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Iron recovery from copper slag generated during copper production by the pyrometallurgical method has been widely investigated to achieve resource utilisation. Liberation and enrichment of metallic iron from reductively roasted copper slag were explored in this work. Results show that metallic iron, quartz solid solution, and cristobalite solid solution are the main phases in reductively roasted copper slag, and most metallic iron particles are wrapped by silica. A concentrate with 74.39% Fe content and 83.14% Fe recovery is obtained through grinding–magnetic separation. For comparison, the metallic iron particles are liberated through alkali leaching of silica. The Fe content in leaching residue reaches 78.17% by removing 88.96% SiO2 and further increases to 90.45% by magnetic separation with Fe recovery of 85.20%. Therefore, alkali leaching–magnetic separation is suitable for treating reductively roasted copper slag because of the high Fe content in concentrate and comprehensive recovery of silica. (Authors.), Iron recovery from copper slag generated during copper production by the pyrometallurgical method has been widely investigated to achieve resource utilisation. Liberation and enrichment of metallic iron from reductively roasted copper slag were explored in this work. Results show that metallic iron, quartz solid solution, and cristobalite solid solution are the main phases in reductively roasted copper slag, and most metallic iron particles are wrapped by silica. A concentrate with 74.39% Fe content and 83.14% Fe recovery is obtained through grinding–magnetic separation. For comparison, the metallic iron particles are liberated through alkali leaching of silica. The Fe content in leaching residue reaches 78.17% by removing 88.96% SiO2 and further increases to 90.45% by magnetic separation with Fe recovery of 85.20%. Therefore, alkali leaching–magnetic separation is suitable for treating reductively roasted copper slag because of the high Fe content in concentrate and comprehensive recovery of silica. (Authors.)

For every ton of pyrometallurgical Cu 2-3 t of Cu slag are generated, amounting globally to 4 000 000-5 000 000 t/a containing 35-45% Fe and 25-35% SiO2. An isothermal study of the solid-state reduction kinetics of fayalite with and without the addition of 10 wt% metallic Fe found that the carbothermal reduction is controlled by phase boundary reaction and that adding Fe decreases the activation energy from 165.22 to 145.74 kJ/mol. The fayalite decomposes into metallic Fe and quartz solid solution, the latter being converted into cristobalite solid solution with increasing temperature. The addition of metallic Fe creates a nucleating effect that accelerates the decomposition., For every ton of pyrometallurgical Cu 2-3 t of Cu slag are generated, amounting globally to 4 000 000-5 000 000 t/a containing 35-45% Fe and 25-35% SiO2. An isothermal study of the solid-state reduction kinetics of fayalite with and without the addition of 10 wt% metallic Fe found that the carbothermal reduction is controlled by phase boundary reaction and that adding Fe decreases the activation energy from 165.22 to 145.74 kJ/mol. The fayalite decomposes into metallic Fe and quartz solid solution, the latter being converted into cristobalite solid solution with increasing temperature. The addition of metallic Fe creates a nucleating effect that accelerates the decomposition.

The activation mechanism of Pb(II) on the flotation of wolframite was systematically investigated. Micro-flotation test results showed that Pb(II) effectively improved the flotation of wolframite in the presence of benzyl hydroxamic acid (BHA). Maximum floatability of wolframite was achieved at approximately pH 8.5. Adsorption of the hydrolyzed species of Pb(II) occurred at this pH value, which provided more activated sites on the wolframite surface. As such, BHA-Pb complexes were formed on the wolframite surface, which increased the BHA adsorption. In addition, BHA-Pb complexes were also formed in solution, which replaced the Fe and interacted with the Mn on the wolframite surface. These findings were proved by the results of zeta-potential measurements, adsorption measurements, solution chemistry calculations, Fourier transform infrared spectroscopy (FTIR) analysis, and X-ray photoelectron spectroscopy (XPS) characterization.

The results of experiments on examples of a hydrophobic, a sulphide and an oxide mineral showed that the presence of sufficient amount of colloidal montmorillonite clay particles in the mineral slurry would be detrimental to flotation by reducing mineral recovery. This observation was attributed to a slime coating of clay on the coarse valuable mineral particles and entrainment of clay particles in the froth product together with water in the triangle froth zones. The former would reduce the recovery of the valuable minerals because of the hydrophilic nature of the coating, while the latter would decrease the concentrate grade. The degree of slime coating depended on slurry pH while the degree of entrainment was closely related to water recovery. It was also found that slime coating was a dominant factor in mineral flotation in acidic pH regions in the presence of colloidal montmorillonite particles., The results of experiments on examples of a hydrophobic, a sulphide and an oxide mineral showed that the presence of sufficient amount of colloidal montmorillonite clay particles in the mineral slurry would be detrimental to flotation by reducing mineral recovery. This observation was attributed to a slime coating of clay on the coarse valuable mineral particles and entrainment of clay particles in the froth product together with water in the triangle froth zones. The former would reduce the recovery of the valuable minerals because of the hydrophilic nature of the coating, while the latter would decrease the concentrate grade. The degree of slime coating depended on slurry pH while the degree of entrainment was closely related to water recovery. It was also found that slime coating was a dominant factor in mineral flotation in acidic pH regions in the presence of colloidal montmorillonite particles.

Heavy metals usually referred to those with atomic weights ranging from 63.5 to 200.6. Because of natural-mineral dissolution and human activities such as mining, pesticides, fertilizer, metal planting and batteries manufacture, etc., these heavy metals, including zinc, copper, mercury, lead, cadmium and chromium have been excessively released into water courses, like underground water, lake and river, etc. The ingestion of the heavy metals-contaminated water would raise serious health problems to human beings even at a low concentration. For instance, lead can bring human beings about barrier to the normal function of kidney, liver and reproductive system, while zinc can cause stomach cramps, skin irritations, vomiting and anemia. Mercury is a horrible neurotoxin that may result in damages to the central nervous system, dysfunction of pulmonary and kidney, chest and dyspnea. Chromium (VI) has been proved can cause many diseases ranging from general skin irritation to severe lung carcinoma. Accordingly, the World Health Organization announced the maximum contaminant levels (MCL) for the heavy metals in drinking water. There are numerous processes for eliminating heavy metals from water in order to provide citizens safe drinking water, including precipitation, adsorption, ion exchange, membrane separation and biological treatment, etc. Adsorption is considered as a potential process for deeply removing heavy metals, in which the selection of adsorbents plays a predominant role.Nano-sheet minerals as the adsorbents are currently the hottest researches in the field. They are obtained from layered minerals, such as montmorillonite, graphite and molybdenite, through the processing of intercalation, electrochemical and mechanical exfoliation, etc. Nano-sheet minerals are featured by their large specific surface area, relatively low costs and active adsorbing sites, leading to be effective and potential adsorbents for heavy metals removal from water.Montmorillonite was usu

Heavy metals usually referred to those with atomic weights ranging from 63.5 to 200.6. Because of natural-mineral dissolution and human activities such as mining, pesticides, fertilizer, metal planting and batteries manufacture, etc., these heavy metals, including zinc, copper, mercury, lead, cadmium and chromium have been excessively released into water courses, like underground water, lake and river, etc. The ingestion of the heavy metals-contaminated water would raise serious health problems to human beings even at a low concentration. For instance, lead can bring human beings about barrier to the normal function of kidney, liver and reproductive system, while zinc can cause stomach cramps, skin irritations, vomiting and anemia. Mercury is a horrible neurotoxin that may result in damages to the central nervous system, dysfunction of pulmonary and kidney, chest and dyspnea. Chromium (VI) has been proved can cause many diseases ranging from general skin irritation to severe lung carcinoma. Accordingly, the World Health Organization announced the maximum contaminant levels (MCL) for the heavy metals in drinking water. There are numerous processes for eliminating heavy metals from water in order to provide citizens safe drinking water, including precipitation, adsorption, ion exchange, membrane separation and biological treatment, etc. Adsorption is considered as a potential process for deeply removing heavy metals, in which the selection of adsorbents plays a predominant role.Nano-sheet minerals as the adsorbents are currently the hottest researches in the field. They are obtained from layered minerals, such as montmorillonite, graphite and molybdenite, through the processing of intercalation, electrochemical and mechanical exfoliation, etc. Nano-sheet minerals are featured by their large specific surface area, relatively low costs and active adsorbing sites, leading to be effective and potential adsorbents for heavy metals removal from water.Montmorillonite was usu

Molybdenite (MoS2) is predominantly recovered from the flotation of copper porphyric ores, which is carried out at a high pH and achieved with lime, which supplies Ca ions to the flotation pulp. MoS2 is selectively floated from the Cu-MoS2 bulk concentrate while depressing the Cu minerals. In the Cu ore flotation circuit, the Cu recovery is high, but that of MoS2 is low. To delineate the loss of the MoS2 natural floatability and low recovery, the characteristics of the hydrophobic face of pristine MoS2 particles have been studied through atomic force microscopy, which revealed that the face is made up of microcrystals of MoS2 having well defined nano-edges and faces. The nano-edges render hydrophilic the faces of molybdenite particles and seem to be responsible for the low natural floatability of MoS2, the adsorption of Ca ions on MoS2 faces and the decrease of this natural floatability by Ca ions at a high pH. Both hydrophobic and hydrophilic surface fractions on the face have been determined using contact angle values determined by the captive bubble and Washburn capillary penetration methods. It was found that the hydrophobic surface fraction is only about 50%. The effect of pH and Ca ions on the natural floatability of various size fractions of MoS2 particles is presented in this study., Molybdenite (MoS2) is predominantly recovered from the flotation of copper porphyric ores, which is carried out at a high pH and achieved with lime, which supplies Ca ions to the flotation pulp. MoS2 is selectively floated from the Cu-MoS2 bulk concentrate while depressing the Cu minerals. In the Cu ore flotation circuit, the Cu recovery is high, but that of MoS2 is low. To delineate the loss of the MoS2 natural floatability and low recovery, the characteristics of the hydrophobic face of pristine MoS2 particles have been studied through atomic force microscopy, which revealed that the face is made up of microcrystals of MoS2 having well defined nano-edges and faces. The nano-edges render hydrophilic the faces of molybdenite particles and seem to be responsible for the low natural floatability of MoS2, the adsorption of Ca ions on MoS2 faces and the decrease of this natural floatability by Ca ions at a high pH. Both hydrophobic and hydrophilic surface fractions on the face have been determined using contact angle values determined by the captive bubble and Washburn capillary penetration methods. It was found that the hydrophobic surface fraction is only about 50%. The effect of pH and Ca ions on the natural floatability of various size fractions of MoS2 particles is presented in this study.

Ammoniacal copper(II) solution activated high-iron marmatite (sphalerite) particles in flotation better than the traditional activator, copper sulphate. Xanthate was the collector., Ammoniacal copper(II) solution activated high-iron marmatite (sphalerite) particles in flotation better than the traditional activator, copper sulphate. Xanthate was the collector.

The calculated potential energies of interaction between hydrophobic particles of three minerals (rhodochrosite, quartz and talc) and air bubbles show that hydrophobic interaction, rather than heterocoagulation, is the dominant factor in bubble attachment. A unified attachment rate equation for particle-bubble collision and adhesion in turbulent flow, invoking the concept of "capture efficiency" based on an energy barrier for capture, is proposed. It was found that the hydrophobic bubble-particle aggregates can be detached in the impeller zone, whereas no detachment occurs in the bulk zone, particularly for coarser particles. An expression for the flotation rate constant derived from the probabilities of collision, adhesion and detachment is derived and verified experimentally., The calculated potential energies of interaction between hydrophobic particles of three minerals (rhodochrosite, quartz and talc) and air bubbles show that hydrophobic interaction, rather than heterocoagulation, is the dominant factor in bubble attachment. A unified attachment rate equation for particle-bubble collision and adhesion in turbulent flow, invoking the concept of "capture efficiency" based on an energy barrier for capture, is proposed. It was found that the hydrophobic bubble-particle aggregates can be detached in the impeller zone, whereas no detachment occurs in the bulk zone, particularly for coarser particles. An expression for the flotation rate constant derived from the probabilities of collision, adhesion and detachment is derived and verified experimentally.

Since human daily demands for fresh water have been increased significantly, the supply of fresh water for the mining industry, especially froth flotation, should be considerably reduced. In addition, stricter environmental standards have been implemented in many countries to reduce the risks due to the disposal of wastewater, many flotation operators have to seek more efficient ways to utilise the limited fresh water sources. Recycling water with high concentrations of impurities is a normal strategy for most of the mineral processing plants; however, water quality should be carefully considered to guarantee a smooth flotation process. Recently, the application of seawater in flotation has attracted much attention due to its availability and abundance rather than fresh water. However, the influencing mechanisms due to the application of seawater in flotation have not been fully understood especially the reactions between mineral particles and bubbles in the presence of high concentrations of cations and anions. This would impede the application of alternatives to fresh water in the flotation. Therefore, this paper reviews the current water sources and the technologies for water recycling in the flotation process. Specifically, the life cycle of water in flotation was proposed. In addition, the strategies including high pulp density flotation as well as the most promising alternatives to fresh water have been discussed in details, with the related mechanisms being demonstrated. (Authors.), Since human daily demands for fresh water have been increased significantly, the supply of fresh water for the mining industry, especially froth flotation, should be considerably reduced. In addition, stricter environmental standards have been implemented in many countries to reduce the risks due to the disposal of wastewater, many flotation operators have to seek more efficient ways to utilise the limited fresh water sources. Recycling water with high concentrations of impurities is a normal strategy for most of the mineral processing plants; however, water quality should be carefully considered to guarantee a smooth flotation process. Recently, the application of seawater in flotation has attracted much attention due to its availability and abundance rather than fresh water. However, the influencing mechanisms due to the application of seawater in flotation have not been fully understood especially the reactions between mineral particles and bubbles in the presence of high concentrations of cations and anions. This would impede the application of alternatives to fresh water in the flotation. Therefore, this paper reviews the current water sources and the technologies for water recycling in the flotation process. Specifically, the life cycle of water in flotation was proposed. In addition, the strategies including high pulp density flotation as well as the most promising alternatives to fresh water have been discussed in details, with the related mechanisms being demonstrated. (Authors.)

The Ezhou pelletisation plant of Baowu, in China, with production capacity of 5 000 000 ton oxide pellets per year has the biggest single production line of grate-kiln ring cooler, provided by the Metso Company. The iron concentrate was mainly imported from Brazil and also provided by Jinshandian. The iron concentrates were dried and ground by the high pressure roller. The ground iron concentrates were pelleted by drum and disc pelletisers. The qualified green pellets were subjected to grate, rotary kiln, and ring cooler successively. The innovation and creation of process and equipment of the Ezhou pelletisation plant of Baowu plays an exemplary role for the application of large-scale grate-kiln-cooler in the iron and steel industry. The use of the high pressure roller grinding significantly improved the pelletisation ability of the iron concentrate and the quality of the finished pellets. Compared with other grinding equipment of the same scale, it is more energy efficient. The combined technique of high pressure roller with wet ball mill grinding was used to treat some hard specularite with large particle size. The first successful application and design of the electrostatic precipitator on the large-scale grate-kiln in China provides a good foundation for other large-scale pellet plants., The Ezhou pelletisation plant of Baowu, in China, with production capacity of 5 000 000 ton oxide pellets per year has the biggest single production line of grate-kiln ring cooler, provided by the Metso Company. The iron concentrate was mainly imported from Brazil and also provided by Jinshandian. The iron concentrates were dried and ground by the high pressure roller. The ground iron concentrates were pelleted by drum and disc pelletisers. The qualified green pellets were subjected to grate, rotary kiln, and ring cooler successively. The innovation and creation of process and equipment of the Ezhou pelletisation plant of Baowu plays an exemplary role for the application of large-scale grate-kiln-cooler in the iron and steel industry. The use of the high pressure roller grinding significantly improved the pelletisation ability of the iron concentrate and the quality of the finished pellets. Compared with other grinding equipment of the same scale, it is more energy efficient. The combined technique of high pressure roller with wet ball mill grinding was used to treat some hard specularite with large particle size. The first successful application and design of the electrostatic precipitator on the large-scale grate-kiln in China provides a good foundation for other large-scale pellet plants.

This work attempted to explore the feasibility of using iron-contaminated graphite concentrate as an effective adsorbent for Cr(VI) removal from polluted water. Adsorption isotherm and kinetics were conducted to investigate the Cr(VI) removal capacity by the iron-contaminated amorphous graphite concentrates. In addition, SEM-EDS, XPS were carried out to further examine the solid samples. The results showed that amorphous graphite concentrate had a 1.52 mg/g adsorption capacity of Cr(VI), with the adsorption being fitted well with the pseudo-second-order kinetics model. In addition, chemical adsorption of Cr(V) on iron-contaminated graphite concentrate due to the formation of Fe-O4HCr and Fe2-(CrO4)3 complexes was proposed. This study revealed that iron-contaminated amorphous graphite concentrate would be a cheap and good adsorbent for the removal of Cr(VI) from contaminated water. (Authors.), This work attempted to explore the feasibility of using iron-contaminated graphite concentrate as an effective adsorbent for Cr(VI) removal from polluted water. Adsorption isotherm and kinetics were conducted to investigate the Cr(VI) removal capacity by the iron-contaminated amorphous graphite concentrates. In addition, SEM-EDS, XPS were carried out to further examine the solid samples. The results showed that amorphous graphite concentrate had a 1.52 mg/g adsorption capacity of Cr(VI), with the adsorption being fitted well with the pseudo-second-order kinetics model. In addition, chemical adsorption of Cr(V) on iron-contaminated graphite concentrate due to the formation of Fe-O4HCr and Fe2-(CrO4)3 complexes was proposed. This study revealed that iron-contaminated amorphous graphite concentrate would be a cheap and good adsorbent for the removal of Cr(VI) from contaminated water. (Authors.)

Potential transformation of oolitic haematite into magnetite by mixing iron powder using the mechanochemical method has been achieved and discussed in this paper. The phase transition of pure haematite in the preliminary test was identified by X-ray diffractometer (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) techniques. The experimental results have shown that the crystallographic planes of magnetite, (220), (311), (400), and (511) were observed clearly in the Fe/a-Fe2O3 mixture after milling for 15 h, indicating that a-Fe2O3 had been effectively transformed into Fe3O4. The diffraction peaks of magnetite were also observed at d = 0.29605 nm (2theta = 30.163 degrees), 0.25226 nm (2theta = 35.559 degrees), 0.24156 nm (2theta = 37.190 degrees), and 0.20898 nm (2theta = 43.458 degrees) after 13 h milling-time. It suggests that the oolitic haematite is transformed into magnetite successfully by mechanochemical processing. The processing might be applied potentially for the magnetic separation of oolitic haematite. (Authors.), Potential transformation of oolitic haematite into magnetite by mixing iron powder using the mechanochemical method has been achieved and discussed in this paper. The phase transition of pure haematite in the preliminary test was identified by X-ray diffractometer (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) techniques. The experimental results have shown that the crystallographic planes of magnetite, (220), (311), (400), and (511) were observed clearly in the Fe/a-Fe2O3 mixture after milling for 15 h, indicating that a-Fe2O3 had been effectively transformed into Fe3O4. The diffraction peaks of magnetite were also observed at d = 0.29605 nm (2theta = 30.163 degrees), 0.25226 nm (2theta = 35.559 degrees), 0.24156 nm (2theta = 37.190 degrees), and 0.20898 nm (2theta = 43.458 degrees) after 13 h milling-time. It suggests that the oolitic haematite is transformed into magnetite successfully by mechanochemical processing. The processing might be applied potentially for the magnetic separation of oolitic haematite. (Authors.)

The depression effect of corn starch on the surface of muscovite mica powder at different pulp pH value was investigated. The flotation performance was studied by flotation tests, adsorption quantity measurement, zeta-potential technique and Fourier transform infrared (FT-IR). The results indicated that the depression effect was varied with the pulp pH value when dodecylamine chloride (DDA) was used as collector, the strongest inhibitory effect appeared at pH 2 and the zeta-potential of muscovite mica increased overall after conditioning with corn starch solution. It was confirmed by the FT-IR spectra that the corn starch indeed adsorbed on the surface of muscovite mica powder and physical adsorption occurred between muscovite mica and corn starch. This study leads to a better understanding of the depression effect of corn starch on the surface of muscovite mica powder., The depression effect of corn starch on the surface of muscovite mica powder at different pulp pH value was investigated. The flotation performance was studied by flotation tests, adsorption quantity measurement, zeta-potential technique and Fourier transform infrared (FT-IR). The results indicated that the depression effect was varied with the pulp pH value when dodecylamine chloride (DDA) was used as collector, the strongest inhibitory effect appeared at pH 2 and the zeta-potential of muscovite mica increased overall after conditioning with corn starch solution. It was confirmed by the FT-IR spectra that the corn starch indeed adsorbed on the surface of muscovite mica powder and physical adsorption occurred between muscovite mica and corn starch. This study leads to a better understanding of the depression effect of corn starch on the surface of muscovite mica powder.

Molybdenite particles exhibit two different types of surfaces, strongly hydrophilic surfaces resulting from the rupture the van der Waals force, termed ‘face’ and hydrophilic surfaces generated by the breakage of covalent Mo-S bonds, termed ‘edge’. Hydrophilic surfaces are produced when molybdenite crystals are broken along the edges, on which thiomolybdates can easily form as a result of oxidation and hydrolysis of molybdenum. The surface area of the edges can be greatly increased by reducing the particle size or with a decrease in the leading face/edge ratio. Theoretically the hydrophobicity of molybdenite depends on the face/edge ratio, and would exhibit weaker hydrophobicity at finer particle sizes. The contact angles of molybdenite powders in the size fractions (+150, -150 + 75, -53 + 38, -38 + 20, and -5 micrometres were determined using the Washburn method by measuring the mass of capillary rise liquids in molybdenite powder beds as a function of time. The results showed that molybdenite powders exhibited a smaller contact angle in the superfine size range of -5 micrometres than the common size range of +20 micrometres, which may be attributed to a large decrease in the face/edge ratio. The contact angles were very similar for the +150, -150 + 75, -53 + 38 and -38 + 20 micrometres fractions, indicating that they did not change with decreasing particle size for particles larger than +20 micrometres., Molybdenite particles exhibit two different types of surfaces, strongly hydrophilic surfaces resulting from the rupture the van der Waals force, termed ‘face’ and hydrophilic surfaces generated by the breakage of covalent Mo-S bonds, termed ‘edge’. Hydrophilic surfaces are produced when molybdenite crystals are broken along the edges, on which thiomolybdates can easily form as a result of oxidation and hydrolysis of molybdenum. The surface area of the edges can be greatly increased by reducing the particle size or with a decrease in the leading face/edge ratio. Theoretically the hydrophobicity of molybdenite depends on the face/edge ratio, and would exhibit weaker hydrophobicity at finer particle sizes. The contact angles of molybdenite powders in the size fractions (+150, -150 + 75, -53 + 38, -38 + 20, and -5 micrometres were determined using the Washburn method by measuring the mass of capillary rise liquids in molybdenite powder beds as a function of time. The results showed that molybdenite powders exhibited a smaller contact angle in the superfine size range of -5 micrometres than the common size range of +20 micrometres, which may be attributed to a large decrease in the face/edge ratio. The contact angles were very similar for the +150, -150 + 75, -53 + 38 and -38 + 20 micrometres fractions, indicating that they did not change with decreasing particle size for particles larger than +20 micrometres.

The preparation was investigated of porous haematite for use as an adsorbent for the treatment of wastewater containing heavy metals. The process involved the thermal decomposition of a goethite concentrate obtained from an iron ore concentration plant in Guangdong, China. The concentrate was calcined in a muffle furnace and the effects of temperature and residence tine were investigated. At a calcining temperature of 200 degrees C no decomposition occurred, but at 300 degrees C only haematite was identified and no composition changes were observed at higher temperatures. The haematite consisted mainly of micropores, which significantly increased the specific surface area and pore volume. The mechanism may involve the dehydration and dehydroxylation of goethite during the thermal treatment. At higher temperatures sintering of the haematite may occur, resulting in the merging of micro- and meso-pores and reducing the specific surface area. The mes-pores decreased with increasing residence time, but the average dimensions of the micropores and meso-pores exhibited no apparent changes., The preparation was investigated of porous haematite for use as an adsorbent for the treatment of wastewater containing heavy metals. The process involved the thermal decomposition of a goethite concentrate obtained from an iron ore concentration plant in Guangdong, China. The concentrate was calcined in a muffle furnace and the effects of temperature and residence tine were investigated. At a calcining temperature of 200 degrees C no decomposition occurred, but at 300 degrees C only haematite was identified and no composition changes were observed at higher temperatures. The haematite consisted mainly of micropores, which significantly increased the specific surface area and pore volume. The mechanism may involve the dehydration and dehydroxylation of goethite during the thermal treatment. At higher temperatures sintering of the haematite may occur, resulting in the merging of micro- and meso-pores and reducing the specific surface area. The mes-pores decreased with increasing residence time, but the average dimensions of the micropores and meso-pores exhibited no apparent changes.

The specific adsorption of hydrolysed Cr species on kaolinite surface was studied. Mexican kaolinite was purified first by using a high-intensity magnetic separator to remove Fe mineral particles and then by screening to remove coarse particles. The electrokinetic behaviour of kaolinite particles in aqueous sodium salt solutions (NaCl) in the presence of chromium chloride showed that kaolinite can reverse its charge. The zeta potential was negative in the range of pH 2-12 and no isoelectric point (IEP) appeared without CrCl3. The zeta potential increased as pH increased from 2.5 to approximately 6; it then decreased with pH and approached a value as though CrCl3 were not present. The adsorption of Cr on kaolinite reached a maximum value at a pH of approximately 6, which was the precipitation pH (ppt) of chromium hydroxide at the corresponding CrCl3 concentration and then kept a plateau to pH 6.3-6.5. This adsorption followed the Langmuir isotherm and was irreversible; and a chemical adsorption model between kaolinite surfaces and the hydrolysed multivalent metal species was proposed., The specific adsorption of hydrolysed Cr species on kaolinite surface was studied. Mexican kaolinite was purified first by using a high-intensity magnetic separator to remove Fe mineral particles and then by screening to remove coarse particles. The electrokinetic behaviour of kaolinite particles in aqueous sodium salt solutions (NaCl) in the presence of chromium chloride showed that kaolinite can reverse its charge. The zeta potential was negative in the range of pH 2-12 and no isoelectric point (IEP) appeared without CrCl3. The zeta potential increased as pH increased from 2.5 to approximately 6; it then decreased with pH and approached a value as though CrCl3 were not present. The adsorption of Cr on kaolinite reached a maximum value at a pH of approximately 6, which was the precipitation pH (ppt) of chromium hydroxide at the corresponding CrCl3 concentration and then kept a plateau to pH 6.3-6.5. This adsorption followed the Langmuir isotherm and was irreversible; and a chemical adsorption model between kaolinite surfaces and the hydrolysed multivalent metal species was proposed.

Microporous minerals have been widely used in industry as catalysts, cation exchangers, adsorbents and sequestering agents. Their most important use is in disposing of waste water, as in exchanging deleterious metal cations, removing radioactive substances and as auxiliaries in laundry detergent. Due to their good physical and chemical properties, they are also used for nanotechnology, functional materials and microelectronics. This review highlights the preparation of microporous minerals and in particular thermal treatment, including thermal modification and thermal synthesis, categorised into hydrothermal synthesis, solvothermal synthesis in which a solvent is substituted for the water in hydrothermal synthesis, microwave synthesis and dried gel method. Microwave irradiation as an advanced heating method for preparing microporous minerals is described. The mechanisms by which pores are formed in minerals through the thermal modification and synthesis processes are separately summarised. Other mechanisms highlighted are the liquid-crystal templating mechanism and cooperative formation mechanism. The important parameters affecting the thermal modification are heating temperature, thermal treatment time and rate of temperature increase whereas the parameters affecting thermal synthesis are the use of surfactant, including type, chain length and concentration, temperature, heating time and the concentration of the inorganic ions in synthesising solutions that synthesise the microporous minerals. Finally, various instrumental techniques are presented, in particular nitrogen physical adsorption to characterise microporous minerals., Microporous minerals have been widely used in industry as catalysts, cation exchangers, adsorbents and sequestering agents. Their most important use is in disposing of waste water, as in exchanging deleterious metal cations, removing radioactive substances and as auxiliaries in laundry detergent. Due to their good physical and chemical properties, they are also used for nanotechnology, functional materials and microelectronics. This review highlights the preparation of microporous minerals and in particular thermal treatment, including thermal modification and thermal synthesis, categorised into hydrothermal synthesis, solvothermal synthesis in which a solvent is substituted for the water in hydrothermal synthesis, microwave synthesis and dried gel method. Microwave irradiation as an advanced heating method for preparing microporous minerals is described. The mechanisms by which pores are formed in minerals through the thermal modification and synthesis processes are separately summarised. Other mechanisms highlighted are the liquid-crystal templating mechanism and cooperative formation mechanism. The important parameters affecting the thermal modification are heating temperature, thermal treatment time and rate of temperature increase whereas the parameters affecting thermal synthesis are the use of surfactant, including type, chain length and concentration, temperature, heating time and the concentration of the inorganic ions in synthesising solutions that synthesise the microporous minerals. Finally, various instrumental techniques are presented, in particular nitrogen physical adsorption to characterise microporous minerals.

Iron oxide minerals are good adsorbents for arsenic to eliminate it from contaminated water. This review highlights the use of goethite, haematite, siderite, limonite, ferrihydrite and magnetite, their adsorption capacities and the main factors in their removal of As, and discusses the mechanisms by which arsenic species adsorb on iron oxide minerals. The process is mainly attributed to chemical adsorption through the formation of binuclear bridging complexes Fe-O-AsO(OH)-O-FE on the minerals. Synthesised goethite showed the largest arsenic adsorption capacity., Iron oxide minerals are good adsorbents for arsenic to eliminate it from contaminated water. This review highlights the use of goethite, haematite, siderite, limonite, ferrihydrite and magnetite, their adsorption capacities and the main factors in their removal of As, and discusses the mechanisms by which arsenic species adsorb on iron oxide minerals. The process is mainly attributed to chemical adsorption through the formation of binuclear bridging complexes Fe-O-AsO(OH)-O-FE on the minerals. Synthesised goethite showed the largest arsenic adsorption capacity.

Of the two Mexican malachite samples studied, the Northcopper ore has thin films of malachite coating silicate and calcite gangue particles whereas in the Lupe ore the malachite particles are associated with gangue in the form of granules. Acid leaching experimental results showed a close correlation between morphology and leaching kinetics, the thin-film malachite having a much higher leaching rate and greater Cu recovery as a result of its larger phase-specific surface area and greater exposure by preferential breakage along the malachite-coated surfaces., Of the two Mexican malachite samples studied, the Northcopper ore has thin films of malachite coating silicate and calcite gangue particles whereas in the Lupe ore the malachite particles are associated with gangue in the form of granules. Acid leaching experimental results showed a close correlation between morphology and leaching kinetics, the thin-film malachite having a much higher leaching rate and greater Cu recovery as a result of its larger phase-specific surface area and greater exposure by preferential breakage along the malachite-coated surfaces.

Studies have been carried out of hydrophobic and magnetic combined flocculation using rhodochrosite and siderite. Combined flocculation was shown to be much stronger than hydrophobic or magnetic flocculation alone. Calculation of the potential energy of interaction between rhodochrosite particles in combined flocculation shows that although a magnetic field alone does not cause a strong flocculation it can markedly enhance the flocculation of hydrophobic particles in aqueous solution. The intensifying action of the magnetic field reduces or even eliminates the potential energy barrier of interaction between hydrophobic particles., Studies have been carried out of hydrophobic and magnetic combined flocculation using rhodochrosite and siderite. Combined flocculation was shown to be much stronger than hydrophobic or magnetic flocculation alone. Calculation of the potential energy of interaction between rhodochrosite particles in combined flocculation shows that although a magnetic field alone does not cause a strong flocculation it can markedly enhance the flocculation of hydrophobic particles in aqueous solution. The intensifying action of the magnetic field reduces or even eliminates the potential energy barrier of interaction between hydrophobic particles.

Theoretical and experimental study was made of the flocculation in an external magnetic field of fine paramagnetic particles rendered hydrophobic by adsorption of surfactants. The theoretical stability of the particles in aqueous suspension was proposed by extension of classical DLVO theory. The potential energies of interaction in an external magnetic field were then calculated for fine rhodochrosite particles with adsorbed sodium oleate. Experimental results for fine rhodochrosite and siderite particles showed that the combined process exhibits much stronger and faster aggregation than either hydrophobic or magnetic flocculation alone. An artificial mixture of fine rhodochrosite and quartz was well separated, with 7.8% higher concentrate grade and 6.3% higher concentrate recovery than for hydrophoobic flocculation alone. A recovery of 77% was achieved for refractory siderite ore from Da ye in Hubei, a 7% improvement on recovery from hydrophobic flocculation., Theoretical and experimental study was made of the flocculation in an external magnetic field of fine paramagnetic particles rendered hydrophobic by adsorption of surfactants. The theoretical stability of the particles in aqueous suspension was proposed by extension of classical DLVO theory. The potential energies of interaction in an external magnetic field were then calculated for fine rhodochrosite particles with adsorbed sodium oleate. Experimental results for fine rhodochrosite and siderite particles showed that the combined process exhibits much stronger and faster aggregation than either hydrophobic or magnetic flocculation alone. An artificial mixture of fine rhodochrosite and quartz was well separated, with 7.8% higher concentrate grade and 6.3% higher concentrate recovery than for hydrophoobic flocculation alone. A recovery of 77% was achieved for refractory siderite ore from Da ye in Hubei, a 7% improvement on recovery from hydrophobic flocculation.

Adding a collector or non-polar oil emulsion to an extremely fine mineral suspension can intensify the induction of hydrophobic flocculation of extremely fine mineral particles, forming floc. The floc size and structure have been studied. Experimental results show that the size is within the optimal size range of conventional mineral processing. The flotability is identical to that of particles of normal size. The floc has a compact structure which becomes more compact with an increase in non-polar oil., Adding a collector or non-polar oil emulsion to an extremely fine mineral suspension can intensify the induction of hydrophobic flocculation of extremely fine mineral particles, forming floc. The floc size and structure have been studied. Experimental results show that the size is within the optimal size range of conventional mineral processing. The flotability is identical to that of particles of normal size. The floc has a compact structure which becomes more compact with an increase in non-polar oil.

The action of a non-polar oil emulsion on the hydrophobic flocculation of fine mineral particles rendered hydrophobic by collector adsorption was studied. A mechanism and energy model for the interaction between the induced hydrophobic mineral particle and the non-polar oil droplet are proposed., The action of a non-polar oil emulsion on the hydrophobic flocculation of fine mineral particles rendered hydrophobic by collector adsorption was studied. A mechanism and energy model for the interaction between the induced hydrophobic mineral particle and the non-polar oil droplet are proposed.

The investigation shows that hexametaphosphate has two effects: repulsion resulting from the steric effect and static-electric repulsion resulting from negative charges. The former is a primary factor. Both of them function jointly resulting in the dispersed state of extremely fine rhodochrosite in suspension., The investigation shows that hexametaphosphate has two effects: repulsion resulting from the steric effect and static-electric repulsion resulting from negative charges. The former is a primary factor. Both of them function jointly resulting in the dispersed state of extremely fine rhodochrosite in suspension.