The effect of low concentrations of isopropyl alcohol, n -butyl alcohol, isovaleryl alcohol, glycol, glycerol , glucose and starch on the rate of precipitation of alumina hydrate from metastable aluminate solution s was studied. The changes of electric conductivity during the precipitation were also measured. Only glycol accelerated the precipitation of alumina hydrate at concentrations covered by the experiments; the other substances retarded the precipitation. Glycerol in a concentration of about 0.2 M/ 1., glucose in a concentration of 6.7 g./ 1., and starch in a concentration of 6.7 g./l, prevented the precipitation

D. Pavlović

H. Iveković

T. Vrbaški

English

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CR 0 AT I CA CHEM I CA A C TA 28 (1956) 101 CCA- 16 546.621-36 : 541.18.04 The Prec1p1tation of Alumina Hydrate from Aluminate Solutions in the Presence of Some Higher Alcohols and Starch H. Ivekovic, T . Vrbaski and D. Pavlovic Institute of Inorganic, Analytical and Physical Chemistry, Faculty of Pharmacy, University of Zagreb, Croatia, Yugoslavia Received February 10, 1956 The effect of low concentrations of isopropyl alcohol, n -butyl alcohol, isovaleryl alcohol, glycol, glycerol, glucose and starch on the rate of precipitation of alumina hydrate fror:n metastable aluminate solutions was studied. The changes of electric conducti-vity during the precipitation were also measured. Only glycol acce-lerated the precipitation of alumina hydrate at concentrations .covered by the experiments; the other substances retarded the precipitation. Glycerol in a concentration of about 0.2 M/1., glucose in a concentration of 6.7 g./1., and starch in a concentra-tion of 6.7 g.fl,, prevented the precipitation. A previio u:s p.aiper by H. Iveikorvi,c, T. Vrba1skJ. aind D . Pavl,orvic1 dealt with the effrects of .aidd1irtion of metha1I1ol on the vL~1001sirty of ailruminate 1s0Jutions prior to rt:he iPTecip,ifatioil.1. of aJJUJmin.a hydrate. In 1thiis ooll11I1exrion it seemed intel'esting to ex.amillle the effect of .aloohoJis UiIJ ()IIl the rate of :precLpii.1tation of aJrum.ilna hydrate foom metastable alurrn.inaite solutions. In the pres,eint paper, the TeSIUll:ts ob11Jarlined wirth .is1oprorpyl alcohol, n-hutyl .aloohoJ, .i,sorvaJeryl .ailcoh oJ, glyco1l, .glycelI'oJ , glucose and sitairch .aire reported , whi1le the iresiuJts with lower alcohols, as well as the conclUJS.iOillS which may be drawn from the experimental material as .a w h o1le, mre J,e:f.it for a siubsequent pub1i,cati10i.11. EXPERIMENTAL Preparation of the aluminate solutions The solution of sodium aluminate was prepared in the way described in our previous .papert. Stock solutions containing on the average 1.489 M/1. Ab03 and 2.195 M/ 1. Na20 were used. The experiments were performed with solutions obtained from these stock solutions by diluting them with water and an alcohol to a final concentration of about 1.0 M/ l. Al20 3. In the case of n-butyl alcohol and isopropyl alcohol smaller quantities were taken because of their lower solubity. Measurements were started as soon as the solution of selected concentration was prepared, with addition of alcohol or otherwise, and were continued until about 60 mole per cent of the alumina hydrate contained in the solution natl precipitated. This took about 40 or 45 hours. The aluminate solutions were contained in stoppered Erlenmayer flasks, shaken all the time by a mechanical device. All the experiments were carried out in a constant temperature water bath at 30± 0.lOC. The AhOa and Na20 in the solution w ere determined by titration with 1 N HCl with tropaeolin (}0 and phenolphtalein as indicators2. By continuing the a.ddition of acid until the solution becam reddish-onion coloured, results were obtained in close accordance with those obtained gravimetrically. 102 H. IVEKOVIC, T. VRBASKI AND D. PAVLOVIC At appropriately spaced intervals o[ time samples were taken from the flasks . Only the •suppernatant liquid above the precipitate, which quickly settled when the shaking was discontinued, was taken for the analysis. During the precipitation of alumina hydrate the electric conductivity of the . clear solution was also determined. Precipitation of alumina hydmte from aluminate solutions in presence of isopropyl alcohol, rn-butyl alcohol a.nd isovaleryl alcohol For these experiments aluminate solution I was used, the composition of which is shown in Table I. This solution was obtained by dilution 100 ml. of the stock so.Iution with water, or with water and an alcohol, to the volume of 150 ml. TABLE I Comnosition of aluminate solution.~ Solution M Al20a/ 1. M Na20/1. Caustic ratio I 0.984 1.510 1.532 II 1.007 1.510 1.500 III 0.984 1.368 1.390 Referring to fig. 1, cUirves a1 - a3 show the effect of isopropy.l akohol (10 ml.), n-butyl ailcohoJ (1 ml.) ,aind isrovaleryl aJcohiol (1 ml.) resipectively on. the ~ate o,f precipitation of aJ,umina hyid:rate frOlln alurrrui111ate sol'UJtions I com-posed as shown in Table I. Ou:rve a0 relates to the ~cmtarneo~ p1rec~>Ltatiorn of aliumina hyd:rate. JO hours Fig. 1. +o a, JO fO 20 30 40 hours Fig. 2-. Figure 1. The effect of isopropyl alcohol, n-butyl alcohol and isovaleryl alcohol on the rate of precipitation of alumina hydrate from aluminate solution. Curve a 1 - 10 ml. = 0.868 M of isopropyl alcohol per llter ; a, - 1 ml. = 0.0726 M of n-butyl alcohol per liter and a 3 - 1 ml. = = 0.0610 M of isovaleryl alcohol per liter · at 30'C. Curve a 0 relates to the spontaneous preci-pitation Of alumina hydrate from the same solution. Volume of the aluminate solution was·150 ml. Figure 2. Changes of electric resistivity of aluminate solutions during precipitations of a lumina hydrate in p resence of different alcohols at 30'C. Curve ao - w ithout addition ; a, - with 10 ml. = 0.862 M of isopropyl alcohol per liter ; a, - with 1 ml. = 0.073 M of n-butyl alcohol per liter , and aa - w ith 1 ml. = 0.061 M of isovaleryl alcohol per liter. PRECIPITATION OF ALUMINA HYDRATE 103" Ln the sipon.itanoous rprocesis (ourv.e a 0), 10.0 mo1e per cent of the ailumina hydir.ate Oll"i1gin,ally ;present cim. the soliutiOIJl was !Pl'·eciipitated ilil 20 hou.rs. After 41 hiGf\.Ll's of. preo1pifatiJ01n this qu:antity amoU1I1ted to 63.6 moJe per cent. 1111 !the presence o.f the above mentioned alcohols the rate o.f prec~pi<tation <lecreaised mairkedJy (oUII'ves a1 - a 3). This, as an ex·ample, addi,tJ~on of 10 ml. of isorpropyl ailoohol fr·esuJ>ted 1n a reduction o[ the amou1nt of aJurrnina hydir.ate preci1piitaited in a redluctio111 olf ihe amo1mt of alumi111,a hydrate preoi;pitated afrter 41 holUII"S to 42.0 mole per ·~ent, additiion of 1 ml. :of n-=burt;yJ alcohol to 32.0 mole per cent, of 1 mJ.. of isovalery1 alcoh:ol fo 28.8 mole per cent. · Fig. 2 shoWLS the changes of specific eleocyic .resi1Sltiivity (1 /x) of aJ.uminate sol'Ultions, in [presence of the alb01Ve m enti1oined alcoho~. 80 20 ..'$.! t> ~60 ~ 16 . ~ E ~ v '" .§ 12 "l:I ~ ~ ~ ·Iii 's. ~ <> ·s: 8 ~2 :.:::: ..... .!'.> <:> "' <: "' .. c.. 4 " <.J ... s. a a, v ~o "' ~o 10 w JO •O 50 10 20 30 ' 40 hours hours Fig. 3. Fig, 4. . Figure 3. The effect of glycol and glycerol on the rate of precipitation of alumina l\ydrate from aluminate solution. Curve a 1 - with 10 ml. = 1.19 M of glycol per liter; a, - with 30 ml. = 3.58 M of glycol per liter and a 3 - with 2 ml'. = 0.182 M of glycerol per liter, at 30° C . . curve a 0 relates to the spontaneuous precipitation of alumina hydrate from the same solution. Volume of the aluminate solution was 150 ml. Figure 4. Changes of electric resistivity of aluminate solutions during the precipitation of alumina hydrate in presence of different quantities of glycol or glycerol at 30°. Curve ao -without addition; ·. a1 - with 10 ml.= 1.18 M of glycol per liter; a, - with 30 mL= 3.58 M of glycol per liter and a3 - with 2 ml. = 0.182 M of glycerol per liter. Precipitation of alumina hydrate from aluminate solutions in presence of glycol and glycerol For this 1rum. of ex1periment<S ailumilnate so11UJtiom. U was used, the compo-sitiion ·of which is shown .irr1 T<11ble I. Referring to Fig. 3, OUTV·es a1 1aind a2 show the effect od: glycoi {10 a1nd 30 ml.) OIIl the xaite of preciipiltati-0111 of ial.umina hydrate from al'llllnin.ate solution II com!Posed ais sihown in Talhle I. OUII'Ve a 0 relates to the S!P:ontaineo:uis p:rec.ipi,ta-tion af alumirria hydrate from alumimiate siotlutilOII1.. In foe spontaneous 1p1rocess (OUJI'Ve a 0); 12.8 moJe iper cent of the alumina by<lT.aie :oriJg,inaJy iprresent dn ·the :solution was preci.pitaied in 20 hours. After 40 hours of ;pirecipirtat·ilOIIl this qwaintity affiJOIUIIllted ·to 59.4 mo:le per cent. 104 H. IVEKOVIC, T. VRBASKI AND D. PAVLOVIC The preseilJce of •glycoil. graduai1ly in1oreaised the rates of preci'J)itatioin. On adtdliitiiotn of 3.i58 moles per hlterr ('ouirive a2 ), the quantity of alumina hydrate preoi1pitated after 20 houirs is 59.6 moil.e per cent. After 40 hours this. quantity amounts to 64.4 :mole per cent. It is a1p1pairent tooit gilyool accdeLraites col!1Jsiderahly the prr-eoipitaition o,f alurrn:iina hydir.ate in ·the first part otf the process. The difference between ·the qual!1Jt:ity of hydrate pLT:ecipitated in piresence of 3.58 mo.}es of glyoo~ per litelr ain ·the qruaintity precipi<taited s1po111taineously amoU!IlJted to 46.8 mo1e peir cent .after 20 houirs, as CO'!IllpaLred wi1th 5.0 mole per cent .after 40 hOUirn. The shaipe of t he cuirves of prrecipitaition in these cases disclosed am au toca talyitic !PI'Ocess. -! !! l_so1---+--+----l----,..l--...;;:______j ~ -~ j .:+O'f- -f----f----/-f---_,..,i:::::_-J ~ ~ :s. ~ ~W'f-----1------++-~4--+--1------" ~ ~ l ~=---!.--4-.-::=.---l--....l...2l~ ~O'--~~------,!o,-------,!o,-~l,.-__J ~ w ~ " ~ hours 10,---,.---- ,.----,.-----, Fig. 5. Fig. 6. Figure 5. The effect of glucose and starch on the rate of precipitation of alumina hydrate from aluminate solutions. Curve a 1 - 0.67 g. glucose per liter; a, - 0.67 g. starch per liter ; a, - 6.7 g. glucose per liter and a, - 6.7 · g. starch per liter, at 30° C. Curve ao relates to the spontaneous precipitation of alumina hydrate from aluminate solutions at 30° C. Volume of the aluminate solution was 150 ml. Figure 6. Changes of electric resistivity of aluminate solutions during precipitation of alumina hydrate in presence of glucose and starch at 30'C. Curve ao - without addition,; a1 - 0.67 ~· glucose per liter ; a 2 - 0.67 g. starch per liter and a,-a, - 6.7 g. starch and glucose respecti-vely per liter. Volume of the aluminate solution was 150 ml. Moreover, 1it wais fu1UJI1Jd tihat glycerol ·iin a 001!1Joen~ati1oin ais low ais 0.182 M/l. completely imilhirted the preoipitaition of alumiina hydiria1te from alu:miinate so1utio[1J.S. Figuire 4 shows the ch(l[}Jge in speoi1:fuc ffi·ectric resisrtivity .(1/x) of aluffiinate soluti0tnJS in p11esence of gilycol and .gJycerol. Precipitatvon of alumina hydrate from aluminate solutions in presence of glucose and starch Fo1r thiis ll'IU!ll ,of ex.periments a,l:umiiilate solution III was 'UIS<ed ('Daible I) . ReferLring r1Jo Fi1g. 5, aucrwes a1 and a 2 sihow the lirn11ueince of glrucos,e (0 .67 g./.l.) aind s;tairich {0.67 g./il.) on the 1raite of precip.ttati:on of aJumina hydrate-PRECIPI'TATION OF ALUMINA HYDRATE 105 frOIID ,a1umJ.il11ate sol1urti1on III haivi1n:g a compmi1tio!!1 sihiown 11!1 TalbJe I. CUJI'Ve a0 relates to the spontaneo1us ;preoi1pi:ta1tirn1. lin the sipontain00'111S· 1p1rocess (auirve a0 ) , 12.8 mole per cenit of foe aJumina hydrate ,cjrJiginially 1p;rese!l1t in the s oJutiol!l wais pirecipti,tated in 20 hoUTS. After 40 horurs this quantity amowl'ted rto 40.8 mole per cent. In the pres'enoe of 1gliucoise ail11d srta!I"ch, the raite io.f IPLrecirp,i,tation of .alumina hydr arte frOIIIl ailiuimi111a1te soiliutions was comiidera'bly :dimi:ni1S1hed (curves a1 and 0 2 ). On addiitioin of 0.1 :g. of glucose fa the .aJiuimiina:te soiliuHon (curve a 1 ) , the quarutity of ,aJiumiina hydrate p['ecipitated .after 20 hO'Uirs was 6.2 mole per cent; after 40 OOu.rs of preoiipitatia:n this qiua:ntiity aimoU!Il!ted to 40.8 mole iper cent. On addliition of 0.67 g. of srtaroh per hter to the alwnina:te soJJution (curve a") the quantity of alumina hydtrate ipreci;pifated a1£ter 40 hoU!rs was 23.4 mole per cerut rntly, where as after 20 hoium no precipirtation .took place. The differences between the qiua111:tiity of .ailmnina hydrate precipitated in presence oif gi1ucrnse and sta1rch, a:nd the quantirty preciipiitarted spontan1eousJy wais, a£ter 20 hoU!I's, 6.6 moile pe1r cent 'iir1 presence of starch. After 40 hou.rs of 1p1recipiitation this difference amounted to 18.8 moJe per cent ii!l the presence of ghrcose a1J1Jd 36.2 mole !Per ce1111t ,iJTI. :the presence of !Starch. The shape uif the curves :reve:a:Js, as in the !P'revious cases, an autocatalytic process. Oo111centraitions of 1g,1Jucose of stall'ch ~1uperior to 0.1 g. per 150 ml. of alu-minarte so.lution. covresp:01J1Jding to 0.67 ,g.fl. sta1billiized the alumi:nate solution t o such an extent, that no p1reci1p1fa.tion tuo!k ,place even after 600 hours (cf. CUI'Ves a3 and a4 , Fig. 5). These experiments may have some sigini.fica1nce for the a:Jium.iina prodiuction by the Bayer's process if s:tarch is .added before or after the extraction of bauxite to accelerate the settling up of the red mud. Fiigiure 6 shows •the ahaniges of spec~fic electric resisti'Vity (1/x) of aluminate solutions Jin iprnse:nce of glucose a!Ild stairoh. REFERENCES 1. H. I v e k o v i c, T. V r b a s k i and D. P a v 1 o v i c, Croat. Chem. Acta 28" (1956) 41. 2. E. Herrmann, Arhiv kem. 21 (1949) 218. IZVOD Izlucivanje aluminijevog oksihidrita iz aluminatnih luzina u prisutnosti nekih visilr alkohola i skroba H . Ivekovic, T. Vrbaski and D. Pavlovic Ispitano je djelovanje malih koncentracij a izo-propanola, n-butanola, izo-· pentanola, glikola, glicerola, glukoze i skroba na izlucivanje aluminijevog oksi-hidrata iz metastabilnih aluminatnih luzina. Za vrijeme talozenj a mjerena je i elek-tricna vodljivost. Kod koncentracija upotrebljenih u pokusima samo glikol ubrzava izlucivanje alurninijevog oksihidrata, dok ostale navedene tvari usporavaju izluci-· vanj e. Glicerol u koncentraciji od cca 0.2 M/l., glukoza u koncentraciji od 6.7 g./L i skrob u koncentraciji od 6.7 g.11. potpuno spreeavaju iz,lucivanje. ZAVOD ZA ANORGANSKU, ANALITICKU I FIZIKA LNU KEMIJU FARMACEUTSKOG FAKULTETA SVEUCILISTA U ZAGREBU Priml jeno 10. februara 1956. 

The Precipitation of Alumina Hydrate from Aluminate Solutions in the Presence of Some Higher Alcohols and Starch

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