Show the ie flotation of oxidized di zed ores BY 0 C RALSTON AND GLUN glen L ALLIN concentration of natural sulphide ores by the flotation process has met with such success that attempts have recently been made to apply the process to the flotation of ores other than natural sulphides sulp hides As inquiries on this subject are frequently received by the bureau of mines it has been thought best to publish a summary of the results so far obtained from the experimental work on oxidized ores at the salt lake city station of the bureau in co opera tion with the department of metallurgical research of the university of utah the work has been directed by 0 C ralston assistant metallurgist of the bureau and was carried on for the most part by G L allen alien N C christensen and R W johnson also assisted with the work As above stated this paper is only a summary or a preliminary report of the experiments on the notation flotation of oxidized ores more complete details as regards the flotation of carbonate ores of lead will be given by the writers in a paper on that subject and in the near future the bureau expects to publish a still more complete discussion on the notation flotation of oxidized ores of lead copper and zinc most of the experimental work in the laboratory at the utah station has been with the oxidized ores of lead only minor atten has been given to the oxidized ores of zinc and of copper for the following reasons little success has been had with the zinc ores many others are engaged in testing copper ores so that there was no pressing necessity of experimentation with copper ores by the bureau although an attempt is being made to ordinate coordinate co the work of those who are willing to operate cooperate co to that extent and flotation of oxidized ores flotation of oxidized minerals depends upon a preliminary by any method that will convert at least the surface of the mineral particles to a sulphide of the metal this step is followed by flotation of the artificial sulphide which results in a concentration of the metallic values in the low grade oxidized ore being treated the methods of that have been investigated are as follows 1 by the use of hydrogen sulphide on either the dry or the wet crushed ore 2 by the use of solutions of the various sulphides sulp hides and compounds of sodium 3 by the use of solutions of the various sulphides sulp hides and compounds of calcium 4 by the use of sulphur vapor 5 by the use of a oil and 6 with colloidal sulphur it has been found that treatment by some of these methods will form a film of sulphide x united states bureau of mines over the surface of the particles of such minerals as lead carbonate or copper carbonate whereas in other cases the mineral particles are to the core other methods failed to give any results carbonate of lead ores all of the above methods of have been tested on a great number of car bonate of lead ores some of these ores contained silver and some contained lead as the principal metal A number of the ores have been successfully concentrated and others refuse to yield to concentration by flotation in general a high content acid soluble in an ore seems to prevent the application of and flotation the purpose of this report is to give the main features of the flotation of oxidized ores of lead as well as other ores in with hydrogen sulphide gas as applied to the lead carbonate ores it was found that the best method of applying the gas to a dry powdered ore was in a tumbling barrel with the gas inlet in the end in a glass bottle showed that the ore blackened quickly after the application of the hydrogen sulphide gas on attempting to float out lead sulphide from the ore as soon as it had blackened it was found that a low extraction of lead was obtained and likewise a low grade concentrate unless the pulp was previously acidified acidifier with sulphuric acid by acidifying acidify ing the pulp cleaner concentrates were floated but the extractions tr of lead remained low only by prolonged treatment with hydrogen sulphide gas could the extraction of the lead be raised to commercial grade with a number of ores eight hours treatment gave an extraction of over 80 per cent of the lead the use of hydrogen sulphide was considered for the reason that it can be generated quite cheaply with iron matte available at 5 to 10 per ton and sulphuric acid at from 5 to 10 per ton the cost of ali the hydrogen sulphide resulting including labor etc is between 30 and 50 per ton if this gas in combining with the metal in the ore ore produces only a superficial film of sulphide and does not penetrate to the center of the particles it might be possible to make a ton of the gas many tons of ore unfortunately hydrogen sulphide attacks the metallic particles of the ore with such avidity that by the time the latter are sul sufficiently to permit of good extraction by flotation they have also been to the core and practically a chemical equivalent of hydrogen sulphide to the lead in the ore has been absorbed even coarse pieces of ore in a bottle absorb the gas with evolution of heat and on breaking open the pieces the black coloration is seen to have traveled deeply into them owing to the fact that the value of the lead concentrate obtained is very low as compared to the amount of hydrogen sulphide necessary to it this process is not regarded as commercially practicable ti application of sulphide application of hydrogen sulphide to the ground ore suspended in water does not seem to be subject to the same difficulty true filming of the particles with a film of lead sulphide seems to take place and the extractions possible after a short treatment with the gas are satisfactory the speed of travel of molecules of hydrogen sulphide gas as compared with the speed of travel of the same molecules in solution affords an explanation of the difference in the action of the gas when applied to dry pulverized ore as compared to its action when applied to pulp suspended with water the best results on lead carbonate ores have been obtained when sulphides sulp hides of sodium were used for the agent the sodium sulphide must necessarily be introduced trod in solution and seems to cause true filming the sulphides sulp hides of sodium considered commercially applicable are the normal sulphide of sodium naas sodium poly sulphides sulp hides nasi nas and nas and the phy drate of sodium nash of these the latter the seems to be very effective fec tive as is evidenced by the quicker blackening of the pulp and the deeper blacker color formed the normal sulphide is almost as effective the seem to be the least active different ores require ten minutes to twenty four hours of contact with the solutions of sodium sulphide used depending on the properties of the ore and on the strength of the solution of sodium sulphide amounts of sodium sulphide varying from ten to twenty pounds per ton of ore are usually sufficient and should be applied to pulp containing about aboaf one ton of water per ton of ore in order that the solution may be as strong as possible during the stage of the process after a good black color has developed and the color has ceased to increase in blackness the pulp is diluted with water to a 31 or 41 mixture and floated in either mechanically agitated or pneumatic machines the market for sodium sulphide is limited but it should normally be obtainable at considerably less than 2 cents per pound the of calcium obtained by boiling powdered sulphur with slacked lime seems to be satisfactory for ores that yield easily to but is sluggish in its action as compared to the sulphides sulp hides of sodium the normal sulphide of calcium is only slightly soluble and hence its use was discontinued as a possible agent the of calcium is the most active of these reagents but has not nob been tested to any extent in this work as there is doubt as to whether it would be commercially feasible to prepare such a compound sulphur vapor tried with sulphur vapor has been tried with little success for the reason that it must be applied at a temperature above the boiling point of sulphur in order to prevent condensation of the sulphur this means that the ore must be heated to a temperature above there seems to be no difficulty in obtaining elemental sulphur vapor commercially as pyrite will give up half of its sulphur content when heated in a closed space and sulphur dioxide gas can be reduced to elemental sulphur by passing it through a heated zone in the presence of a reducing agent As lead itself is easily reduced from its carbonate form the temperature pera ture might as well be raised to th the point where the lead can be liqua ted out a reducing atmosphere being used instead of a sul atmosphere the use of a flotation oil in which loosely combined sulphur is available for combination with carbonates of lead or other metals and the rest of the oil is then available for oiling the artificial sulphide has given very little encouragement in the tests conducted by the bureau finally colloidal sulphur mentioned as a possible method of does not seem to combine with lead carbonate at all it floats as a white lining of the air bubbles in the flotation machine and brings up very little lead with it usually the precious metals contained in a lead carbonate ore accompany the lead the writers have noticed that the silver extraction will lag behind the lead extraction when the ore is with sodium sulphide and that the reverse has usually been true when hydrogen sulphide was used the importance of flotation is due to the fact that there are many deposits of lead carbonate ore in all of the western states and many of these ores have been milled with varying success frequently the lead carbonate can be satisfactorily concentrated by gravity methods but often it is found that the particles of lead carbonate go into the slimes and are lost tailing heaps containing 5 to 10 per cent of lead are common the object of this investigation vesti gation is to determine whether sulpha dazing flotation could not be applied to the treatment of the deposits of lead carbonate above mentioned to prevent the waste that now takes place when these arbs orbs ores are treated by gravity concentration processes and render amenable to treatment carbonate ores that are too low grade to be treated by present methods the general engineering company of salt lake city has carried on extensive tests of different lead carbonate ores with varying success according to the ore tested the company owns several patents which ft has either patented or purchased A flotation plant to apply and flotation to an ore containing lead ail ver and gold has been constructed by the prince consolidated mining company at pioche nevada for the treatment ot of two to tailing dumps from former pan pail amalgams tion and cyanide operations in that vicin vic ity this plant is now in operation oxidized copper ores many attempts have been made both by large operating companies and by other experimenters peri menters to float the carbonate and other oxidized minerals of copper for that reason the testing of such ores by the writers has been limited hydrogen sulphide seems to be by far the e best medium for oxidized copper ores previous to flotation when applied to the dry ore the writers found the same conditions as those mentioned for lead the particles are to the center which requires an excessive amount of hydrogen sulphide applied to the wet vet pulp the hydrogen sulphide seems to cause true filming the writers work has yielded black concentrates but they are informed by mr callow of the general engineering company that the company has been able to reduce the amount of 0 sulphur used to a point where the froth is green with slightly coated malachite he states that as little as one half pound of sulphur per ton of ore is giving good extractions in the plant of the magma copper company at magma arizona where his company has put in the first successful installation of this kind sodium sulphide has been tested by a number of the larger companies who have some oxidized copper minerals in their sulphide ores the amount of oxidized copper in such ores is usually a fraction of I 1 per cent so that two or three pounds of sodium sulphide per ton of ore are all that is necessary this is usually added to the machines during flotation or to the mixing tanks before flotation the writers experience is that if some little time of preliminary contact is allowed before flotation is attempted better of the material will result calcium has been used for some time in a number of the large copper concentrating mills with indifferent success and seems to be detrimental in some instances on the ores tested by the writers fair results were obtained it if the calcium was allowed to act until the ore had become well blackened it is stated that sulphur vapor was tested at one of the large plants for flotation ot of oxidized forms of copper and gave better betters re suits than any other method of of course this method has the disadvantage of to dried liea heated ted having to be applied and finely divided ore used at a 11 num oils are being meano ethod her ber other ni of plants to supplement is of and considerable secrecy observed as to the technical details oi of work bork so far as the writers know colloidal sul chur does not assist in the flotation of oxidized forms of copp copper er 11 neither either lias the silicate of copper been successfully floated by flotation it will blacken when but resists flotation possibly it still presents a silicate surface rather than a sulphide surface to the flotation elements for this reason a number of the large copper companies are seriously contemplating tem plating leaching the oxidized copper ores rather than lose what silicate of copper may be present repeated attempts to float the natural sulphides sulp hides along with minerals have failed as the agents cause trouble with the flotation of the natural sul aphides dy by careful adjustment this difficulty has been solved in one plant though the details are not available oxidized zinc minerals attempts to float the oxidized particles of zinc from their ores both before and after by most of the above methods have met with no success whatever in the laboratory experiments of the writers they are informed that some headway was made with the problem by prof at the colorado school of mines but that the sulphide film seemed to come off too easily however poor results were ob obtained taine d whatever the cause the writers experience has been that most of the carbonate ores of zinc contain important amounts of the silicate and this may be one reason for the nonsuccess of this work for the same reasons that copper silicate will not float direct flotation of oxidized minerals of the kind mentioned so far as known has not been successfully accomplished in all of the successful work witnessed by the writers there has been some form of alteration of the oxide to the sulphide A number of parties claim tobe to be successful in the flotation of copper carbonates without sul and others in the flotation of scheelite fluorite and magnetite the authors were unable to verify these statements |