US1295080A - Extraction of zinc. - Google Patents

Description

H. L. SULMAN L H. F. K. PICARD.

EXTHACTION OF ZINC. APPL'lCATlON FILED JAN.20. 1917 ,i295,080 Patented Feb.1s,1919.

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HENRY LIvINGsToNE sULMaN AND HU LoNDoN, ENGLAND, AssIGNoRs To LIMITED, or LONDON, ENGLAND.

GH FITZALIS KIRKPATRICK PICARD, 0F

THE METALS EXTRACTION CORPORATION EX'IRACTION 0F ZINC.

Letters Patent Patented Een. is, rara.

Application led January 20, 1917. Serial No. 143,448.

To all whom t may concern: y

Be it known that we, HENRY LIVINGSTONE SUL'MAN,`a subject of the King of England, and HUGH FITzALrs KIRKPATRICK PICARD, a subject of the King of England, both residing at London, England, have invented certain new and useful `Improvements in the Extraction of Zinc, `of which the following is a specification.

This invention is for improvements in or relating' to the extraction of zinc from ores or zinc-containing materials, and it refers more particularly to the preparation of a solution of zinc by dissolving the metal from the ore or other material containing it with an acid. It has for its object to overcome certain diiiicultieswhich are met With in carrying out such a process.

It has previously been proposed to treat a zinc ore or zinc-containing material with an acid such as sulfuric acid to dissolve the zinc and form a solution thereof for treatment by electrolysis. In such a process the orc, if a sulfid ore, must be first roasted to convert the sulfid into oxid.

In extracting' zinc from an ore or zinccontaining material with acid a difficulty is experienced in completely neutralizing the acid with which the ore is treated, and thereinthe form of roasted fore in fully extracting the zinc from the ore added thereto. For example if a solution containing 10% of acid has "zinc oxidv zinc-bearing ore added to it in quantity theoretically sufficient to neutralize all the acid, it is found that complete neutralization is not readily obtained, the last portions of acid. remaining unneutralized even after agitation for some time with an excess of roasted ore. In practice the additions of roasted ore to acid solution are made in successive small quantities, with vigorous agitation; but such neutralization is not eicient below 1 or 2% of residual free sulfuric acid, and when approaching this limit it is preferable that the mixture be agitated for longer periods than were necessary for the previous ore additions to the stronger acid solution. l lt is also an object ofthe Vpresent invention to overcome this difliculty, and according to this invention the. neutralization of the last portions of the acidl with Whichthe ore is treated is quickly completed bythe addition of zinc hydrate.4 l.

`One method df carrying this invention intoeffect will now be described withreference to the accompanying drawing which represents the process diagrammatically for the production of a zinc salt solution for subsequent treatmentby electrolysis. A' zinc sulfid-.containing ore is'roasted to convert the yzlnc into oxid and partially sulfate, and

after grinding is added in successive portions to a 10% solution of sulfuric acid. When after such additions in'kdue amounts the liquor is found offree acid, the neutralization is completed by the addition of the requisite quantity of zinc hydrate obtained in the manner 4described below. The mixture is submitted 'to a short agitation to neutralize completely the acid. Where soluble silica is present the solution -isA preferably agitated and maintained at a temperature of from 90 to 100 C., so that the soluble silica is caused to be precipitated in a more granular form whereby it is prevented from /ge'latinizing and from causing' trouble in filtration or even the complete jellication of the liquor. The solid material is then separated from the liquor in a filter-press or vacuum or other suitable filtration apparatus, `and the clear liquor may be passed over lgranulated metallic zinc, or preferably agitated with zincfume, to remove any copper and cadmium present.

The material left in the ltenpress is the ore, viz. silica undissolved portion of the gangue-stulf, linsoluble lead and other Inetallic compounds, ferrie oxid, gelatinous silica', etc., but still wetted with some strong zinc sulfate solution.

This is recovered as with water, but the zinc sulfatesolution so obtained is necessarily too Weak and too voluminous to be added t0 the main bulk of the filtra-te, which in a cyclic -electrolytic proc-v ess, must be kept'at the `strength'. and volume suitable for the final electrolytic precipitation of the zinc; from 8% to 10% of zinc as sulfate is a desibe electrolyte. In order to prevent the accu `ulation of large quantities of these weak liquors and to avoid y to contain from 1 to 2% usual by washing-out the necessity of concentrating themand their zinc contents by evaporation, We Atreatthem in a suitable tank or vesselwith strong agi-4 tation with the requisite quantity of milkv whereby zinc vhydrate and calcium 0f lime.

v'of the copper present'is submitted to velectrolysis for the p "j separation of the zinc until the solution con- 25 f is returned for the treatment of a fresh quansulfate are precipitated. The pulp is then filtered, the Water now free from zinc being run to Waste. zinc hydrate, which is very readily soluble even' in dilute acid, thus forms an excellent material for completing the neutralization of an'original mixtureof ore and, acid which cannot, as stated, be completely or efficiently neutralized by roasted ore additions; and

tains about 10% ofv sulfuric acid, When it tityof roasted ore to neutralize its acid content andreplenish its zinc.

' Various modifications may be made in the process Without departing fromthis inven-f tion. For example if alcarbonate ore is to be treated, it is not necessary to submit it containing material include zinc ores. l A 1 What We claim. as our invention and deto a preliminaryroast before treatment with the acid. 'y

In the following claims the term zincis to be understood to sire to secure byLetters Patent is 1.- In aprocess for the extraction of zinc I from zincfcontaining material treating the l lteringl the clear solutions from the residue, l

material'with acid to dissolve the zinc,

The precipitate containing to 'be re-l Washing the residue to remove the solution remaining therein, adding milk of linie to thel said Washings to precipitate zinc hydrate and adding the precipitate so obtained to the solution produced from a fresh-batch of zincco'ntaining material'by treatment with acid to (omplete quickly the neutralization of the aci Q2. Ina process for the extraction of zinc from zinc-containing material in Which the materia-l is treated with an acid, complet-- ing the neutralization of the acid by the Aaddition to the solutions of zinc hydrate andV agitating the vmixture of zinc-containing liquor and maintaining it at a temperature of from 90 to 100o C. to causethe gelatinous silica to separate in 3. In a process for the extraction of zinc from zinc-containing material treating the material with acid to dissolve the zinc', ing zinc hydrate to neutralize quickly the remaining acid, agitating the mixture and maintaining it at a temperature of rom`90 to 100o C. to cause the gelatinous silica to. separate, the residue, Washing the residue to remove the solution remaining therein, adding milk of lime to the said Washings to precipitate `zinc hydrate and adding the precipitate so obtained to the solution produced from a fresh batch of zinc-.containing material by treatment with acid to complete quicklytheneutralization of the acid;

In testimony whereof We have signed oui` names to this specification inthe presence of two subscribing Witnesses. v A

HENRY LiviNGsroNi. siiiiiiiii'.A HUGH riTziLis KiiiKrirRicK riolen.

Witnesses:

ALFRED l\liri"rii -1e,r HERBERT S, BURSLEY.

a more granular orm.-

material residue and neutralized ada y

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