The Effect of Impurities on the Electrodeposition of Zinc from Zinc Sulfate Solution Containing Antimony." (1934)

The Effect of Impurities on the Electrodeposition of Zinc from Zinc Sulfate Solution Containing Antimony." (1934)

Montana Tech Library Digital Commons @ Montana Tech Bachelors Theses and Reports, 1928 - 1970 Student Scholarship 5-15-1934 The ffecE t of Impurities on the Electrodeposition of Zinc from Zinc Sulfate Solution Containing Antimony. Emmitt L. Klebba Follow this and additional works at: http://digitalcommons.mtech.edu/bach_theses Part of the Ceramic Materials Commons, Environmental Engineering Commons, Geology Commons, Geophysics and Seismology Commons, Metallurgy Commons, Other Engineering Commons, and the Other Materials Science and Engineering Commons Recommended Citation Klebba, Emmitt L., "The Effect of Impurities on the Electrodeposition of Zinc from Zinc Sulfate Solution Containing Antimony." (1934). Bachelors Theses and Reports, 1928 - 1970. 40. http://digitalcommons.mtech.edu/bach_theses/40 This Bachelors Thesis is brought to you for free and open access by the Student Scholarship at Digital Commons @ Montana Tech. It has been accepted for inclusion in Bachelors Theses and Reports, 1928 - 1970 by an authorized administrator of Digital Commons @ Montana Tech. For more information, please contact [email protected]. !f/ebb~EL. I • '1'& EFFECT Oli' I1,TPURI'£IES ON 'fllli ELECTROD]!JP03ITION OJ? ZINC J?ROM ZINC SUL:B'ATE SOLUTION CONTAINING .ANTIMONY. ,,>~ by,' Emmi tt L.'· Klebba A Thesis Sl.l.bm:!.tted to the Department of Che.nistry in Partial Fulfillment of the ,1equiremento for the Degree of Bachelo r of Science in Metallurgi cal lJn._;ineering '70:~TA:.TA SCHOOL OF "'TI:mS BUTTE, :. O:H'.£ANA May 15. 1934 " THE EFFECT OF I~WURITIES ON T}~ ELECTRODEPOSITION OF ZINC FROM ZINC SULFATE SOLUTION CONTAINING ANTIMONY. by Emmi tt L. Klebba A Thesis Submi tted to the Department of Chemistry .in Partial Fulfillment of the Requirements for the Degree of Bachelor of Science in Metallurgical Engineering 10806 .. ONTANA 8C1fOIl, Qf MWU LI " MONTANA SCHOOL OF l'JIINES BUTTE, MONTANA MAY 15,. 1934 • - TABLE OF CONT~NTS • Introduction page 1 2 Anparatus 4 Figure 1 5 a Procedure .6 Table I 7 Table II 8 Table III 9 Figure 2. 10 a Table IV 11 Table V 12 Table VI 13 Table VII 14 Table VIII 15 Figure 3 15 a Table IX 18 Figure 4 18 a Conclusions 19 cknowledgement 20 Bi bliography 21 -1- THE EFF]~;CT OF IMPURITIES ON 'rilE 1!.:LECTRODEPOSITION OF ZINC FROM ZINC SULFATE SOL1JTION CON'r nHNG ANT IlIIONY. It has been proven by resedrch and years of experience, that before electrolytic zinc is possible, the electrolyte, as zinc sulfate solution must be prepdred as Dure as is economical. In other words, the ideal e~ectrolyte must only be a solution of one metal - zinc. Every other metal and carbon must be excluded if good. recovery and a firm deposit is to be obtained. The elect-olyte.used in the commercial production of electrolytic zinc is termed "Pure Solution", however, in reality it is impure •. The alkaline earth and alkali metals along with the more chemlcally' dctive metals are not precipitated by the procedure used in comrflerci~ practice. 'l'rie y are, therefore, allowed to build up in quanti ty. The se common impurities seem to have no effect on deposition, yet their role in the solution cannot be ignored. One thing in common to both laboratory and practice of industry is that certain imnurities in the electrolyte have definite injurious effects on the cathode deposit. Antimony is one of these notorious offenders. nfuen it is present in the solution, the cathode depo a i t is seriously affected. These effects may be as IItrees", poor current efficiency, or if a neutral solution is used, a apc n.j e deposit. fuen this -2- sponge deposit is produced, it has absolutely no refining value due to the fact that it readily oxidizes on being gen tly heated. Wi th the resul ts of thi s so called "evil I' readily reproducible, it.was decided ~t this time to .determine the "ef'fect s" of other impuri ties on these so called "features". It was decided to ascertain whether the properties ve re diminished or exaggerated by the mixing of the other impuri.ty with the antimony present in the eoLu t Loru. HE GENTS The electrolyte used in this problem was as chemically pure as was possible to obtain under the present conditions. Anaconda electrolytic zinc dust well over 99.99 per cent pure was dissolved in chemically pure sulfuric acid. Recrys talli zed cop pe r sulfate was added to the above pulp. , The addition of copper sulfate to the zinc is for the purpose of hastening the reaction between zinc and sulfuric acid. The ch em.ica'lLy pure zinc is very slow to react with sulfuric acid, b~t on the addition of copper SUlfate, metallic copper is precipitated and the hydrogen overvoltage is reduced. The hydrogen overvol t age on copper is less than one half that on zinc so the reaction goes on with great rapid ity. There is no fear o.f copper go ing in to solut ion as long as excess zinc is present. For this reason, twice the theoretical amount of zinc required was used. o , -3- The solution is further purified by the action of the copper - zinc couple which precipitates all metals noble to zinc that may be prese?t in the "d.ua t "; The volume of sulfuric acid used for the preparation of e ,'tchstock so1uti on was two and one half Ii terse The zinc consumption was 6500 grams. Copper sulfate added amounted to one hundred grams. The volume of distilled water added was sixteen liters. The solution during its preparation was frequently agitated to allow the gases to escape and ~ermit the zinc to settle. ,As soon as action ceased the liquid was decanted, filtered, diluted to the desired zinc concentration (one hundred g rams of zinc per liter), and bottled. The remain ing solids, zinc and copper, were rejected. This stock solution before dilution approximates one hundred eighty grams of zinc per liter of solution. The f~ee acid present after the reaction is about nil. Antimony was put in solution by adding a small quantity of antimony trioxide to two Ii ters of boiling zinc sulfate solution. The whole is agitated for a time and then allowed to cool. The antimony content of the solution was determined by Lowe's method, i. e., tbe permanganate titration -r ro cedur e, -4- APPAHA'rU8 The electrolyses were conducted in a tall beaker of five hundred cubic centimeters·capacity. This type was decided. unon- after other forms had been- found unsatis- factory. The cathodes' used'in this problem were exclusively of the' highest grade "Anaconda" electrolytic zinc. The small s Laba o b t af.ned were first broken into four sections. These pieces were then heated in an oil bath at 1500 Centigrade and then rolled to the desired thickness (0.0111). At this temperature,' the zinc rolls easily and doe s not crack. .The control of the bath temperature leads to the success in zinc rolling. The cathode immersion area was 9.3 square centimeters'. Thi s value was used for the sake of convenience; the milliammeter reading for trne .area of immersion as the current density per square foot. The cathode strips ':Vere two centimeters wide, ten to tNelve centimeters long, and weighed anproximately three grams. The top of the ca thod e s trip was punched so t na t the electrode could be suspended. ~ile weighing, thereby reducing the danger of stripping the "treestl and obtaining incorrect results for current efficiency. -5- Prior to deposition, each cathode was dipped in dilute ni tri c acid to r-emove all soluble salts, then ~insed in distilled water, rewashed with ethyl alcohol, ignited, and weighed. The anodes used in these determinations were of chemically pure sheet lead. There was one of these anodes on either side of the cathode. Their immersion area was appr oxi.mately one square cen timeter. Circulation was maintained by the use of an electric mechanical stirrer. Gas evolution was not considered as an effective agitator, however, it does help. There was no provision made for temperature control. The current during electrolysis was not sufficient or result in noti ceable "he ati ng ".'rhe temperature of the operation may, therefore, be considered as that of the laboratory, near 200 Centigrade. The method of cathode suspension proved by far to be best for the problem. It can best be studied from the illustration, Figure 1. ~~en electrolysis was about to co~nence, the current was turned on and the circuit was closed by immersing the cathode in the electrolyte. After about twenty minutes, the circuit is broken by raising the cathode. The cathode strip is carefully washed to remove adherent solution. The water is ashe d off with ethyl alcohol and the whole is igni ted. , '. I 9 , ,L....=-=--- ,I' I -~ 1 1'1111 \' -> --' "I I -. -, , I'I· "lj1~"-' e' I' I :;'l . tl rl t::j r-I <I> 0 1J'o'V-' / ----1 + 1.- ~--- e8 1 en • <I> r-I -1(1 'C 0 J.f <I> +> ~ 0 ~ <I> eo r-I 0"" l'il ~ "'" 1J 0 rl 0"" ttl +> <I> A +~ '" ---=-=---=-== -----"~_=_=E-=- ,--..:4:-> -- ~-..-- - - '"\._- ---_, ---_ 1- -6- A copper cou10meter cell was connected in series with the zinc cell, whi ch made it po ssi b1e to determine the quantity of current that has passed during the operation. The volume of electrolyte used in the majority of determinations was two hundred cubic centimeters. PROCEDURE The first part of the problem was mainly to determine the maximum amount of an timon] that could be resent in the solution before the cathode deposit showed defects.

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