External flows are process streams that come from auxiliary processes or events. They are re-routed into the ordinary flowsheet since they are thought to be too valuable to be sent to any tailings pond. External flows come from multiple sources, e.g. drainage sumps, spillage thickeners, depleted products etc. Therefore, external flows may fit or not fit into an existing flowsheet depending on several factors like, flow rate frequency, dilution ratio variation, chemical and mineralogical composition, particle size or particle morphology. By using Particle Texture Analysis to investigate external flows and compare them with existing ordinary flows it is possible to pinpoint from a process mineralogy via point to what extent the external flow fits into the ordinary processing flowsheet. Results from this information category helps to reach a higher quality of process knowledge and control for every step in the concentrator. Results show that some recycled flows reconnected to the main flow are not connected to the best point. A side effectof the analysis is that some flows may be sent to later grinding stages. Thus, decreasing the load on the primary mill, and increasing the retention time.
Adsorption, contact angle and flotation of anionic Atrac and non-ionic ethaloxylated nonylphenol surfactant, and their mixture on apatite and magnetite were studied. The effect of calcium ions and sodium silicate on Atrac adsorption was investigated. The effect of Atrac adsorption on the contact angle data of apatite and magnetite in the presence and absence of sodium silicate was also examined. Wettability of solids depends on solids surface free energy and the surface energies of apatite and magnetite powders were calculated from polar and non-polar liquid contact angle data. A decrease in particle size increased the polar contribution to surface free energy due to unsaturated broken bonds on the surface. Atrac is seen to adsorb equally on apatite and magnetite, and the adsorption increased in the presence of calcium ions. The presence of water glass decreased the Atrac contact angle data on magnetite and also the flotation response demonstrating its role as magnetite depressant in flotation. The presence of non-ionic surfactant enhanced the Atrac flotation of apatite with no flotation of magnetite. Bench-scale flotation tests showed that 50% of Atrac can be replaced with non-ionic collector without impairing the flotation results. Results also illustrate that the non-ionic adsorbs on apatite in equal amount of Atrac collector signifying 1:1 composition of anionic and non-ionic collector on apatite surface. Nonionic head group sitting in between anionic head groups screens the electrostatic repulsion and forms compact adsorbed layer on apatite surface thereby increasing the hydrophobicity and flotation.
Scientists and technologists in world over are making large efforts to streamline the conventional technological schemes of ore processing, in particular froth flotation towards reducing overall costs, limiting the use of dangerous substances, decreasing waste streams and improving waste disposal. Hitherto, search for such innovations has been performed mainly empirically and there is an urgent need to shift these technologies to be more innovative and effective. Understanding of the fundamental concepts of aquatic chemistry of minerals-selective adsorption and selective redox reactions at mineral-solution interfaces would impact innovating conventional flotation process Molecular-level knowledge and coherent understanding of minerals contacted with aqueous solutions is required which underlie great opportunities in controlling mineral-solution interfaces towards the grand challenge of tomorrow's science and mineral processing technology. Aqueous redox chemistry of sulphides and adsorption mechanisms, the problems of metal sulphides selectivity against pyrite and fine particle flotation have been highlighted and discussed in the light of literature. The requisite knowledge and research needs to address these issues have also been briefly presented.
Low grade iron ores with impurity gangue minerals containing silica and alumina must be upgraded to an acceptable level of iron content. Concentrates, due to their fine sizes, are not suitable to be directly charged to the iron-making processes such as the blast furnace or the DR-plant. Hence, an agglomeration technique should be applied to fine concentrate. The most commonly employed one is pelletizing in iron ore industry. In pelletizing, iron ore, water and a binder are balled in a mechanical disc or drum to produce agglomerates. Bentonite is the most widely used binder. However, it is considered as an impurity due to its high SiO sub(2 and Al2O3 content. Many researchers have investigated different binders, mostly of organic origin, in pursuit of finding a viable alternative binder to bentonite. Organic binders were found to yield good quality green and dry pellets. However, they fail to impart enough strength to the pre-heated and fired pellets as a result of insufficient slag bonding. Boron compounds free of silica and alumina are thought to be a potential solution to overcome the lack of slag forming constituents encountered with organic binders as they are known for their low melting temperatures as well as for their ability to also lower the melting temperatures of silicates. A few researchers have investigated the use of boron compounds in iron ore agglomeration and found promising results which have been covered in this paper.)
Studies on boron, its mechanism and health effects are growing although the safe limits of daily boron exposure have not been clarified. Current knowledge about the toxic levels of boron on humans is not sufficient and needs to be improved. The main toxic effect of boron in animals involves the reproductive system, including specific adverse effects in the male reproductive tract in rats, mice and dogs. Boron determination in biological matrices needs sufficiently sensitive procedures for detection at trace levels, and many techniques do exist. In this paper, we reviewed the general view of potential impact of boron on health, exposure of boron and its determination techniques.
For over twenty years boron has been of interest to investigators confirming the safety and essentiality of the element in humans. Fruits, vegetables, nuts, and pulses are natural sources of boron in the diet which world wide averages about 1-3 mg daily for most adults. In boron-rich regions of Turkey drinking water sources with 29 mg boron/liter are consumed without harmful effects. The European Union established a safe drinking water standard of 1.0 mg boron/litre a level difficult for some regions to achieve. Safe standards are difficult to establish due to limited information and widely varying boron concentrations in food and water, high exposures in boron-rich regions or occupational settings and voluntary intakes, for example, of boron containing products. Current research implicates boron as an essential nutrient in humans demonstrating healthful effects in cellular functions associated with osteoporosis, arthritis, inflammation and cancer. Proposed mechanisms of action implicate that boron, found in cells as boric acid, participates in important membrane functions and intracellular signaling cascades. Traditionally, biochemical mechanisms associated with healthfully beneficial effects are needed for nutrients to meet the criteria for essentiality in humans. While boron meets the traditional criteria to be determined essential in humans the research process has provided additional insight into essentiality for boron insight that essentiality for trace elements may based on different criteria. The study of boron in living systems provides a more fundamentally important role by demonstrating functions for trace elements differing from those needed to confirm essentiality previously for carbon based compounds, i.e., carbohydrates, lipids, proteins, and vitamins in human nutrition. To conclude, boron can be a model element to introduce a new field of study, 'elementomics'. Further studies from boron-rich areas are needed to determine essentiality, dietary requirements, metabolic functions, therapeutic applications, economic benefits and important public policies for boron, a biologically important trace element.
Flotation of soluble salt minerals such as potash, trona and borax exhibits similarities because all are conducted in their brine solutions. The most commercially important boron minerals in the world are borax (Na sub(2B) sub(4)O sub(7.10H) sub(2)O), colemanite (Ca sub(2B) sub(6)O sub(11.5H) sub(2)O), ulexite (NaCaB5O sub(9.8H) sub(2)O), and kernite (Na sub(2B) sub(4)O sub(7.4H) sub(2)O). Most of them contain low grades when mined and must be upgraded by mineral processing techniques to commercially acceptable quality for the production of basic chemicals, such as boric acid. Boron minerals exhibit a spectrum of solubilities depending upon the cations in the lattice structure. Accordingly, a classification of semi-soluble (colemanite and ulexite) and soluble (borax and kernite) boron minerals may be appropriate as each class of minerals behaves differently in flotation. While borax has to be concentrated from its saturated brine, colemanite and ulexite can be recovered by flotation as is the case for other semi-soluble salt minerals. A common problem encountered in both classes of boron minerals is the presence of significant amounts of clay type minerals which adversely affect flotation recoveries in the form of slime coating. Despite the successful application of flotation technology in the potash industry, flotation has not yet been well developed for boron recovery. This may be attributed to inherent difficulties such as high ionic strengths, high viscosity brines, interaction of cations at the solid/liquid interface, and particularly the presence of clay minerals acting as persistent slimes. In this paper, we have reviewed the flotation chemistry studies on the interaction of boron minerals with anionic (sodium dodecylsulfate) and cationic (dodecylamine hydrochloride) surfactants along with the electrokinetics properties of boron minerals.