reduction of iron oxide below 1% was obtained for Kashan feldspar. Preliminary cost and benefit evaluations for a 150 t/y processing plant, determined a 50k Rl.s benefit per ton of processed product with almost 4 years of overall cost return period.

Kaolin is a clay mineral that has many industrial applications because of its special characteristics. One of the most important characteristic of this material is its whiteness and brightness. There are a lot of kaolin deposits in Iran that do not have appropriate brightness because of the presence of iron oxides in the ore. In this study, bioleaching of iron oxides by Aspergillus niger NCIM548 was applied to remove impurities from kaolin, and a model was presented to predict the extent of iron removal by this strain. Final results showed the removal of 2.2% of the total iron contents from kaolin that is promising for continuing studies in optimal conditions, and by using other strains of this fungus.