Second Pilot-Plant Bioleaching Verification of the Iron Removal from Quartz Sands

AbstractThe bioleaching processfor silicate industrial minerals using heterotrophic bacteria is a technology that has not beenapplied onindustrial scaleyet. The laboratory experimentsofiron mineral removal from quartz sands were verified during the second pilot-plant via bioleaching by usingbig bags. The composition of medium, pH, and concentration of oxygen, presence of active bacterial species, granularity and bounds of iron minerals as well as the mineralogical composition of the quartz sands were the important factors of the pilot - plant bioleaching. For industrial application, leachate permeability of big bags is very important for the release of the bacterial iron. It was observed that any inhibitory effect of the bacterial dissolution of iron during the bioleachingof quartz sands in big-bags compared with bioleaching in basins. The zeta-potential measurement of quartz sands before and after bioleaching was comparable to the surface charge of particles. Apparently, the shift reflects a loss of Fe-ions from the surface of quartz particles in leachate which leads to even more negative surface of the particles after bioleaching. In this way it was possible to remove iron from the quartz sand from 0.26% to 0.13% Fe2O3 by pilot – plant bioleaching in basins. Bioleaching resulted in a 50% decrease in Fe content of quartz sands after 83 days of bacterial treatment. The industrial washing process removed the fine fractionof Fe2O3 to 0.09%and the subsequent magnetic separation decreased Fe2O3content to 0.08%. The second pilot plant bioleaching with big bags was comparable with the first pilot plant tests and also with laboratory tests of the iron removal. This bioleaching pretreatment may be used for the removal of fine undesirable iron minerals from the surface of industrial mineralsunder the stationary solution conditions

Participation of bacteria in weathering processes of silicates

Biological processes presented by the metabolic activity of different species of bacteria adhered at the mineral surfaces are a part of the geochemical processes. These bacteria accelerate, by the production of organic acids into the minerals structural bonds, the leaching of elements and their subsequent and gradual transformation to the secondary minerals. Microbial destructions of silicates are studied in order to processing low-quality mineral raw-materials and the remediation of soils, sediments and waters contaminated by industrial pollutants. The samples of material, used in our research, were obtained at 9 deposits of non-metallic raw-materials in Slovakia. The sediment sample was taken from the area of Baikal Lake. The presence of microorganisms in the matrix most frequently was determined by a subsequent isolation of microorganisms and identification of bacterial species presented in the silicate matrix. The species of Bacillus and Pseudomonas genus were the common representative of the microorganisms

Preparation of iron oxides and oxihydroxides

Iron oxides are common minerals that occur in the environment, either naturally or as a result of human activities.The most common Fe(III)-hydroxides and -oxides include ferrihydrite (Fe5HO8 .4H2O) that transforms to hematite (a-Fe2O3 ) and/or goethite (a-FeOOH).That depends on the solution composition, temperature and pH. Depending on the composition of the solid and solution, oxidation can transform the green rust (a product formed by a metal corrosion) to lepidocrocite (γ -FeOOH) or magnetite (Fe(II)Fe(III) 2O4 ). Weathering can degrade magnetite to maghemite (γ –Fe2O3 ) and all of the Fe-oxides are subject to an attack and dissolution by organic acids and ligands that are formed during the breakdown of biological material. Iron oxides can be prepared by hydrolysis of acidic Fe3+ solutions or by controlled oxidation of Fe2+ solutions. Goethite, lepidocrocite and magnetite were prepared by oxidation of Fe2+ solutions under slightly different values of pH, Fe concentrations and rates of oxidation. Maghemite was prepared by a thermal transformation from synthetic lepidocrocite heated in a furnace at 250 °C for 2h. Hematite was prepared by forced hydrolysis of Fe3+ solution from a chlorine system (FeCl3) at the temperature close to 100 °C under strongly acidic conditions (pH 1-2). Main mineral phases were confirmed by the RTG diffraction and IR spectroscopy method. Iron oxides are excellent, renewable adsorbents, and often control free metals through adsorption reaction

A combination of bioleaching and electromagnetic separation in the treatment of quartz sands

This contribution deals with the treatment of Slovakian eolic quartz sands by bioleaching and magnetic separation with the aim to remove iron. The X-ray study of sand patterns confirms that quartz occurs as a dominant mineral. Accompanying minerals are represented by smectite and feldspars. As to the sample of unground sand, bacterial leaching resulted in a Fe2O3 reduction to the content of 0.13 %. Similarly, in case of ground sample, the Fe2O3 content was decreased to the value of 0.19 %. Thus, biological leaching removed 60 % of Fe and by following leaching by oxalic acid total the iron removal was 70.5 %. Finally, the application of magnetic separation resulted in the total iron removal of 93 % and, in such combined way, the prepared product contained 0.024 % of Fe2O3. Achieved results on the iron removal points to the fact that the combination of leaching and magnetic separation enables to obtain a product usable in glass industry

Study of Cu(II) Adsorption by Siderite and Kaolin

AbstractThis work deals with the study of adsorption properties of natural raw materials – siderite (S) and kaolin (K) as potential adsorbents of heavy metals cations. To enhance their adsorption capacity, the coating of their surfaces by MnO2 was used (samples denoted as SM and KM). The changes of the surface parameters after the modification were studied by the low temperature nitrogen adsorption measurement. More expressive increase of the value of SBET was observed for the sample SM, from 6 to 36 m2 g-1. The nonhomogenous distribution of MnO2 particles of needle shape on the siderite surface was observed by SEM.The results from the batch adsorption experiments of Cu(II) removal were processed by the Langmuir adsorption isotherm. The calculated value of maximum adsorption capacity increased after the modification from 12.9 to 19.8mg g-1 and from 10.8 to 39.8mg g-1 for siderite and kaolin, respectively. In the introductory experiments in dynamic regime, the columns filled with mixtures of S-K and S-KM were percolated with Cu(II) model solution. Due to the presence of a higher dose of S, the solution pH increased during the percolation and precipitated copper was retained in the columns. During the first hours, the effectivity of both mixtures reached 100% and then slightly decreased to 85% in average

Dissolution of Iron During Biochemical Leaching of Natural Zeolite

Natural zeolite, including clinoptilolite, often contains iron and manganese which decrease the whiteness of this sharp angular material.The biological treatment of zeolite enables its use as an substitute for tripolyphosphates in wash powders which have to comply with strict requirements as far as whiteness is concerned and rounded off grain content. Insoluble Fe3+ and Mn4+ in the zeolite could be reduced to soluble Fe2+ and Mn2+ by silicate bacteria of Bacillus spp. These metals were efficiently removed from zeolite as documented by Fe2O3 decrease (from 1.37% to 1.08%) and MnO decrease (from 0.022% to 0.005%) after bioleaching. The whiteness of zeolite was increased by 8%. The leaching effect, observed by scanning electron microscopy, caused also a chamfer of the edges of sharp angular grains. Despite the enrichment by fine-grained fraction, the decrease of the surface area of clinoptilolite grains from the value 24.94 m2/g to value 22.53 m2/g was observed. This fact confirms the activity of bacteria of Bacillus genus in the edge corrosion of mineral grains.Removal of iron and manganese as well as of sharp edges together with the whiteness increase would provide a product suitable for industrial applications

Bioleaching of Zn, Ni and Fe from contaminated sediments of water reservoir Ružín I with using heterotrophic bacterial strains

This study investigates the bioleaching of the zinc polluted sediment from water reservoir Ružín I using heterotrophic bacterialstrains ubiquitous in sediment environment. The effect of bacterial activity, pH, iron solubilization and precipitation and bioleachingmedium were evaluated. The pH value controls the bacterial activity during the leaching process. Addition of glucose to the bioleachingmedium accelerated the bioleaching rate. The results indicates, that the leachibility of zinc depend on the geochemical formsand surface interaction between metal and sediment fraction. Sequential chemical extraction confirm, that Zn was predominantly boundto the iron-manganese oxides

Significance of bioleaching method in dissolution of iron and in the quality improvement of non-metallics

Simple laboratory bioleaching experiments for the iron removal with heterotrophic bacteria on natural raw materials were conducted to explore a simple cyclic operation for a potential use at the industrial scale. Heterotrophic bacteria of Bacillus spp. growing in the presence of feldspar raw materials are able to dissolve iron. Anaerobic conditions Quickly formed by bacteria enable a simple manipulation with the sample solution. Insoluble Fe(III) in the feldspars sample could be enzymatically dissolved as Fe3+ and also reduced to soluble Fe2+ by silicate bacteria of Bacillus spp. This metal was efficiently removed from the feldspars sample as documented by a Fe2O3 decrease (from 0.29 % to 0.12 %) after bioleaching in the conical flask and by a Fe2O3 decrease (from 0.29 % to 0.19 %) after bioleaching in the percolate column. Bioleaching of Fe was more effective in the conical flask. Iron-bearing minerals can be easily removed by magnetic separation, but ultra fine iron particles are difficult to treat by conventional mineral processing methods. Thus bioleaching is an attractive alternative for effective removal of iron minerals. The removal of iron with the whiteness increase should give a product, which is fit for industrial ceramic applications

Bioleaching Process for Copper Extraction from Waste in Alkaline and Acid Medium

Flotation wastes are becoming a valuable secondary raw material and source of many metals and semimetals worldwide with the possibilities of industrial recycling. The flotation tailings contain oxide and sulfide minerals that have not been sufficiently stabilized and form acidic mine waters, which in turn contaminate groundwater, rivers, and reservoi6sediments. An effective way to recycle these mine wastes is to recover the metals through leaching. While the focus is on acid bioleaching by iron- and sulfur-oxidizing bacteria, alkaline leaching, and the removal of iron-containing surface coatings on sulfide minerals contribute significantly to the overall environmental efficiency of leaching. For this study, static and percolate bioleaching of copper from flotation waste at the Bor copper mine in Serbia was investigated in alkaline and then acidic environments. The aim of the study was to verify the effect of alkaline pH and nutrient stimulation on the bioleaching process and element extraction. A sample was taken from a mine waste site, which was characterized by XRF analyses. The concentration of leached copper was increased when copper oxide minerals dissolved during alkaline bioleaching. The highest copper yield during alkaline bioleaching was achieved after 9 days and reached 67%. The addition of nutrients in acidic medium enhanced the degradation of sulfide minerals and increased Cu recovery to 74%, while Fe and Ag recoveries were not significantly affected. Combined bioleaching with alkaline media and iron- and sulfur-oxidizing bacteria in acidic media should be a good reference for ecological Cu recovery from copper oxide and sulfide wastes