Fundamental Studies on Interfacial Tensions in Flotation. I : Determination of Surface Tension with Data on Aqueous Solutions of Frothers

(1) The determination of surface tension by the ring method is studied in detail. (2) A metal fitting for indicating the normal position of the beam of the tensiometer is devised and the scale is calibrated. (3) The measuring dish and the circulating pump, made of glass and capable of agitating and feeding fresh liquid at any constant temperature, are developed. The constant-temperature water bath for the circulating pump is described. (4) The error due to the rise of the beam from the zero point during measurement of the surface tension of pure water prepared by distillation from alkaline permanganate and from sulphuric acid amounts to 4.5°in angle or 0.033 g in weight. (5) It is shown that the accurate value of the surface tension of pure water of 71.82 dynes/cm at 26.2℃, differing by only 0.03 dyne/cm from the standard value given in the International Critical Tables, can be obtained by the Du Nouey\u27s tensiometer modified by the author with adequate precautions. (6) The syringe fused with a glass capillary is used for the preparation of aqueous solutions of frothers and it is accurately weighed by inserting it in a glass cap. The error of the ordinary method using the average weight of 10 or more drops as the weight of one drop of frother, is found to be about 1% in summer and 2% in winter for terpineol. (7) Various existing equations expressing the relation between the surface tension and concentration of solutions are critically studied. (8) The measured values of the surface tension of aqueous solutions of pure as well as commercial frothers are in good agreement with the values calculated by Szyszkovski\u27s equation

Fundamental Studies on Interfacial Tensions in Flotation. IV : Suspended-Plate Method of Determining Wetting Tension and the Time Variation of Wetting Tension of Glass at Water-Air Interface

A new method of measuring wetting tension of solids with a suspended plate was developed. The method enables us the precise as well as rapid measurement of the wetting tension. In order to contribute to the study of the wettability of pure surface of minerals, the wettability of a glass plate, which was selected as an example because of its perfect wettability and ease of cleaning, was measured. The method of cleaning in which glass was immersed in an ethyl alcohol solution of sodium hydroxide and then washed with distilled water, was found to be simple and yet very effective. The wetting tension of crystal glass against pure water was measured to be 71.97 dynes/cm at 24.9℃, that is the contact angle was zero. The larger values of contact angle of glass given in literatures were discussed and the causes were summarized. The time variation of the wetting tension of a clean glass plate was measured precisely. It was assumed that the change of the wettability of clean glass surfaces on standing was due to the adsorption of air or vapour from the atmosphere. From the theoretical consideration of simple adsorption of gas on the surface of solids, the wetting tension-time equation was derived. It was verified that the equation held good. From the equation the characteristic values as the wetting tension at zero time, that at infinite time, the wetting velocity, that at zero time and the time required for the wetting tension to go half way to its final value was obtained. These values may be utilized for the investigation of wetting characteristics of solids

Five-Wheeled Wheelchair with an Add-On Mechanism and Its Semiautomatic Step-Climbing and -Descending Function

In this chapter, we propose a novel add-on electric drive system for propelling a manual wheelchair on the floor together with an advanced function to climb and descend a step with no human support. The proposed add-on mechanism consists of an active-caster drive wheel and a reconfigurable link mechanism with a linear actuator to change the location of the drive wheel relative to a wheelchair. By attaching the mechanism to a manual wheelchair, we build a five-wheeled wheelchair. Since the drive wheel is attached on the back of the wheelchair, a risk of falling to the back is significantly reduced. To surmount a step with no help, we develop a step-climbing and -descending strategy by using the proposed wheelchair with a reconfigurable link mechanism. The five-wheel configuration guarantees a static stability of the wheelchair when some wheels are hovered from the ground. The function is used in step-climbing and -descending strategies to realize the transfer of a wheelchair user. In order to reduce the effort of a wheelchair user to control the complicated step surmount strategies, semiautomatic system is installed on the prototype wheelchair whose availability is verified through experiments

Fundamental Studies on Interfacial Tensions in Flotations. III : Tilting-Plate Method of Determining Contact Angle and the Wetting Tension of Aqueous Solutions of Frothers for Paraffin-Wax

For the study of the theory of flotation process as well as the flotation agents, the wettablility of paraffin-wax in aqueous solutions of pure frothers as iso-amyl alcohol, meta-cresol, a-terpineol, d-camphor and of a few commercial frothers were measured. By considering critically the reciprocal action of interfacial energies among solid, liquid and gas, the product of the surface tension of the liquid and the cosine of the angle of contact was selected as the wettability of solid against liquid. For the measurement of angle of contact, the tilting-plate method was selected and the modified form of the apparatus was developed, in which all parts in contact with liquid under test were made of glass only and the advancing and receding angles were measured more or less readily and precisely by agitating, circulating, and regulating the liquid at any temperature. For the surface tension of solutions, the values obtained by Du Nouy\u27s tensiometer were utilized. A new wetting isotherm was derived, which held good for the wetting of paraffin-wax in solutions of pure as well as commercial frothers. The wetting isotherm was entirely similar in form to Szyszkovski\u27s equation for water-air interface. By analogy, the wetting activity and the orientation of frothers at paraffin-water interface were considered and it was shown that wetting activity and the orientation of frothers at paraffin-water interface was similar to those at water-air interface

Fundamental Studies on Interfacial Tensions in Flotation. II : Surface-Tension Variation, Surface Activity, and Surface Orientation of Frothers at Air-water Interface

It has been found that the surface tension of cineol solutions varies appreciably with time during measurement by a tensiometer. This fact will have considerable influence on froth characteristics in flotation. Therefore time variation of surface tension of aqueous solutions of frothers has been theoretically considered and two equations are introduced according to the assumption whether or not the rate of diffusion of molecules to the surface from the body of a solution is small as compared with that of evaporation. It is verified experimentally that the equation obtained on the former assumption holds good in the aqueous solutions of cineol. The time variation of the concentration of a solution may also be obtained by the surface tension measurement using this equation. The activity coefficients of pure as well as commercial frothers are calculated. An equation for the relation between surface pressure and the surface concentration of various frothers is introduced and it is concluded that the difference in the surface activity of frothers are mainly due to the ease of adsorption of the molecules of frothers to the surface from the body of a solution. The relation between the surface pressure and the area occupied by a gram molecule is expressed by a formula, which coincides with that of Schofield and Rideal for higher surface pressure. The least area that a molecule can occupy and the reciprocal of the molecular cohesion in Schofield and Rideal\u27s equation are calculated for each frother

Recovery of Ferreous and Other Minerals in Laterites

Laterites are found in the tropics deposits as the residual soils and consists largely of aluminium and ferric hydroxides, with more or less free silica and other constituents, varying widely in composition and purity. The process of beneficiation may be defined as concentration or preparation for smelting iron ores that is facilitated by separating mineral aggregates into homogeneous materials. Hence, the heterogeneity of constituent minerals in laterites is the prerequisite of beneficiating laterites. The present paper deals with the experiments of beneficiating a lateritic ore from Phillipines. The constituent minerals such as goethite, hematite, maghemite, magnetite, ilmenite, chromite and pyrite have been identified under the microscope. The close examination of the characteristics of these minerals led us to develop a new process of beneficiating laterites, called "Roast-High Intensity-Thermomagnetic Separation." The description is given of the flowsheet for the treatment of laterites by means of the "R-H-T process." The results of separation are discussed in terms of chemical analyses, X-ray diffraction and electron-probe microanalyses

A Research on the Treatment of Complex Sulphide Ores. IV : Selective Flotation of Sulphatization Residue

In this report, the recoveries with selective flotation of chalcopyrite, pyrite and lead sulphate from the sulphatization residue of the bulk sulphide concentrate from the Hanaoka mine were dealt with. The advantage of the process combining flotation with sulphatization, from the standpoint of flotation, may be considered to be as follows : (a) The liberation of minerals will be promoted chemically, (b) the surface of mineral grains will be cleaned, and (c) the separation of minerals in the residue will be easier than that in the original ore. The samples of sulphatization residue containing 4.3 to 5.7% Cu, 14.5 to 20.0% Fe, 6.2 to 13.9% Pb, and 2.3 to 3.2% Zn, and of -150-mesh size, were subjected to tests. The main problems in the selective flotation were the floatability of lead sulphate produced by sulphatization and the degree of regrinding necessary for the liberation of chalcopyrite from pyrite. It was verified experimentally that the chemically pure lead sulphate was depressed at the pH of below 5.8 or above 6.2 when Aerofloat No. 25 was used as a collector and was floated at the pH of 8 to 9 when it was sulphidized with the predetermined quantity of sodium sulphide and potassium amyl xanthate was used as a collector. The sulphatization temperature suitable for the separation of chalcopyrite and pyrite from lead sulphate from the standpoint of flotation was found to be 160゜ to 170℃ in the temperature range of 1.30° to 170℃. In the separation of chalcopyrite and pyrite from lead sulphate, the recoveries were 92.9% for Cu and 96.2% for Fe and the rejection was 83.5% for Pb with 0.1 kg/t of white camphor oil and 0.13 kg/t of Aerofloat No. 25 and at the pH of 6. In the recovery of lead sulphate, the lead concentrate containing 36.7% Pb was obtained with the Pb recovery of 89.8% with 30 kg/t of sodium sulphide, 0.6 kg/t of white camphor oil and 1.0 kg/t of potassium amyl xanthate and at the pH of 9.2. In the separation of chalcopyrite from pyrite, three stages of regrinding, one stage of roughing and two stages of scavenging were required to obtain the copper concentrate of 9.9% Cu with the Cu recovery of 95.2% and the pyrite concentrate of 41.4% Fe with the Fe recovery of 61.4% with 0.7 kg/t of white camphor oil, 0.8 kg/t of Aerofloat No. 25 and 60 kg/t of slaked lime and at the pH of 10, 6. The size of the flotation products was very minute when microscopically examined, namely, the bulk of -20 micron material was 72.5% for the copper concentrate, 74.8% for the lead concentrate, 40.2% for the pyrite concentrate, and 16.7% for the tailing. The highest grade of concentrates obtained was relatively low, namely, 49.2% Pb for the lead concentrate, 11.7% Cu for the copper concentrate, and 41.4% Fe for the pyrite concentrate. It was, however, considered that a higher grade could not be obtained, because the degree of grinding of the sample was near the limit in flotation. The overall recoveries in the selective sulphatization and flotation were 97% for zinc, 90% for copper, 77% for lead, and 58% for iron

Studies on the Flotation of Molybdenite. I : Flotation of Molybdenite Ore Containing Clayey Gangue

Some points to be considered in the flotation of molybdenite containing clayey gangue were investigated, and based on the results obtained, the method of flotation operation was examined at the Daito mine, Shimane Prefecture. In the rougher flotation of molybdenite ore, high concentrate grade and recovery can be obtained by selecting the proper ratio of silica to soda and suitable concentration of sodium silicate to be added. Sodium silicate having the ratio of silica to soda 2 : 1 shows the most effective depressing action on gangue minerals. The minimum content of SiO_2 in the froth product is obtained when the conditioning time after adding sodium silicate is 10-20 minutes. It is preferable to use sodium hydroxide instead of lime to regulate the pH value of the pulp containing much primary slime. On the contraty, lime is effective for the flotation of molybdenite ore containing no primary slime. Though it is usual to use oily collectors as collecting agents for molybdenite, quantities to be added to obtain good flotation results are unexpectedly large. In some cases molybdenite can be recovered at high rates of recovery by using xanthate with oily collector, but we should be cautious of using much xanthate. However, a good flotation result cannot be expected with xanthate only. At the Daito mine, the flotation results have been improved by modifications of flotation methods : slime is treated by a separate flotation circuit and the froths are returned to the main circuit. Sodium hydroxide is used to regulate the pH value of the pulp. Thus, no difficulty has been experienced in producing a molybdenite concentrate assaying 86.3-87.4% MoS_2 with a recovery of 95.5-97.9% from a flotation feed assaying 1.06-1.13% MoS_2