Патент USA US2131313код для вставки
Patented Sept. 27, 1938 . , - . 2,131,313vv ‘UNITED “STATES PATENT. OFFICE." I No Drawing. Application May 24, 1937, > Serial No. 144,562 10 Claims. (01. 23-435) This invention relates to making zinc pigments; with precipitation of the zinc as oxy-carbonate and it comprises an improvement in processes by boiling the liquor, it is vfound in practice that of recovering zinc in pigmentary form from sal the oxy-carbonatecarries enough chloride to be skimmings and crude impure zinciferous mate- objectionable. vAnd the presence of manganese, 7 h 5 rials generally by extraction withammoniacalcarbonate solutions wherein the ammoniacal solution at one stage in the operation is‘ treated which often occurs, is also harmful. In a prior and copending application Serial No. 92,235, I have described and claimed a cyclic with a phosphate to precipitate manganese as ammonium manganese phosphate insoluble in process of recovering Zine Values on Which, in some aspects, the present invention is an im 10 the ammoniacal liquid; and more speci?cally it prevement. In the proeess'of the'priorgapplica- 10‘ relates to a process of recovering zinc sul?de in a state of suf?cient purity for pigmentary purposes wherein the sal skimmings are ?rst ex- tion Waste skimmings containing chlorides are extracted with ammoniacal ammonium carbonate solution in the presence of suflicient lime to react tracted by ammoniacal ammonium carbonate with the chlorides and form calcium chloride. 15 solution including recycled liquor, in the presence of some lime, the liquid is separated from the insoluble bodies, is boiled to precipitate zinc oXy-carbonate with recovery of ammonia and ex- After separation ‘0f insoluble impurities‘, the eX- 15; tract liquor is boiled to drive off CO2 and am mo‘iiia, Which are recovered, With seperatieh 0f 7 Zinev oXy-oarbonate- The oXy-oarbonate is sep cess CO2, the precipitate is separated from a arated. the mother liquor carrying considerable 2o mother liquor containing chlorides and other impurities, is redissolved in ammoniacal ammonium carbonate solution, alittle phosphate added to the solution to precipitate manganese and zinc is recovered as a substantially chlorine-free and man; soluble impurity being discarded. The preeipi-. 20 ‘ tete is redissolved in ammoniacal ammonium car honate solution, giving a further separation of ' inseiilbies which go out Of the system- The new Solution is boiled to re-pi‘ecipitete vZine OXY-CBJ 25 ganese-free zinc sul?de by addition of a soluble sul?de, best ammonium sul?de or hydrogen sul?de, the mother liquid being recycled for use in the ?rst stated operation; all as more fully here- bonate Which is ?ltered Off or. otherwise sepa- 25 rated, the mother liquor being recycled; being added to the ammoniacal solution used in ex tracting further quantities 0f the sal skimmings inafter set forth and as claimed 30 , ' This cyclic process represents certain economies In the recovery of zinc from waste material, such as the waste materials produced in the gal- in heat and materials, and has the further out- 30; Standing advantage in that the exit-Carbonate vanizing industry and known as‘ galvanizer’s,‘ waste, sal skimmings, dry skimmingi's, zinc ashes, recovered in the second precipitation issubstan tially pure, being in particular practically free of chioi‘ine- It is useful in making Zine pigments etc., and from crude zinciferous ‘materials genera 35 ally, one of the many methods thatrhave been and other Zihepreperatiehs, It is how my discovery that in such a process ammoniacal solution of ammonium carbonate; the operation is facilitated and purer products Such a solution is advantageous as an extraction agent because of its power of dissolvingfzinc oxide Obtained by adding a small quantity of a Soluble phosphate, such as ammonium phosphate 01‘ so 40 while leaving undissolved various impurities, such as alumina and iron oxide, Silica and compounds of the various heavy metals (Fe, 'Ni, Cu, Mn, etc.) .‘ dium phosphate, t0 the ammoniacai Zinc. Solu- 40‘ tion, advantageously the second solution: that resulting from the Solution of the ?rst oXy-car There is often somelittle dii?culty in Securing a . bonate precipitate. wholly complete separation of the heavy metals '45 in this operation. In particular, this addition serves to precipitate themangenese in the form Traces of other metals than of a - Phosphate insoluble in the ‘ammoniacal 45; zinc going forward may impair pigmentary values considerably. This is particularly true’ as re- liquid- Most manganous compounds are more Or - ' less soluble in an excess of ammonium carbonate but ammonium manganese phosphate is an eX' gards manganese compounds which tend to discoloration in air. 50 351 used is the extraction of the material "with an ~ g ' Extreme purity, at least as regards certain for- ception. Ventien- The fact is utilized in the present in ' - eign bodies, is required in a good and permanent By ?ltering out the manganese precipitate,_ zinc pigment. For some reason, even the pres-ence of chlorides in such a pigment is harmful. In the use of ammoniacal ammonium carbon; the second zinc precipitation from the ammoni acal carbonate solution gives a material which is not only chlorine-free but also manganese free. 55: ate solution for extracting sal skimmings, etc.‘ 50.v This removal of manganese is useful in the proc-_ 55? 2 2,131,313 ess of the prior application where there is a double precipitation of oxy-carbonate but it is now also useful in modi?ed processes where the redissolved oxy-carbonate of the ?rst precipita tion is converted into pigmentary Zinc sul?de by an addition of a soluble sul?de. In so doing, any soluble sul?de may be employed as a precipi tant. If barium sul?de be used, the zinc sul?de then carries barium carbonate which has pig 10 mentary value. In practice of the cyclic process, the ?rst stage or extraction-digestion of the crude material in ammoniacal ammonium carbonatesolution with addition of lime e?ects a substantially complete 15 solution of the zinc oxide compounds in the ma bonate or as sul?de, I have found that it is often not necessary to ?lter o?' the ammonium man ganese phosphate precipitate. This white sub stance may be allowed to remain with the zinc precipitate without adverse discoloration effect. In practice however it is usually advantageous to add phosphate during the second extraction step and to separate insoluble phosphate precipitate from the ammoniacal carbonate zinc solution. The second; precipitation'step‘ of the cyclic'proc as a pigment. As amethod of making zinc sul?de from crude zinc raw materials generally, the process of ex terial treated. Filtration separates insoluble im purities existing as heavy metal compounds to gether with silica and alumina and excess lime. The subsequent boiling of the ?ltrate with pre 20 cipitation of zinc oxy-carbonate and recovery of tracting the-oxide in‘ an ammoniacal carbonate solution and precipitating zinc sul?de from such a solution has great economic advantage over prior processes in which zinc salts of strong min ‘ the ammonia and excess CO2 leaves nearly all tion with sul?des and quantities of by-product salts formed in the’ reaction have to be disposed of. By using ammonium sul?de or hydrogen sul of the soluble chlorides and other soluble impuri ties in solution which is discarded. The precipi tated zinc oxy-carbonate has only a small con 25 tent of chloride. The re-solution of this precipi tate in ammoniacal carbonate gives a further separation of insoluble impuritiesqand any zinc which remains insoluble in the re-solution step is recovered by the return of the insoluble matter to be extracted in the ?rst digestion step. As I have found, manganese if present has a tendency to accompany thezinc in the several extraction and precipitation steps. But I ?nd that a selec tive precipitation of manganese and separation from the zinc is e?ected by the addition of a small amount of ammonium or sodium phosphate to the circulating liquid system. The complex am monium manganese phosphate is, advanta geously, precipitated by the’ phosphate addition 40 with the insoluble impurities remaining from. the re~solution of the ?rst precipitate in ammoniacal carbonate. However, if desired, it may be pre cipitated and‘ removed separately. The second oxy~carbonate of zinc solution, upon addition 45 thereto of ammonium or sodium sul?de, yields a pure white zinc sul?de precipitate substantially chloride-free and also vfree of heavy metal com pounds. The process is operated to insure a sub‘ stantially complete separation of iron in the fer 50 ric form as insoluble compounds; the phosphate addition aiding in this separation. In the ?nal precipitation of zinc sul?de from the puri?ed ?ltrate derived from the second extraction by ammoniacal carbonate, it is unnecessary to ef 55 feet a wholly complete precipitation of the zinc content of the solution. Any zinc remaining in the mother liquor after precipitation is returned to the ?rst digestion or extraction step of the process and is recovered. The soluble impurities 60 in this mother liquor, including salts of metals resulting from the sul?de precipitation, are also returned to the digestion and are discarded with the ?ltrate obtained after the ?rst precipitation of zinc oxy-carbonate. In the process the insol 65 uble impurities are separated and discarded in the ?rst extraction and the soluble. impurities, particularly chlorides, arediscarded in‘the ?l trate liquor remaining after the ?rst precipita tion. 70 - I ?nd that the addition to the cyclic system of smal lamounts of soluble phosphate aids ma terially in the puri?cationrof the zinc product. When the soluble phosphate is added to the sec ond ammoniacal carbonate extract prior to the 75 second precipitation ‘of zinc either as .oxy-caré 10 ess in which ‘the zinc is precipitated as zinc sul?de yields a product of unusual purity and stability. eral acids such as the sulfate are treated in solu 15 20 ?de as the zinc precipitant in the present process, ammonia and ammonium Vcarbonateare recov 2.5 ered and cyclically reused. Whensodium sul?de is the precipitant, soda; is removed with the solubles by return of the liquid for. cyclic use‘ in extracting zinc crudes; , V . The separation effected between zinc and man 30 ganese in ammoniacal carbonate solution by addi tion of phosphate isa valuable feature in the ex traction of crude materials generally. ‘What I claim is}, -. l. A process of »making zinc sul?de for pig ments .from crude zinc materials, which com prises extracting the material with a solution of ammonium carbonate and ammonia, boiling the solution extract to precipitate zinc oxy-carbonate, 35 redissolving the precipitate in ammoniacal, am monium carbonate" solution with vaddition of a soluble phosphate and precipitating vzinc sul?de from said solution by addition :of a soluble sul ?de. ' ' ' V > 2. A process of converting chloride-containing zinc compoundsintoa (substantially chloride-free zinc sul?de which comprises treating the chloride compound with anammoniacal ammonium car bonate solution withaddition oflime to dissolve zinc compounds, discarding insoluble matter, boil ing the solution to precipitate zinc oXy-carbonate separatingfthe pre'cipitatewith-discard of soluble matter and redissolving it in ammoniated am monium carbonate solution with separation of insoluble matter and precipitating zinc sul?de from this solution by‘addition'thereto of a soluble 551 sul?de. _ v: , ‘ . 3. In a process ofrecovering ‘zinc compounds from crude zincifer'ous' materials containing man ganese compounds wherein zinc compounds are ?rst extracted by an ammoniacal solution, precip itated by boiling the solution extract, re-extracted in an ammoniacal solutioniand reprecipitated, the improvement which comprises adding a soluble phosphate to thesecondammoyniacal zinc solu tion. .'._ 4. In obtaining 'from' impure chloride-contain ing-‘zinciferous , material-substantially pure zinc sul?de, a cyclic process which comprises extract ing the material with ammoniacal ammonium carbonate solution with an addition of lime con verting chlorides of'the material to calcium chlo ride and with discard ofinsoluble matter, boiling the extract to recover ammonia ‘and to precipitate zinc oxy-carbonatardiscarding chloride-contain 60 3 2,131,313 ing liquor, redissolving the precipitate in am moniacal ammonium carbonate solution with separation and recycling of insoluble matter, adding to this second solution a soluble sul?de to precipitate substantially pure zinc sul?de and re cycling the liquor from the precipitation to the ?rst ammoniacal extraction of impure materials. 5. In the process of claim 4, adding a solublev phosphate to the re-soluticn of zinc oxy 10 carbonate in ammoniacal ammonium carbonate solution. 6. In the recovery of zinc from zinciferous materials as commercial pigments the process of obviating the effects of manganese compounds 15 when present which comprises adding a small amount of phosphate to an ammoniacal solution of zinc, the amount being about that sui?cient to precipitate the manganese present. 7. In the process of claim 6, removing the man 20 ganese precipitate and converting the zinc into zinc sul?de. 8. In a cyclic process of recovering zinc values from impure materials by a double extraction in ammoniacal carbonate solution and reprecipita tion with discard of insoluble impurities at one point in the‘ cycle and of dissolved impurities at another point, the improvement which comprises adding a soluble phosphate to one of said am moniacal carbonate solution extracts to aid in removal of the insoluble impurities and recover ing pigment zinc sul?de by adding a soluble sul ?de for the reprecipitation from the second am moniacal carbonate extract. ‘ 9. In processes of extracting zinc values from 10 crude manganiferous materials with extraction by an aqueous ammoniacal carbonate solution, the improvement in recovering a pure zinc prod uct Which comprises adding a soluble phosphate to said zinc solution in about the amount re quired to precipitate the manganese and remov ing the insoluble manganese ammonium phos phate thereby formed. 10. In the process of claim 2, precipitating zinc sul?de from the second ammoniacal ammonium carbonate solution by addition thereto of am monium sul?de. ' HENRY SEYMOUR ooL'roN.