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1

Influences of magnesium ions in water on gelatinization characteristics of starch and its flocculation behaviors on particles

Tang Min, Niu Xiaoying, Wen Shuming

Physicochemical Problems of Mineral Processing

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2024

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Vol. 60, iss. 1

art. no. 178149

EN

It is inevitable for the occurrence or built-ups of disturbing cations, especially Ca2+ or Mg2+ ions, in process water during the flotation of iron oxides by using starch as flocculants. In addition to alkali concentrations and temperature, water quality could have an essential role in changing the physicochemical properties of the starch solution and consequently disturbing its flocculation performance on particles. This study aims to identify the effects of magnesium ions on the gelatinization characteristics of starch and its flocculation properties on particles through a series of tests, such as flotation tests, settling tests, size analyses, zeta potentials, powder contact angle, Fourier Transform Infra-Red (FTIR) and X-ray Photoelectron Spectroscopy (XPS) measurement. All results show that magnesium ions at ≤ 4 mmol/L have a positive role due to enlarging the sizes of the particle flocs and accelerating their settling rates. The occurrence of Mg2+ ions at higher concentrations during starch gelatinization only obtains a starch sol-gel with entangled configurations and preoccupied active sites, resulting in the slower settling rate of the particle flocs and less hydrophilicity on mineral surfaces. It could be attributed to the cross-link interactions of magnesium-based precipitates with the acidic groups, especially carboxyl groups on the starch remnants. The suitable acid/base interactions between Mg(OH)2/MgCO3 compounds with these groups in the starch suspension could be beneficial for enhancing the flocculation of hematite as they could build bridges among the pieces and enlarge their sizes as a “load carrier” for aggregation with minerals. However, too much cross-linking could reentangle the remnants, block their adsorption sites on mineral surfaces, and eventually, weaken the flocculation capacity of starch.

2

Comparative investigation on capture characteristics of chalcopyrite and hematite in PHGMS process

Tao Mingyu, Chen Luzheng, Dai Pulin, Xue Zixing, Chen Hang

Physicochemical Problems of Mineral Processing

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2024

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Vol. 60, iss. 1

art. no. 185334

EN

Pulsating high-gradient magnetic separation (PHGMS) is a promising method of separating chalcopyrite from other minerals with similar floatability. However, the capture characteristics of chalcopyrite in the PHGMS process remain poorly understood. In this study, the difference in the capture capacity of chalcopyrite and hematite, a typical weak magnetic mineral, was theoretically compared. The effects of the key operating parameters, i.e., magnetic induction, slurry flow rate, and magnetic wire diameter, on the capture difference between chalcopyrite and hematite, were investigated through experimental verification. The comparison results showed that chalcopyrite shared a similar capture trend with hematite. The capture mass weight of the matrix decreased with an increase in the pulsating frequency, slurry flow rate, and magnetic wire diameter, but it increased with improved magnetic induction. However, chalcopyrite exhibited a smaller capture mass weight due to its lower susceptibility, which required a higher magnetic induction (1.4 T), slower flow rate (1.5 cm/s), lower pulsating frequency (150 rpm), and smaller matrix diameter (1 mm) for higher efficient recovery of chalcopyrite. As the magnetic induction increased from 0.8 T to 1.6 T, the chalcopyrite recovery improved from 65.84% to 75.80%. These findings provide valuable information for improving the utilization of chalcopyrite.

3

Classification techniques and parameter optimization of Cyclone Continuous Centrifugal Separator for hematite ore

Zhang Pei, Xie Haiyun, Jin Yanling, Chen Jialing, Zeng Peng, Li Yuanhong, Chen Luzheng, Liu Dianwen

Physicochemical Problems of Mineral Processing

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2023

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Vol. 59, iss. 1

art. no. 158864

EN

The Cyclonic Continuous Centrifugal Separator (CCCS) is a new type of separation equipment developed based on cyclonic continuous centrifugal separation technology and combined with the separation principle of the fluidized bed. Taking hematite as the research object, the main parameters and conditions of the best hematite classification were determined through the classification test by using CCCS. Based on the classification test, the significance order of each process parameter and their interaction with hematite classification efficiency of the underflow products was analyzed with the Response Surface Methodology, the optimal process parameter of hematite classification was obtained and a multiple regression equation was established. The optimized process conditions were as follows, feeding pressure 55.48 kPa, backwash pressure 9.79 kPa, and underflow pressure 31.94 kPa. Under these conditions, the average hematite ore classification efficiency of coarse fraction (-2~+0.15mm), medium fraction (-0.15~+0.074mm) and fine fraction (-0.074mm) were 85.08%, 65.10% and 51.41%, respectively, and the relative errors with the predicted values were 1.6%, 4.0% and 2.5%, respectively. The results showed that the analytical model has good predictive performance. This research provides a certain prospect for the application of Cyclonic Continuous Centrifugal Separation to hematite ore classification. it provides a reference for the application of the Response Surface Methodology in the classification of hematite by Cyclonic Continuous Centrifugal Separation.

4

Mineralogy characteristics, stability conditions, and formation pathways of synthetic pyrrhotite formed by heating pyrite at 700℃

Wang Zhehao, Wang Ling, He Yuting, Duan Jiongran, Fan Bowen

Gospodarka Surowcami Mineralnymi

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2023

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T. 39, z. 1

23--34

EN

Pyrite is a sulfide mineral and is widely distributed in nature. Pyrite may transform into pyrrhotite when heated at high temperatures. In order to support processing engineering techniques and industrial applications of pyrite and pyrrhotite, it is necessary to investigate synthetic pyrrhotite, which is formed by heating pyrite in air, based on existing research. In this work, the mineralogical characteristics and stability conditions of synthetic pyrrhotite formed by heating pyrite at elevated temperatures were studied. The possible formation pathway was verified using a solid-phase reaction. X-ray-diffraction results revealed that synthetic pyrrhotite differs from natural pyrrhotite in the paragenetic association of minerals. Natural pyrrhotite and magnetite coexist in the natural pyrrhotite sample. Synthetic pyrrhotite formed by heating pyrite at 700℃ for 1 h has the paragenetic association with hematite and a small amount of pyrite and magnetite. All pyrrhotite samples were monoclinic pyrrhotite-4C (Fe7S8) and exhibit minimal differences in terms of lattice parameters. Synthetic pyrrhotite-4C was stable under 0.5–2 h of heating at 700℃ in air. It had the highest relative content by heating for 1 h. It was eventually transformed into hematite with heating periods exceeding 3 h, as was the case for pyrite and magnetite. In air, synthetic pyrrhotite-4C is mainly formed via two pathways: (1) pyrite → pyrrhotite-4C and (2) pyrite → magnetite → pyrrhotite-4C. Pathway (1) is more favorable than pathway (2). This transformation cannot be achieved by the reaction between hematite and sulfur.

PL

Piryt jest minerałem siarczkowym szeroko rozpowszechnionym w przyrodzie. Piryt może przekształcić się w pirotyn podczas ogrzewania w wysokich temperaturach. W celu wsparcia technik inżynierii mineralnej i przemysłowego zastosowania pirytu i pirotynu, konieczne jest zbadanie syntetycznego pirotynu w oparciu o istniejące badania, który powstaje w wyniku ogrzewania pirytu w powietrzu. W pracy zbadano właściwości mineralogiczne i warunki trwałości syntetycznego pirotynu powstałego w wyniku ogrzewania pirytu w podwyższonej temperaturze. Możliwą ścieżkę powstawania zweryfikowano za pomocą reakcji w fazie stałej. Wyniki dyfrakcji rentgenowskiej ujawniły, że syntetyczny pirotyn różni się od naturalnego pirotynu w paragenetycznych asocjacjach minerałów. Naturalny pirotyn i magnetyt współistnieją w próbce naturalnego pirotynu. Syntetyczny pirotyn powstały w wyniku ogrzewania pirytu w temperaturze 700℃ przez 1 godz. wykazuje asocjację paragenetyczną z hematytem oraz niewielką ilością pirytu i magnetytu. Wszystkie próbki pirotynu były jednoskośnym pirotynem-4C (Fe7S8) i wykazują minimalne różnice pod względem parametrów sieci. Syntetyczny pirotyn-4C był stabilny w czasie 0,5–2 godzin ogrzewania w powietrzu w temperaturze 700℃. Najwyższą względną zawartość miał po ogrzewaniu przez 1 godzinę. Ostatecznie został przekształcony w hematyt z okresami ogrzewania przekraczającymi 3 godziny, podobnie jak w przypadku pirytu i magnetytu. W powietrzu syntetyczny pirotyn-4C powstaje głównie dwoma metodami: (1) piryt → pirotyn-4C i (2) piryt → magnetyt → pirotyn-4C. Ścieżka (1) jest korzystniejsza niż ścieżka (2). Tej przemiany nie można osiągnąć w reakcji hematytu z siarką.

5

A study of the influence of synthesis parameters on the physicochemical properties of iron pigments produced from waste iron sulfate

Splinter Kamila, Lendzion-Bieluń Zofia

Chemical and Process Engineering : New Frontiers

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2023

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Vol. 44, nr 2

art. no. e12

EN

The work presents a two-step method of iron red synthesis based on waste iron(II) sulfate. The synthesis was carried out using purified waste iron sulfate from titanium dioxide production. The study investigated the influence of factors such as temperature, pressure, concentration of solutions and synthesis time on the physicochemical properties of pigments. Obtained pigments were tested by instrumental analytical methods, e.g. X-ray Diffraction or BET surface area analysis. The pigments were analyzed for color, praticles size as well as for oil number. The results of the research showed a change in the physicochemical properties of the obtained pigments depending on the conditions of synthesis. It was shown that increasing the synthesis time in most cases increased the degree of crystallization of hematite in the pigments. High specific surface area, low agglomeration of pigments or low oil absorption are directly related to the crystallinity of the pigments obtained. Laboratory pigments have been found to be different from commercial pigments. The difference in properties speaks in favor of synthesized materials.

6

Removing iron impurities from feldspar ore using dry magnetic separation (part one)

Yassin Khaled, Ahmed Mahmoud, Khalifa Mohamed Gamal Eldin Khalifa, Hagrass Ayman Aly

Archives of Mining Sciences

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2023

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Vol. 68, no. 1

19--33

EN

Feldspar is a basic requirement for glass, ceramics, and other industries. The presence of iron in feldspar is one of the challenging aspects of feldspar processing. To improve the quality of feldspar for use in various industries, dry magnetic separation is one of the best techniques for reducing iron in feldspar, especially in arid regions to overcome the common problem of lack of water resources as well as to reduce the operational cost of the enrichment process. Therefore, dry magnetic separation experiments were carried out to remove the iron content from feldspar ore in the Wadi Umm Harjal area in Egypt to meet the specifications required for different industries. The sample was analysed using XRD, XRF, and optical microscopy, which revealed that it is a mixture of potassium feldspar (microcline/orthoclase), albite, and quartz in the presence of hematite mineral serving as the main iron impurities in addition to the free silica content. The effect of parameters on the activity of the dry high magnetic separators was investigated in addition to cleaning the products. The iron oxide reduced from 0.69% in the head sample to 0.08% after dry high-intensity magnetic separation, and the whiteness increased from 82.01% in the head sample to 95.97% in the separated concentrate. The experimental results showed that there is a possibility to obtain feldspar concentrates with low content of Fe2O3 from the area where according to the results, approximately 88.4% of iron was removed from the head sample.

7

Study of recycling blast furnace dust by magnetization roasting with straw charcoal as reductant

Ju Jinrong, Feng Yali, Li Haoran, Zhang Qian

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 3

art. no. 149265

EN

Blast furnace dust generated in the iron-making process not only contains a large amount of iron but also the widely used non-ferrous metal zinc, which is classified as hazardous waste. In this study, the process of recycling blast furnace dust by magnetization roasting with straw charcoal as the reductant is proposed, and the mechanism of magnetization roasting was explored through thermodynamic analysis, X-ray diffraction analysis, and thermogravimetric analysis. The results for the thermodynamic analysis showed that the reduction of blast furnace dust by the straw charcoal was feasible theoretically. The increase in the roasting temperature not only promoted the reduction of hematite (Fe2O3) but also reduced zinc ferrite (ZnFe2O4) to Fe3O4 and ZnO. The results showed that almost all Fe2O3 and ZnFe2O4 in the blast furnace dust were reduced to Fe3O4 and ZnO under the conditions of straw charcoal amount of 6%, the roasting temperature of 750℃, and the roasting time of 60 min. Then, the iron concentrate with the iron recovery of 85.61% and an iron grade of 63.50% was obtained by the magnetic separation. Meanwhile, the grade of zinc in the iron concentrate was 0.19%. Finally, the flowsheet of simultaneously recovering iron and zinc from the blast furnace dust was put forward, which could realize that 85.61% of iron was recovered and 92.57% of zinc was extracted into the solution.

8

Enhanced effect of fine magnetite on the flotation performance of fine hematite in sodium oleate system

Pei Bin, Luo Ximei, Yang Wen, Wei Dayong, Li Chao, Wang Yunfan

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 4

art. no. 149673

EN

In this work, the effect of magnetite with different particle sizes on the flotation performance of both coarse and fine hematite particles were investigated by using sodium oleate as a collector. The results showed that the magnetite particles with different particle sizes showed a negative effect on hematite (-106+45 μm) recovery, but the addition of magnetite with the same particle sizes as hematite during the direct flotation of -45 μm hematite was beneficial to improve the recovery of micro-fine hematite and the Fe grade of concentrate. The finer the magnetite particle was, the more obvious the agglomeration effect of hematite was. Therefore, the beneficial effect could be achieved by adjusting the particle sizes of particles. Moreover, sodium oleate was beneficial to promote the agglomeration of micro-fine magnetite and hematite. The results from the microscopic analysis, laser particle size analysis, and EDLVO calculation proved that there was an effective aggregation between fine magnetite and fine hematite particles, which increased the apparent size of hematite particles and the probability of the mineral particles adhering to bubbles, thus improving the hematite recovery.

9

Physicochemical study and application for pyrolusite separation from high manganese-iron ore in the presence of microorganisms

Farghaly Mohamed Galal, Abdel-Khalek Nagui Aly, Abdel-Khalek Mohamed Abdel-Dayem, Selim Khaled Abdelaal, Abdullah Samah Saleh

Physicochemical Problems of Mineral Processing

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2021

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Vol. 57, iss. 1

273--283

EN

Paenibacillus polymyxa bacteria strain as a surface modifier in a flotation process could remove 64.89% of MnO2 from high manganese iron ore. A concentrate containing 3.7% MnO2, 0.5% SiO2 and 71.30% Fe2O3, with a hematite recovery of 72.46% is produced from a feed containing 8.79% MnO2, 0.49% SiO2 and 67.90% Fe2O3. The bio-flotation results indicated that such type of bacteria is selective for upgrading El-Gedida iron ore from the Western Desert of Egypt. The role of Paenibacillus polymyxa on the surface properties of pyrolusite and hematite single minerals was investigated through zeta potential, FTIR and adsorption measurements.

10

Comparison the Adsorption Capacity of Ukrainian Tuff and Basalt with Zeolite–Manganese Removal from Water Solution

Trach Yuliia, Tytkowska-Owerko Marta, Reczek Lidia, Michel Magdalena M.

Journal of Ecological Engineering

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2021

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Vol. 22, nr 3

161--168

EN

Manganese is an undesirable element in tap water but is common in the groundwater. Several methods can be used for manganese removal, including adsorption. Mined rocks are commonly evaluated as adsorbents and it was the objective of this paper – to investigate the Ukrainian volcanic tuff and basaltic rock from the Ivanodolinsky quarry and compare it with Ukrainian zeolite as well as with literature data. The research was based on equilibrated batch tests at a temperature of 10°C and slightly acidic pH. The data were treated using Langmuir and Freundlich models in the linear form. The results indicated the spontaneous and favourable adsorption of manganese. The volcanic tuff was characterized by the highest adsorption capacity, twice higher than basalt and zeolite. The heterogeneity of the active adsorption sites on the tuff was also greater and resulted from the diversity of the mineral composition. Considering the literature data, the properties of tuff are worth further research.

11

Równoczesne tłumienie promieniowania gamma i neutronów w jednowarstwowej osłonie betonowej

Safamehr Majid, Izadinia Mohsen, Hashemi Seyed Hamid, Hoseini Seyed Jalil

Cement Wapno Beton

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2021

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R. 26, nr 6

503--514

PL

Dzięki możliwości zastosowania różnych połączeń, beton jest jednym z najbardziej odpowiednich materiałów do konstruowania osłon przed promieniowaniem. W niniejszych badaniach kruszywo hematytowe i magnetytowe zastąpiło kruszywo zwykłe, oddzielnie i całkowicie w dwóch etapach. Dodatkowo zastępowano 2,5, 5 i 10% masowych cementu węglikiem boru. Przeprowadzono badanie gęstości, tłumienia promieniowania gamma z użyciem źródła Co 60 i promieniowania neutronowego z użyciem Am-Be 241. Zgodnie z wynikami, zastąpienie kruszywa zwykłego kruszywem hematytowym, poprawiło liniowy współczynnik tłumienia i makroskopowy przekrój czynny absorpcji neutronów betonu odpowiednio o 17% i 73%. Właściwości te poprawiły się odpowiednio o 37% i 105%, przy zastosowaniu kruszywa magnetytowego. Ponadto, przy dodaniu do składu betonu maksymalnie 10% węglika boru, makroskopowy przekrój czyny wzrósł o 120%, jednak liniowy współczynnik tłumienia zmniejszył się tylko o 5-8%. Oznacza to, że możliwe jest uzyskanie odpowiedniego tłumienia promieniowania gamma i wiązek neutronów jednocześnie, w jednej warstwie betonowej osłony. Ponadto stwierdzono dobrą zgodność wyników badań i symulacji Monte Carlo.

EN

The ability to create various compounds has made concrete one of the most suitable materials for constructing radiation shields. In this investigation, hematite and magnetite aggregates were used to replace ordinary aggregate, separately and completely in two stages. Boron carbide was also substituting cement at percentages of 2.5, 5, and 10 by mass. The density test, gamma irradiation with Co 60 and neutron irradiation with Am-Be 241 were performed. According to the results, the replacement of ordinary aggregates with hematite aggregates in concrete, improved the linear attenuation coefficient and macroscopic cross section by 17% and 73%, respectively. These parameters increased by 37% and 105%, respectively, by the use of magnetite aggregates. Moreover, with the addition of a maximum of 10% boron carbide to the concrete, the macroscopic cross-section increased by 120%, however, the linear attenuation coefficient decreased by between 5% and 8%. This means that it is possible to have a suitable attenuation of gamma ray and neutron beams in a single layer of concrete shield simultaneously. In addition, the results of the tests and Monte Carlo simulation were found to have good consistency.

12

Rola nanokrzemionki w betonie zawierającym kruszywo hematytowe i magnetytowe oraz węglik boru jako osłony przed promieniowaniem gamma

Safamehr Majid, Izadinia Mohsen, Hashemi Seyed Hamid, Koohestani Saeideh

Cement Wapno Beton

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2021

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R. 26, nr 3

218--232

PL

W artykule opisano wyniki badań dwóch betonów ciężkich, pierwszy zawierający kruszywo hematytowe i drugi magnetytowe. Węglik boru wprowadzono jako zamiennik cementu w ilościach 2,5; 5 i 10% masowych. Następnie w tych mieszankach ilość cementu zmniejszono o 5% i zastąpiono nanokrzemionką. Zbadano także właściwości betonu: wytrzymałość na ściskanie, szybkość przejścia fali ultradźwiękowej i gęstość, a także napromieniowano próbki kobaltem 60, w celu określenia współczynnika tłumienia liniowego. Zastosowanie kruszyw zawierających tlenek żelaza, a zwłaszcza magnetyt, było korzystne dla wszystkich wymienionych właściwości, natomiast odwrotnie było w przypadku dodania do mieszanki węglika boru. Dodatek nanokrzemionki skompensował spadek wytrzymałości betonu na ściskanie spowodowany dodatkiem węglika boru, ale zmniejszył współczynnik tłumienia liniowego o około 4%. Jednak właściwości mieszanek zawierających węglik boru i nanokrzemionkę były zawsze lepsze niż w przypadku betonów zwykłych. W celu określenia współczynnika tłumienia liniowego przeprowadzono symulacje Monte Carlo, których wyniki okazały się zgodne z wynikami uzyskanymi w trakcie badań doświadczalnych.

EN

Two families of heavy concrete were investigated in this project, the first containing hematite and the second magnetite aggregates. Boron carbide also replaced cement in mass of 2.5, 5 and 10%. Once again, in these compounds the content of cement was reduced by 5% and replaced by nanosilica. Such parameters as compressive strength, ultrasonic pulse velocity and density were investigated, and the specimens were irradiated with cobalt 60, to quantify the linear attenuation coefficient. Using iron ore aggregate, especially magnetite, was advantageous for all the above-mentioned parameters, while the opposite was true, when boron carbide was added to the mix. The addition of nanosilica compensated the decrease in compressive strength of concrete due to the presence of boron carbide, but reduced the linear attenuation coefficient by about 4%. However, the properties of the mixes containing boron carbide and nanosilica, were always better than those of conventional concretes. To quantify the linear attenuation coefficient, Monte Carlo simulations were performed, and their results turned out to be in good agreement with those obtained by the experimental measurements.

13

Study of N, N-bis (2-hydroxyethyl) -N-methyl dodecyl ammonium chloride as the novel collector in selective flotation separation of quartz and hematite

Liu Wenbao, Liu Wengang, Zhao Qiang, Wang Xinyang, Duan Hao, Peng Xiangyu, Wang Benying

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 2

286--299

EN

A quaternary ammonium salt, N, N-bis (2-hydroxyethyl)-N-methyl dodecyl ammonium chloride (BHMDC), with high surface activity, was screened and firstly introduced in the reverse flotation of hematite ores based on Density Functional Theory (DFT) calculation and surface tension measurement. The interaction mechanism of BHMDC on the surfaces of quartz and hematite was studied by zeta potential measurement, X-ray photoelectron spectroscopy (XPS) and Fourier transforms infrared spectroscopy (FTIR), respectively. The results of DFT calculation and surface tension measurement indicated that BHMDC had higher selectivity and hydrophobicity than dodecylamine (DDA). The analyses of zeta potential measurement, FTIR, and XPS demonstrated that the adsorption of BHMDC on hematite and quartz surfaces were mainly dependent on hydrogen bonding and electrostatic interaction. Due to the more active sites (O atoms), the weaker charge and larger size of polar groups, BHMDC had better simulation results in performance than DDA, especially in selectivity. The flotation tests showed that BHMDC exhibited better flotation performance, which was consistent with the results of DFT calculation. And the efficient separation of hematite and quartz within the wide pH value range (4.0-10.0) was determined, which was also confirmed by zeta potential measurement. It also indicated that BHMDC was an excellent collector in the reverse flotation of hematite ores with great industrial potential, which could obtain the concentrate with the Fe grade of 65.37% and recovery of 88.92%

14

Effect of particle size on reduction kinetics of hematite ore in suspension roaster

Gaob Peng, An Yaxiong, Li Guofeng, Han Yuexin

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 3

449--459

EN

Suspension magnetization roasting followed by magnetic separation is an innovative and effective way to recover iron from refractory iron ores, and the particle size of the ore greatly affects the roasting index. To identify the effect of particle size on the reduction kinetics for the transformation of hematite to magnetite, a high-purity hematite ore with different size fractions were isothermally reduced using a suspension roaster. The pure hematite ore was divided into -1000+500 µm, -500+150 µm, -150+74 µm, -74+37 µm and -37 µm size fractions, while the gas mixture of CO and CO2 with a volume ratio of 1:4 was used as reductant. The results showed that the most suitable mechanism function for the reduction of -37 µm size fraction hematite ore is the Avrami-Erofeev model. In the case of -500+37 µm size fraction, the reduction process can be described by first-order chemical reaction model. For -1000+500 µm size fraction, the reduction of hematite ore is restricted by the second-order chemical reaction. In addition, scanning electron microscopy (SEM) analysis results demonstrated that the transformation of hematite particles to magnetite is in accordance with the characteristics of shrinking core model. The phase transformation primarily occurs at the edge of hematite particles and then develop towards the inner side of particles. The findings of this paper provide a theoretical basis for the development and utilization of refractory hematite ore via suspension magnetization roasting technology.

15

Enhanced visible light absorption of shape-controlled TiO2@Fe2O3 composites

Synowiec Milena, Zazakowny Karolina

Composites Theory and Practice

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2020

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R. 20, nr 3-4

157--162

EN

This article presents titanium(IV) oxide nanocrystals in the crystalline form of anatase obtained by hydrothermal synthesis using various shape-controlling agents. Two methods were applied. In the first, diethanolamine (DEA) was used as the shape-controlling agent and titanium(IV) isopropoxide (TTIP) as the TiO2 precursor. In the second method, carbonate ions were responsible for controlling the shape, while potassium titanate nanowires (KTNWs) were the precursor of TiO2. The expected application of the nanocrystals was related to the absorption of visible light. Therefore, the main goal was to modify shape-controlled TiO2 with a narrow band semiconductor providing absorption of light in that range. Based on spectrophotometric analysis, it was found that the TiO2@Fe2O3 composites possess a band gap in the range between 2.21 and 2.30 eV which originates from the Fe2O3 nanoparticles. Moreover, a small amount of Fe3+ ions was incorporated into the TiO2 lattice, as evidenced by the band gap ranging from 2.85 to 2.95 eV.

PL

Przedstawiono nanokryształy dwutlenku tytanu w postaci anatazu otrzymane w wyniku syntezy hydrotermalnej przy zastosowaniu różnych środków kontroli kształtu. W pierwszej metodzie użyto dietanoloaminy (DEA) jako środka regulującego kształt i izopropanolanu tytanu(IV) (TTIP) jako prekursora TiO2. W drugiej metodzie za kontrolę kształtu odpowiadały jony węglanowe, a prekursorem były nanodruty tytanianu potasu (KTNWs). Mając na uwadze przyszłe wykorzystanie otrzymanych nanokryształów w zastosowaniach związanych z absorpcją światła widzialnego, celem było zmodyfikowanie TiO2 o kontrolowanym kształcie za pomocą półprzewodnika wąskopasmowego, którego absorpcja promieniowania obejmuje obszar widzialny. Uzyskane kompozyty TiO2@Fe2O3 posiadają przerwę wzbronioną o wartości z przedziału od 2,21 do 2,30 eV pochodzącą od nanocząstek Fe2O3. Ponadto niewielka ilość jonów Fe3+ została wprowadzona do sieci TiO2, o czym świadczy przerwa wzbroniona o wartości 2,85÷2,95 eV.

16

Investigations on soluble starch as the depressant of hematite during flotation separation of apatite

Bai Shaojun, Ding Zhan, Fu Xianyu, Li Chunlong, Lv Chao, Wen Chao

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 1

38--48

EN

In this paper, soluble starch was studied as a depressant of hematite during flotation separation of apatite using sodium oleate as a collector. Surface charge measurement, soluble starch adsorptions, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to understand the interaction mechanisms between minerals (hematite and apatite) and soluble starch. The results indicated that chemical interaction between hematite and soluble starch was present, and supported the bonding of hydroxyl, while physical adsorption of soluble starch molecules with apatite occurred. Results of micro-flotation studies suggested that soluble starch was considered as a selective depressant for hematite. The maximum recovery difference between hematite and apatite of 77.5% was obtained with 40 mg/dm3 soluble starch. The flotation experiment results of natural iron ore showed that flotation indexes with 59.73% Fe, iron recovery of 81.5% and 75.68% of dephosphorization ratio were achieved at a soluble starch dosage of 60 mg/dm3. However, a higher dosage of soluble starch addition caused the difficulty for flotation separation of apatite from hematite. Our results provided theoretical basis for the flotation separation of apatite from iron oxide ores.

17

Effect of particle size on flotation performance of hematite

Luo Ximei, Song Shuixiang, Ma Mingze, Wang Yunfan, Zhou Yongfeng, Zhang Ying

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 2

479--493

EN

The effect of particle size on flotation performance of hematite and quartz was investigated. Microflotation, X-ray photoelectron spectroscopy analysis, reagent adsorption measurements, and collision and attachment probability calculation between particle and bubble were conducted in this investigation. The results showed that the floatability of minerals with different particle size fractions was different, which was mainly related to surface bonding site, reagent adsorption, collision probability and entrainment. The quartz with different particle size had little impact on hematite recovery, but -45 μm fraction negatively affected Fe grade of concentrate both in the direct and reverse flotation of hematite. In the direct flotation, the Fe grade in froth product dropped off due to the fine quartz entrainment. While in the reverse flotation, the Fe grade in sink product dropped off as a result of difficulty in floating fine quartz particles, which was due to lower collision probability. Meanwhile, in the reverse flotation, the presence of hematite fines (-18 μm fraction) also had negative impact on hematite recovery because of fine particle entrainment.

18

Effect of fluidized magnetizing roasting on iron recovery and transformation of weakly magnetic iron mineral phasein iron tailings

Li Wenbo, Han Yuexin, Liu Xiao, Shan Yan, Li Yanjun

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 4

906--916

EN

The eastern tailings of the Anshan mining area are generally categorized as high silicon-bearing iron tailings, and the iron mainly exists in the form of hematite–limonite with an iron grade of 10.60%. In order to recover iron minerals and reduce the influence of the tailings on the environment, a method for pre-enrichment through the combination of low intensity magnetic separation and high intensity magnetic separation with fluidized magnetizing roasting and subsequent low intensity magnetic separation was developed to treat the eastern tailings of the Anshan mining area. The effects of gas-flow rate, H2 concentration, roasting temperature, and roasting time on the quality of the final iron concentrate were discussed. Moreover, the iron phase transformation and change in magnetism of the sample were studied. The results indicated that an iron concentrate with an iron grade of 65.30% and a recovery of 85.85% could be obtained under the conditions of gas-flow rate of 8 m3/h, H2 concentration of 50%, and fluidized magnetizing roasting at 600 ℃ for 20 s. X-ray diffraction analysis, phase analysis, and magnetism analysis on the roasted materials indicated that the hematite–limonite could be transformed into magnetite during the fluidized magnetizing roasting process, and effective separation of iron and gangues could be easily achieved by the weak magnetic separation.

19

Effect and mechanism of citric acid on flotation separation of siderite and hematite

Han Huili, Yin Wanzhong, Yao Jin, Li Dong

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 1

311--323

EN

Heterocoagulation can occur between fine siderite and hematite particles, which would result in the low efficiency of their separation during the flotation process. To date, there have been no mature methods to increase their separation efficiency. In this paper, citric acid was used as a regulator to enhance the slurry dispersion efficiency. Micro-flotation, scanning electron microscopy (SEM) analysis, settling tests, particle size measurements, zeta potential measurements and E-DLVO theoretical calculations were conducted in the investigations. A maximum recovery difference (53.98%) between siderite and hematite in their mixtures flotation was obtained. Settling tests confirmed that citric acid contributed to improving the dispersion degree of the slurry. SEM analysis indicated that citric acid could clean the surface of particles and weaken the coagulation between siderite and hematite, which were in line with the results of particle size measurements. The zeta potential measurements and Extended-Derjaguin-Landau-Verwey-Overbeek (E-DLVO) theoretical calculations indicated that the citric acid could adsorb on the siderite and hematite surfaces and decreased the surface charge, resulting in a visible increase of the repulsion energy between siderite and hematite particles. Therefore, citric acid can be applied to remove the easily-ground carbonate minerals first to improve the flotation performance of hematite in the separation process of carbonate-containing iron ores.

20

Analysis of crystallite size changes in a hematite and magnetite formed on steel used in the power idustry

Gwoździk M.

Technical Sciences / University of Warmia and Mazury in Olsztyn

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2018

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nr 21(1)

65--73

EN

The paper presents results of studies on the crystallite sizes of oxide layer formed during a long-term operation on 10CrMo9-10 steel at an elevated temperature (T = 545° C, t = 200,000 h). This value was determined by a method based on analysis of the diffraction line profile, according to a Scherrer formula. The oxide layer was studied on a surface and a cross-section at the outer and inner site on the pipe outlet, at the fire and counter-fire wall of the tube. X-ray studies were carried out on the surface of a tube, then the layer’s surface was polished and the diffraction measurements repeated to reveal differences in the originated oxides layer.