Study on the pH Dependence for Copper Activation of Sphalerite

The pH dependence of copper activation on sphalerite was studied by measuring the adsorption of copper ions as a function of pH. The adsorption of copper ions was maximum at about pH 5～6 and decreased rapidly in both the acid and akaine region. From the results obtained, it was recognized that the pH dependence for the adsorption of copper ions on sphalerite was remarkable. The cause for the decrease of the copper adsorption on sphalerite in the alkaline region was investigated. The dependence of concentration of copper ions in the solution for the copper adsorption on sphalerite was examined. From the results, it was recognized that the copper adsorption on sphalerite decreased with a lowering of the concentration of copper ions in the solution. Then, the kinetics for the adsorption of copper ions on sphalerite was investigated. The reaction rate of the copper adsorption on sphalerite was shown by the reaction equation of the 1st order, and the relationship between the adsorption rate of copper ions on sphalerite and the agitation rate was characterized by a straight line in the log-log plot. The above results suggested that the decrease of the copper adsorption on sphalerite in the alkaline region might be due to the decrease of the copper concentration in the solution with the increase of the pH value, and consequently to the decrease of the diffusion rate at which the copper ions diffused to the surface of sphalerite from the bulk in the solution. The cause for the decrease of the copper ions in the acid region was analysed experimentally. With regard to the results, it was surmised that the formation of copper sulphide led to the decrease of the copper concentration in the solution. The formation of copper sulphide was caused by the generation of H₂S resulting in the dissolution of sphalerite in the acid solution. Accordingly, there was a decrease of the copper concentration in the solution and of the diffusion rate of copper ions. As mentioned above, the reaction rate of the copper adsorption on sphalerite was determined by the diffusion rate of copper ions

Copper Ion Adsorption on Sphalerites of Various Iron Contents

The kinetics for copper ion adsorption on sphalerites of various iron contents were studied by measuring the adsorption of copper ions in the presence of oxygen and in oxygen free circumstances. The relationship between the copper ion adsorption rate and the agitation rate was characterized by a straight line in the log-log plot. With the increase of iron contents in the sphalerite, the copper ion adsorption rate on the sphalerite decreased in the case where oxygen was sufficiently dissolved in the copper ion solution and the pH was high enough. The reaction rate of the copper ion adsorption on sphalerites changed from the rate of a parabolic function to the rate of an exponential function with the increase of iron contents in the sphalerite. As a result, in the above stated conditions, it was surmised that the kinetics for the copper ion adsorption on sphalerites of various iron contents were considerably complex. The kinetics for copper ion adsorption on pyrrhotite were explained by the protective film theory. From the above results, it may be considered that the dissolved oxygen in the pulp is one of the important factors for the copper activation on sphalerites

Study on Deactivation of Sphalerite with Sulphuric Acid and Ferric Ion Solutions

The separation of Cu/Zn ores in the flotation treatment of complex sulphide ores is very difficult because of copper activation. Therefore, the deactivation of copper-activated sphalerite is one of the most important subjects in the flotation operation of complex sulphide ores. In this study, the deactivation of copper-activated sphalerite has been investigated in a series of laboratory experiments. Firstly, the effects of sulphuric acid and ferric ions in the presence of sulphuric acid on the deactivation of copper-activated sphalerite were examined from the flotation tests by the Hallimond tube. From the results obtained, it was found that the deactivation of copper-activated sphalerite could be attained to some degree by a 3～5 vol. % H₂SO₄ solution, and could be attained very well by a 500～l, 000 mg/1 Fe⁺⁺⁺ solution containing H₂SO₄. In this case, oxygen gas accelerated the deactivation of the sphalerite in the treatment of both the above solutions. Temperature was also one of the important factors for the deactivation. Secondly, the dissolution of the copper-activated film formed on the sphalerite was investigated. From the results obtained, it was found that copper-activated film could be dissolved completely by the Fe⁺⁺⁺ solution containing H₂SO₄, and could be dissolved to some degree by the H₂SO₄ solution. The dissolution rate of the activated film was measured as a function of the concentration of Fe⁺⁺⁺ and H₂SO₄ and of the temperature. The dissolution rate is shown by a linear equation. Using a flotation machine, a series of differential flotation tests of Cu/Zn sulphide ores was carried out. From the results obtained, it was confirmed that the flotation separation of Cu/Zn sulphide ores was successful by the deactivation treatment for the Cu/Zn sulphide ores

Effect of Sodium Sulphide on the Prevention of Copper Activation for Sphalerite

The effect of sodium sulphide on the prevention of copper activation for sphalerite was studied. The adsorption of copper ions on sphalerite was measured in a solution containing copper ions and sodium sulphide by varying the pH value of the solution. From the results obtained, it was recognized that the adsorption of copper ions was prevented completely in an alkaline solution containing sodium sulphide. When sodium cyanide was used as a depressant, the effect of sodium sulphide on the prevention of copper activation was investigated. Up to a certain amount of sodium cyanide, the floatability of sphalerite increases with the increase of sodium cyanide. It was confirmed that this phenomenon was caused by coating copper sulphide particles or copper complexes precipitated by sodium sulphide on the sphalerite surface. However, by increasing the concentration of sodium cyanide to over 30 mg/1 and by the addition of sodium sulphide, it was seen that the depressing effect of sodium cyanide was considerable. In the case where sulphurous acid was used as a depressant, the floatability of sphalerite did not decrease at the low pH value, and colloidal sulphur was formed by the decomposition of sodium sulphide. However, with the increase of the pH value and the amounts of sulphurous acid, the depressing effect of sulphurous acid in the presence of sodium sulphide was most marked. Consequently, it may be considered that copper activation for sphalerite is prevented completely when using sodium sulphide

Study on the Removal of Inorganic and Organic Mercury in Waste Water by the Flotation Method

The removal of inorganic and organic mercury in waste water by the flotation method was investigated as a part of the intensive studies of the water pollution control. The removal of inorganic mercury was examined by the following two methods : 1) Fe(OH)₃ co-precipitation-flotation method, 2) Fe(OH)₃ co-precipitation-Na₂S precipitation-flotation method. From the results obtained, it was recognized that inorganic mercury in waste water could be efficiently removed by the Fe(OH)₃ co-precipitation-flotation method with 80 mg/l cumulative addition of ferric ions in the pH about 9 after the third stage flotation using sodium oleate as a collector. By the first stage flotation, however, the removal of inorganic mercury in the waste water was inefficient. So, sodium sulphide was added to the waste water in order to precipitate completely the mercury. Thus, the precipitates of inorganic mercury produced with 40 mg/l ferric ions and 1 equivalent addition of sodium sulphide to the total amounts of mercury were completely removed at the pH 6.5―9.5 using sodium oleate in only the first stage flotation. The removal of organic mercury in waste water was performed by the following methods. A substance which contains organic mercury was decomposed into inorganic mercury with gaseous chlorine, followed by the Fe(OH)₃ co-precipitation-flotation method and the Fe(OH)₃ co-precipitation-Na₂S precipitation-flotation method. The decomposition of organic mercury into inorganic mercury was achieved readily by the oxidation reaction using Cl₂ gas. The optimum conditions of this reaction were found at pH below 1. The removal of excess chlorine in the flotation pulp is important for a successful flotation of the precipitates. The excess chlorine was eliminated by 8 g/l sodium thiosulphate or the aeration over 40 min. It was found that the mercury decomposed by Cl₂ gas was completely removed by the flotation method with an addition of 50―100 mg/l ferric ions and 1 equivalent of sodium sulphide to the total amounts of mercury at the pH 5.0―9.5. This new method being applied, the removal of inorganic and organic mercury in the waste water was successful in a short time by only one stage flotation using sodium oleate, and mercury in the tailing solution was not detected

Effect of Grinding Aids upon Ball Milling of Cement Clinker

The effect of varying concentrations of ε-caprolactam, stearamide, acrylamide, triethanolamine and diethylene glycol upon the grinding of a cement clinker in a laboratory mill was investigated. The beneficial effect of ε-caprolactam, so far apparently an unreported additive in clinker grinding, has been realized and comparatively studied against triethanolamine and diethylene glycol which have long been successfully used in the cement industry. The characteristics of the ground products have been ascertained by nitrogen adsorption, permeability, micro-mesh dry sieving and centrifugal sedimentation techniques. Among these, nitrogen adsorption has best characterized the comminuted materials

Recovery of Fine Monazite Particles by Liquid-Liquid Extraction

As a fundamental study with regards to the recovery of fine mineral particles by liquid-liquid extraction, the effect of sodium dodecylbenzenesulfonate (SDBS) as a surfactant has been investigated in terms of pH, SDBS concentration, zeta potential, contact angles, interfacial tensions and work of adhesion. Maximum recoveries were obtained at pH around 7 and SDBS concentration of 1 × 10⁻⁴ mol･dm⁻³. In alkaline solutions, the recovery of monazite decreased regardless of the SDBS concentration as the pH was increased above 7. An increase in the SDBS concentration up to 1 × 10⁻⁴ mol･dm⁻³ resulted in an increase in the recovery. It was considered that in the pH range below 7, an increase in the SDBS concentration brought about a higher coulombic adsorption density of the surfactant ions on the monazite particles which were charged positively, and resulted in higher recoveries. So as to examine a relationship between the oil-wettability and the recovery, contact angles and interfacial tensions were also measured in terms of pH and SDBS concentration. Based on the results obtained above, the work of adhesion was calculated. It was found that the work of adhesion was considerably related to the monazite recovery of the liquid-liquid extraction

Applicability of Precipitation-Flotation Method for Differential Separation of Cadmium from Zinc in Synthesized Waste Cyanide Water

The removal of heavy metal from synthesized waste cyanide water is achievable by a precipitation-flotation method. However, the differential separation of constituting metals by this method has been thought to be very difficult. The authors found that the addition of some decomposing reagents to the synthesized waste cyanide water of cadmium and zinc can improve the separation characteristics of these metals. The present study deals with the applicability of the precipitation-flotation method for the differential separation of cadmium from zinc in synthesized waste cyanide water. The proposed method was to use sodium sulphide as a decomposing reagent in the first stage of flotation and hydrogen peroxide in the second stage in order to decompose the Cd-CN and Zn-CN complexes, respectively. Furthermore, the use of such a cation flocculant as FC-80 was considerably effective for the removal of the Cd-CN complex. Based on a series of fundamental flotation tests, actual differential flotation tests were made. The separation of cadmium from zinc in synthesized waste cyanide water was found to be satisfactory. This method can be effective for the differential separation of difficult-to-sepa-rate colloidal precipitates from liquids by the sedimentation method

A Study on the Separation of Cadmium from Zinc in Synthesized Waste Cyanide Water by Precipitation Method

The present study deals with the applicability of a precipitation method for the differential separation of Cd-CN and Zn-CN complexes in synthesized waste water. In order to separate cadmium from zinc in synthesized waste cyanide water by the precipitation method, it was necessary to decompose the metal cyanide complexes prior to the precipitation treatment. From a series of tests, it was found that the pretreatment by the addition of sodium sulphide was effective for the selective precipitation of the Cd-CN complexes. On the other hand, the Zn-CN complexes were decomposed by the pretreatment of hydrogen peroxide, and then the zinc and cyanide ions were simultaneously precipitated by this method. This method being applied, it was found that the differential separation of the constituting metals was effectively achieved by this method

Recovery of Fine Ilmenite Particles from Beach Sand by Liquid-Liquid Extraction

In this fundamental study on the recovery of fine mineral particles by liquid-liquid extraction, the concentration of fine ilmenite particles at the iso-octane/water interface has been investigated using surfactants under different pH. Sodium oleate, sodium laurylbenzenesulfonate and stearylammonium acetate were used as surfactants to control the wettability of ilmente particles and to stabilize the iso-octane/water emulsion system in the extraction process. It was found that one hundred percent recovery of the ilmenite was obtained with the optimum pH and surfactant addition regardless of the surfactant used in this study. The distribution of neutral oleate and amine molecules between the aqueous and organic phases was examined by colorimetry. A good correlation was observed between ilmenite recovery and the concentration distribution of surfactant species