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By George Wilson

When pumping abrasive slurry mixtures, special attention must be given to pump design and construction. The second article in this two-part series describes some design features to consider when selecting centrifugal slurry pumps. Hydraulic Design Most centrifugal pumps are conventionally designed to achieve the desired hydraulic performance at the highest efficiency and lowest cost when handling clear fluids in reasonably clean environments. Manufacturing limitations are not imposed on the configuration of the pump, since conventional materials such as cast iron, bronze, and stainless steel are used. Manufacturers and buyers usually select the highest specific speed commensurate with the lowest cost attainable. Part life is almost infinite. When a centrifugal pump is designed for slurry service, the important factors in pump design are wear and materials of construction; size and efficiency assume lesser importance. The pump must operate at low rotational speed and the impeller has to be a truly radial flow design. These factors immediately determine that the pump must be of a low specific speed design in the range of 600 to 1800. The specific speed is a type number that is constant for all geometrically similar pumps; it designates the geometry of the impeller and casing. [ ] where n = rpm, Q = flow (US gpm), H = total head (ft), and Ns = specific speed. Since wear is a function of velocity it can be shown that for a given head and capacity, wear will increase with increased Ns. Centrifugal Pump Casing The casing has a profound effect on performance. If designed incorrectly it can destroy a large part of the energy given to the flow by the impeller, resulting in low efficiency, high hydraulic forces, and excessive wear on both the casing and impeller. In a conventional spiral volute, the static pressure around the impeller is uniform only when there is a free vortex velocity distribution in the volute, i.e., when the spiral flow from the impeller coincides with that of the volute spiral. This occurs only at the best efficiency point (BEP), between the pump's best operating zone and over capacity zone. Departure from the free vortex velocity distribution in the volute at partial or over capacities produces circumferential pressure gradients at the impeller periphery, which is directly proportional to the specific gravity of the mixture being pumped. At partial or over capacities, the flow will not tolerate the abrupt deflection at the tongue and severe energy losses and wear are created near the casing throat and on the impeller. Concentric and semi-concentric volute designs produce uniform static pressures at the impeller periphery and make the pump, much less sensitive to "off"' BEP operation. Hydraulic forces and wear are considerably reduced-eliminating the tongue prevents abrupt deflection of the flow, turbulence is minimized, and the velocity in the casing volute and throat is reduced. Good efficiency is sustained over a wider operating hand. Casings of this design are easy to cast. • Spiral volute (conventional)-Radius to the outer periphery of the casing and the volute area constantly increases. • Semi-concentric casing-Radius to the outer periphery of the casing and volute area remain constant within a certain angle. • Concentric casing-Radius to the outer periphery of the casing and volute area remain constant through 360°. The degree of concentricity must be reconciled with efficiency, hydraulic radial load, and wear for each specific speed chosen. Up to 1200 Ns the casings can be fully concentric without sacrificing too much efficiency. Above 1200 Ns, the casings can be semi-concentric. The angle of concentricity

Jan 10, 1981

By I Gipps

A vision of what the future mine involves all aspects of mining, ie orebody access, ore stoping, material transport, processing and waste material disposal. This paper examines one aspect of the future mine: rock extraction, stoping, automated for remote operation, high productivity and low cost. Concepts for the future require a re-think of the mining process and ROES® re-examines how bulk stoping of ore can be undertaken and how this should be redesigned to accommodate the possibilities that exists with remote control and automated operations.ROES® is a new mining system for underground mines and quarries utilising a shaft located close to or within the stope for the ore breakage process. The system is designed to exclude personnel from contact with production drilling, explosive placement and detonation so all of these tasks are remotely controlled or automated. Survey of the shaft, stope back and broken rock within the stope will occur, following each blast, by remote control or automated techniques. The survey will include excavation geometry, rock fragmentation, geotechnical characterisation and estimation of ore grade. Blastholes will be surveyed before placement of explosives and, with the survey data, the optimal explosive placement and blast timing will be determined with the best available information.ROES® is designed for application in open stoping or sublevel caving in disseminated, geologically defined, thick tabular or narrow vein ore bodies. Technologies developed for ROES® will also have potential applications to caving operations, reducing the risk of frozen ore and poor fragmentation. In a typical sublevel open stope application, ROES® will reduce the stope associated development by half and will allow ore to be brought on-stream sooner and at lower cost. Other savings will flow with the centralisation of mining activities and operational data, reduction in mining fleet, reduction in ventilation requirements, improved occupational safety and reduced mine complexity.

Nov 22, 2011

By C. H. Bloomster

This study estimated (1) radon and radon daughter emissions from underground uranium mines; (2) the reduction in radon that would be released to the surface by using control techniques such as bulkheads, sealants, backfilling, and positive pressure ventilation; (3) the cost for radon and radon daughter removal from total exhaust air; and (4) total radon and radon daughter discharge for lower occupational exposure limits. For 13 large underground uranium mines, estimated yearly radon emissions from each mine ranged from 900 to 3,400 Ci. The estimated age of air emitted from the mines ranged from 11 to 37 min. Potential radon removal methods for the total mine exhaust were evaluated. The cost of these methods was prohibitive. Diurnal and seasonal changes may affect radon emission over short periods of time, but do not affect the total emissions over the long run. Radon and radon daughter emissions would be little changed by increased ventilation requirements needed to achieve lower occupational exposure limits. The concentrations in the exhaust would be lower, but the total release would be the same

Jan 1, 1984

By Thomas A. Bailey

Since the advent of longwall mining, various methods and materials have been used during relocation to control the intrusion of the gob in the shield/panline area. (figure 1) Controlling this gob is critical to ensuring a safe, speedy, and productive longwall move. An uncontrolled gob can cause a number of problems, from increased worker exposure to entrapment of equipment to lost production. With an eye toward worker safety and increased productivity, several different methods have been developed to minimize gob intrusion. This presentation will take a look at the history and development of longwall ?screens? and ?mesh?, from chain-link fencing to high-modulus polyester geogrids. The benefits and advantages of these developments will be defined. Since 1994, longwall coal mines have used polymer geogrids during longwall recovery to control intrusion of gob material into the shield/pan line area. As described by Brandon and Collins (1996) in their paper presented at the 15th Ground Control Conference in Golden, CO., mines had used various forms of support, such as welded wire mesh, chain-link fencing, wooden cribbing, props, and steel cable to accomplish this. These methods worked, but were labor-intensive, slow, and provided varying degrees of gob stoppage. Although a few mines still use chain-ink fencing to control the gob, longwall coal mines have generally settled on polyester geogrids to control gob and roof and these mines have been instrumental in providing input in order to develop and improve these geogrids products. he trend during the past twelve years has been to incorporate stronger grids and to eliminate auxiliary reinforcements, such as steel cables and nylon or polyester webbing. A job that once required heavy steel cables, props, and fencing is now accomplished with strong, lightweight, high-modulus polyester grids. When we discuss high-modulus grids, we refer to the ratio between load and strain, as illustrated in figure 2. These grids are woven or knitted from yarns that have been pre-stressed. When these grids come under load, they pick up the load more quickly. This allows less deformation in, in this case, the mine roof. The same principle applies when these grids are used to control the ribs. With less elongation, the grids will hold rib material tighter, thereby keeping travel ways more open.

Jan 1, 2006

By K. Lundholm, M. Andersson, L. Nevatalo, Å. Holmström, L. Hedström

"Several copper deposits have the arsenic bearing minerals enargite (Cu3AsS4) and tennantite (Cu12As4S12). Since this mineral contain both arsenic and copper, it is not possible to remove the arsenic by selective flotation. Partial roasting is a method to clean the concentrate from arsenic and thereby produce a suitable raw material for the copper smelter. Also mercury is commonly found in copper bearing minerals. In the partial roasting process both arsenic and mercury are volatilized, while part of the sulphur is used as energy during the roasting. This gives a calcine suitable as feed to a smelter, much like an ordinary copper concentrate. A typical analysis of calcine would be: S content 18–22%, As content below 0.3%, Cu content – not affected, grain size – not affected. However, if the concentrate contains mercury, the mercury will be volatilized during the roasting process. This will lead to very high mercury contents in the subsequent process of sulphuric acid, unless the SO2-rich process gas is pre-treated by the Boliden/Norzink process that recovers mercury as calomel, Hg2Cl2. The volatilized arsenic in the gas phase can be recovered either by dry or wet methods. However, one problem is that arsenic also contaminates the fine grained calcine dust that is captured downstream in the gas cleaning system. The calcine dust contains valuable metals such as copper, gold and silver that needs to be separated from the arsenic. The ultimate aim is to stabilize the recovered arsenic as a compound with minimum impact on the environment and recover the valuable metals. By using wet recovery methods it is possible to selectively precipitate copper, gold and silver as sulphides while arsenic is kept dissolved in the liquid. The precipitated metal sulphides can be mixed with the calcine and sent to the copper smelter. The dissolved arsenic is sent to effluent treatment and is further treated in Outotec ferric arsenate precipitation process, where arsenic is precipitated as the stable compound basic ferric arsenate, formula FeAsO4·xFe(OH)3. All concentrates containing arsenic are unique and the process design of a roaster plant must be based on relevant process data. The process data is collected during tests in lab scale and pilot scale, where the influence of critical process parameters on the quality of calcine is studied. The ability to run tests both in lab scale and pilot scale is crucial to the development of the correct roasting process. Outotec is well equipped for this."

Jan 1, 2014

By Vic Sterner

As cities and towns continue to grow, the need to install sewer, water, gas and other utilities becomes a necessity and the blasting of trenches for these service lines probably constitutes one of the most important forms of blasting in built-up areas. There f o re, understanding how explosives can be safely used in the most efficient manner is of prime importance. The need for protection against flyrock must be emphasized. The first consideration is that all explosive c h a rges should be located well down in the blastholes. The golden rule is to ensure that the depth of top stemming is never less than the burden on the hole. In the case of shallow holes, the minimum depth of stemming should not be less than 18 times the charge diameter, if airblast and flyrock are to be controlled. If there is a doubt, then additional cover and/or blasting mats should be used. Putting too much burden on blastholes is another possible cause of flyrock and raising ground vibration levels. Overburdening of explosive charges will also result in the blastholes not breaking to grade. This in t u rn re q u i res additional drilling of shallow holes down in the trench to achieve grade, thus further increasing the h a z a rd of flyrock .

Jan 1, 2004

By Mani Manimaran, Inna Dymov, Mariam Melashvili, Chris Fleming, Joe O’Day

This paper presents experimental evidence that supports the use of bromine/bromide as a potential alternative to conventional cyanidation for gold leaching. The study evaluated a brominebased lixiviant, Stabilized Bromine, with considerably lower vapour pressure than liquid bromine. Using a rotating device, the rate of gold dissolution was determined at various concentrations of this reagent. The reactivity of pure pyrite, arsenopyrite and chalcopyrite minerals was also evaluated in stabilized bromine reagent. Furthermore, bromine leaching of gold in a number of gold bearing ores was undertaken. Results showed that significantly higher gold recovery can be achieved with bromine than with cyanide when leaching gold encapsulated in sulphides, but bromine consumption was high owing to simultaneous oxidation of the sulphides. The greatest promise for the bromine leach process was with oxidized gold ores. The recovery of gold from oxide ores with bromine was comparable to that achievable with cyanide and bromine consumption was reasonable when leaching was conducted at a near neutral pH of ~6. In the case of oxidized gold ores containing copper mineralization, it is possible that bromine consumption may be lower than cyanide consumption, since there is evidence to suggest that bromine is less reactive than cyanide with copper minerals.

Jan 1, 2014

By William R. Yernberg

SME’s Arizona Conference was held at the Doubletree Hotel at Reid Park in Tucson on Dec. 4 and 5, 2005. The annual conference is organized by the Arizona Conference Board of Directors, which represents SME sections in Arizona and adjacent areas. The conference provides an opportunity for individuals and corporations associated with mining in the region to get together once each year to discuss the status of the industry. Important topics discussed among the attendees included the price of copper, community relations and education.

Jan 1, 2006

By Paulo Sérgio Moreira

O tamanho de grão austenítico prévio é determinante na área de tratamentos térmicos dos aços, pois este parâmetro influencia sua microestrutura e propriedades. Para que o tamanho de grão possa ser medido, é necessário que antes se aplique métodos de contraste para sua revelação. A literatura relata, entre métodos desenvolvidos, dificuldades em se conseguir bons resultados em função deles serem susceptíveis a variações de composição química e histórico de processamento dos aços. Neste contexto, esse trabalho propôs métodos para a revelação dos contornos de grãos austeníticos prévios dos aços ABNT4340 e ABNT1030. Foram utilizadas duas técnicas: ataque químico e ataque térmico. Para a técnica de ataque químico, utilizou-se um reativo a base de ácido pícrico. Já na técnica de ataque térmico, as amostras foram austenitizadas de forma a promover uma oxidação controlada. Os resultados obtidos mostram o sucesso das técnicas, com destaque para o ataque térmico que se mostrou mais efetivo para o objetivo proposto. Foi possível mostrar que no ataque químico, o ajuste da concentração de HCl em função da composição química do aço é o ponto de maior importância, ao passo que no ataque térmico, a segregação química e a temperabilidade dos aços são relevantes para o sucesso da técnica.

Aug 17, 2017

By A. T. Shurick

THE NRA Administrator's casual reference to the coal code as the next "pineapple" to be fixed was a conservative estimate of his job. This thorny and adamantine morsel now looms as a critical test of NRA. A failure in coal supplies would have the gravest potentialities in the Administration's program at this time. And the loss of prestige from a breakdown of the enforcement machinery in this initial large-scale test of strength would accentuate the incipient indications of insurrection in other directions. General Johnson has had a difficult task. It involves problems festering for a quarter of a century. A succes¬sion of Presidents have been glad to tide over their respective regimens with inconclusive expedients; they have been baffled by the complexities of the technical angles and hopelessly irreconcilable concepts of powerful conflicting interests with large issues at stake.

Jan 1, 1933

By Merle Randall

Application of a new chemical spray in a mercury mine in which ore rich in native metal was causing salivation among the miners has given such favorable results that it is believed the process will be useful in other mines and perhaps in some plants where similar conditions exist. The process was originated by Merle Randall, professor of chemistry at the University of California. GENERAL PROBLEM The presence of native quicksilver in mines from which the metal is produced has long been a source of trouble and danger to the workers. Men have been sickened and some of them have been disabled by exposure to the vapors present (even in workings that were well-ventilated by ordinary standards) and to contact with dust, dirt, and moisture with which the finely divided quicksilver was mixed. Where the ore was rich and this exposure was considerable men were able to work only a few days or weeks; where the exposure was less they were weakened and subject to ailments often attributed to other causes.

Jan 1, 1942

By Rollin A. Slater

The bulk materials handling industry has served silently for years as the skeleton structure and often the central system of nerves and nourishment for the body of basic production industries. During the past two decades, this body has undergone substantial growth and mutation to meet the surging demands of our national economy for more and better products. The steel industry has been prominent in this phenomena and plants of the sixties are as unlike the second war vintage as our current crop of basketball players differ from their fathers. Steel has kept pace with spiralling demand by innovation which has resulted in new processes and improved designs which generally yield greater production from fewer units. The supporting industry of materials handling has likewise improved its techniques and currently has a new stronger generation of equipment to perform its necessary supporting function. It has been my fortunate experience to have been instrumental in the creative stages of several new steel mills which are currently in conceptual design or actual construction. Drawing upon exerpts from this experience, this paper will describe a basic approach to the selection and application of modern bulk materials handling systems to an entirely new steel plant. Specific details of past work are not available for publication, therefore, the plant described herein is a composite of ideas and will be the new plant of the Hypothetical Steel Corporation which will be located on the lower shores of the Great Lakes.

Jan 1, 1967

By Woodcock J. T

During the dissolution of gold in fully aerated cyanide solutions the CN ion is the active agent, and consequently the usual method of evaluating the dissolving power of such solutions is to determine the CN- concentration analytically. The presence in the solutions of copper and/or zinc which themselves form complex cyanides, may result in erroneous conclusions as to the free cyanide ion concentration determined by titration.In this paper the theory of titration of such solutions has been developed, and potentiometric methods have been used to follow the behaviour of complex cyanides of copper and zinc. The results for cuprocyanides show Cu (CN)s to be the most important copper complex, and in addition they explain the reported low rates of solution of gold in copperbearing solutions which when titrated in the usual way, appear to have adequate free cyanide. An explanation of the misleading value of the titration is given, and suggestions for recognition of the condition are offered. Preliminary results for zinc-bearing solutions show that there is no satisfactory end-point for the titration of CN- in excess of that in the complex Zn (CN) 4=, which dissociates to CN and Zn(CN)g-.

Jan 1, 1950

By George H. Schnakenberg

This Bureau of Mines publication describes a passive personal sampling device for N02 in air, developed by the New York University Medical Center under Bureau Grant G0133066. The sampler has been successfully demonstrated in the field and in the laboratory. In corroborative laboratory trials the agreement with reference method is excellent. The overall accuracy is approximately ±5 pct of reading to a precision of about ±l pct. All evidence indicates that these samplers should indicate the time-weighted-average N02 concentration to the above accuracy and precision equally well in the field since effects of wind velocity and relative humidity are negligible and the effects of temperature are about 0.1 pct per °F. The duration of exposure and the approximate temperature are the only data that need to be collected in the field. A two-step analysis procedure in field or service laboratory is then used to obtain the total cumulated exposure to N02 in parts per million-hours (ppm times hours), which can be converted to the time-weighted-average concentration of N02 in ppm by dividing cumulated exposure by the duration of the exposure.

Jan 1, 1976

By Tim M. Benson, Adam L. Lamanna, Carolina Martinez-Gutierrez, Mark J. Stephani

The Lower Concourse C Extension (LCE) 108-in Storm Sewer consists of a 2,797-foot long, 27 to 55-foot deep, 108-in I.D. storm sewer tunnel. Situated beneath active taxiways and a terminal apron at Hare International Airport (D), the tunnel diverts ows from existing storm sewers located within the footprint of a future satellite concourse. The project was delivered via Construction Manager at Risk (CMAR) as part of Chicago Department of Aviation’s (CDA) ongoing O’Hare 21 Capital Program. This paper presents project details, multiple stakeholder coordination, subsurface risks and challenges, TBM performance, and impacts to existing infrastructure.

Jun 23, 2024

By D Reid, A Fourie

The in-pipe treatment of slurries with polymer addition shortly prior to deposition is a noteworthy emerging technology of increasing popularity. Although polymer treatment has been shown to substantially modify and improve depositional and dewatering behaviour in a significant number of cases, the impacts of polymer treatment on geotechnical performance of tailings are less well understood. For example, certain combinations of polymer and slurry type have been shown to result in lower final densities at a given vertical effective stress. Despite these lower densities, polymer-treated tailings often exhibit peak undrained shear strengths consistent with untreated material. However, the sensitivity and/or brittleness of the material may be negatively influenced by the looser state created. Although these changes have been studied, most testing available in the literature was undertaken on relatively ‘fresh’ samples of polymer-treated material. However, significant shear may occur following treatment and prior to the commencement of settling and self-weight consolidation as the material moves down the beach.To study the effects of shearing on the subsequent performance of polymer-treated tailings, a test program consisting of consolidation, triaxial and direct simple shear tests was undertaken on presheared polymer-treated material. Materials used were identical to those used in previously published studies on the impacts of polymer treatment in a ‘fresh’ condition. Shearing of the polymer-treated material generally appeared to lessen the impacts of the polymer treatment process. However, the behaviour of the material when sheared indicated that the polymer was still impacting the behaviour of the material in some respects. The results indicate the importance of the consideration of shearing on material behaviour when planning and designing a tailings deposit where polymer treatment is to be implemented.CITATION:Reid, D and Fourie, A, 2015. Effects of shear on the behaviour of polymer-treated slurries, in Proceedings Tailings and Mine Waste Management for the 21st Century , pp 215–224 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 27, 2015

By W. F. McDermott

This paper covers the development, construction and operation of a 53-mile slurry pipeline operating in Tasmania, Australia. Special development techniques are discussed, as well as the operation of this line and its impact on transportation from remote areas.

Jan 1, 1970

By O. A. Ojo, N. Esmaeili

"The effects of brazing and use of composite powder mixture as interlayer material on hot corrosion resistance of brazed IN738 superalloy were studied. Brazing was observed to result in significant reduction in the hot corrosion resistance of the superalloy. However, application of composite powder mixture, which consists of additive superalloy powder, enhanced the hot corrosion resistance of brazed samples. It is also found that although the use of composite powder mixture increased hot corrosion resistance of brazed alloy, if the additive powder completely melts, which is possible during brazing, it can significantly reduce the hot corrosion resistance of the brazed joint. Elemental micro-segregation during solidification of the joint with completely melted powder mixture produces chromium depleted zones and consequently reduces hot corrosion resistance, since a uniform distribution and adequate chromium concentration is necessary to combat hot corrosion. This has not been previously reported in the literature and it is crucial to the use of composite powder mixture for enhancing the properties of brazed superalloys.INTRODUCTION Superalloys have been developed in response to the increasing demand for materials with higher resistance to corrosion and creep and also with higher mechanical strength at higher temperatures (Smith, 1981). Ni-base superalloys are predominantly used in manufacturing hot sections of gas turbine engine components. This is due to their high strength and corrosion resistance in extremely high temperature service environments which is typical for hot sections of gas turbine engines (Miglietti, 2009). The continuous demand for higher efficiency and output has resulted in the use of higher operating temperatures and gas pressure in modern gas turbine engines (Jahnke & Demny, 1983). Consequently, this has caused thermal and mechanical stresses which result in severe degradation and damage of gas turbine engine components due to creep, fatigue and hot corrosion (Zhang, Feng, & He, 2006). The decision to replace or repair damaged parts depends on the overall repair cost and expected life of the repaired components (Jahnke & Demny, 1983). However, in most cases, it is more cost effective to repair damaged parts rather than use a full replacement."

Jan 1, 2017

By Cleusa Cristina Bueno Martha de Souza

Nowadays in Brazil the final disposal for spent batteries include sanitary and industrial landfill for hazardous waste from domestic waste and industrial waste respectively. The problems of environmental impact caused by spent batteries had been discussed of several years, considering the fact of metals contents, like Cd, Hg, Pb and Zn. Some techniques are been proposed for recycling this type of waste in order to protect the environment while bringing also economic advantages of recovering metals. The reclamation of metals from secondary raw materials had been employed and further applications of this flexible technology are planned to the future. The processing of metals solutions involving hydrometallurgical techniques is an efficient method for recovering metals, since it provides completely recovery of metals with low energy requirements. This paper discusses the spent alkalline batteries characterization and leaching stage experiments results with sulphuric acid as leachant. After batteries dismantling by mineral processing techniques, the black powder sample produced was submitted to diffraction X-ray characterization and atomic absorption spectrophotometry in order to verify all the substances presented. Some experiments were carried on to develop a hydrometallurgical process for initial metal recovery aiming to get Zn into a soluble form on aqueous solution in order to propose the next stages of purification and recovering Zn, as electroplated deposition. The sulphuric acid was chosen not only for being cheaper than other leachants but also for improving the extraction of soluble Zn as ZnS04 form at diluted acid concentration. Batch laboratory experiments leaching procedure were conducted to determine appropriate leaching conditions from the viewpoint of maximize zinc extraction. In these tests an amount of dry powder batteries was added to different acid concentrations and solid/liquid ratio and after leaching and filtration the aqueous solutions were submitted to atomic absorption spectrophotometry analysis to verify the Zn content.

Jan 1, 2000

By V. I. Ryaboy, S. A. Kondratyev

"The paper describes influence of desorbed species (DS) of a number of xanthates and higher dialkyldithiophosphates on the collective ability of these reagents. Adsorbed on mineral DS of the reagents in the form of products of non-stoichiometric interaction between xanthates and heavy metal salts can pass to the gas–liquid interface and remove liquid from the layer between mineral particle and water surface. A high-speed video recording displays the process of spreading of DS of xanthates and dialkyldithiophosphates over water at the moment of local rupture of the water layer. Expansion of “dry” spot on the mineral surface after DS of xanthate capture and displace liquid from the layer has been proved with video images. The comparative analysis of collecting ability and dynamic surface activity of dialkyldithiophosphates shows that these characteristics are in good correlation. The forces exerted by spreading film of the reagent’s DS on liquid in the water layer are evaluated, and the water flow rate from the layer is determined. The line of the reduction in thickness of the water layer behind the front of spreading film of DS of dialkyldithiophosphates and xanthates coincides with the line of the increase in their dynamic surface activity. Their force on the liquid volume in the water layer characterizes collecting ability of the DS film of xanthates and dialkyldithiophosphates. It has been supposed that the collecting ability of DS of a reagent is a part of its overall flotation activity, conditioned by surface tension of solution and, thus, defined by the structure of hydrocarbon fragment of the reagent.INTRODUCTIONIt is believed that collecting ability and selectivity of collecting reagents is mainly governed by adsorption of a reagent at the solid–liquid interface. A few studies have shown that activity of collecting reagents at the gas–liquid interface may have deep influence on their collecting capacity and selectivity. Experimental researches have revealed correlation between surface pressure in a carboxylic acid film on liquid’s free surface and floatability of useful components (Kulkarni & Somasundaran, 1975; 1980; Quast, 2006). According to Quast (2006), it is not always that surface pressure of a reagent film influences collecting ability of carboxylic acid. For instance, pH range of adsorption of tetradecanoic acid on hematite does not coincide with pH range of high surface pressure. So, surface properties of this acid contribute little to flotation efficiency.The correlation between reagent film surface pressure and mineral floatability has been reveled for quartz and cationic reagents, too (Bleier, Goddard, & Kulkarni, 1977). Finch & Smith (1973) showed that combination of adsorption of ion–molecular amine complexes on mineral surface and high surface tension of “fresh bubbles” was favorable for flotation performance. The use of bubbles with reduced surface tension resulted in a decrease in quartz floatability."

Jan 1, 2016