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Experimental Study on Formation Conditions of Ammoniojarosite and Its Environmental Significanc

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维普资讯 http://www.cqvip.com V0lJ 80 No2 pp。296—30l .ACTA GEoLoGICA SINICA 2006 Experimental Study on Formation Conditions of Ammoniojarosite and Its Environmental Significance WANG Changqiu ’,MA Shengfeng ,LU Anhuai and ZHOU Jiangong 1 School of Earth and Space Sciences,Key Laboratory of Orogenic Belts and Crustal Evolution,Ministy rofEducation,Peking University,Beijing 100871 2 National Research Center of Geoanalysis,Beijing 100037 Abstract:Formation condiitons of ammoniojarosite in system Fez(SO4)3-(NI-U)2S04-H2O are investigated in this paper.The results show that ammoniojarosite can be formed rapidly under normal temperature and pressure by controlling suitable pH value and Fe2(SO4)3 and(NH4)2SO4 concentrations.The pH value,temperature and concentration of Fe2(S04)3 medium are keY factors influencing the formation of ammoniojarosite.Under normal temperature,precipiattion of ammoniojarosite can be seen within 24 hours at pH values between 2.t;_-3.1.and a great quantity of ammoniojarosite is formed within 48 hours.At about 90。C.the pH value range forming ammoniojarosite extends to 1.:!-_3.1.and within this range the rise of pH value is advantageous to the formation of ammoniojarosite and high Fe2(S04)3 concentration is also advantageous.Rdative pure ammoniojarosite is synthesized under high Fe2(SO4)3 concentration( :o.05 M)and ammoniojarosite containing melanterite and colloid amorphous hydroxide vitriol iron is formed at low Fe2(SO4)3 concentration.The deposition process of ammoniojarosite can be used to harness wastewater from ines and other mindustries and remove S,Fe and other toxic and harmful elements,such as As,Cr,H2. Pb in water.Rapid formation of ammoniojarosite and other jarosite analogs under normal temperature and pressure has a good potential prospect for harnessing acid wastewater by means of precipiatiton ofjarosite and ist analogs. Key words:ammoniojarosite,formation condiitons,harness of acid wastewater,environmental significance 1 Introduction removing iron in the metallurgical industry are carried out at 80-90。C.Under norma1 temperature and pressure. Ammoniojarosite((NH4)Fe[SO4】2(0H)6)is one of the minerals often used in the jarosite method applied widely to remove iron in the wet metallurgical industry.The principle of iron removal in wet metallurgy is that at a certain temperature and acidity and in presence of ammonium or alkaline metal cations,Fe“in solution is deposited as synthesis of ammoniojarosite needs a period of several months with a very small amount of products(Zou.1 998). This paper investigates experimentally the chemical synthesis conditions of ammoniojarosite,especilaly the formation conditions and influence factors under normal temperature and pressure,and discusses the environmental jarosite or its analogs,so as to be removed from the solution since jarosite and its analogs are indissolubility in thin acids and can be easily deposited,washed and filtered.In fact。 signiifcance of the formation of ammoniojarosite and its analogs. such a property of jarosite and its analogs has important application significance and good prospects in environmental science. 2 Experimental Method Like other jarosite—group minerls,ammoniaojarosite is formed in an endothermic reaction that runs slowly at normal temperature.Therefore.either the previous synthetic experiments or actual precipitation processes Corresponding author.E-mail:cqwang@pku.edu.cn In experiment,at ifrst sulfuric acid,ferric sulfate(solid’ analytic grade),ammonium sulfate(solid,anal【ytic grade) and ammonia water reagents were used to prepare acidic fe c sulfate with a certain concen ̄ation.05 M .mmonium sulfate aand ammonia water solution with a volumetric ratio of 1:3.Next.a certain quantity of acidic ferric sulfate solution and an appropriate amount of 维普资讯 http://www.cqvip.com VO1.80 No.2 ACTA GEOLOGICA SINICA April 2006297 ammonium sulfate solution were put into conical flasks. After shaking well,the mixed solution was adjusted for pH value by ammonia water solution and kept in a temperature.controllable oven.After reaction for a certain period of time under different temperatures,pH values and media concentrations,the mixed solution would be precipitated to form ammoniojarosite,which were filtered hten,and the precipitates obtained were dried naturally and naalyzed by the XRD and SEM to investigate their components and aggregate morphology.The pH values of hte experimental solutions were determined by a pHs-2C digital pH meter.SEM analysis was performed on a XL3O SFEG Scanning Electron Microscope in the School of Physics,Peking University.XRD analysis was carried out on a high-power f 1 200 kV)rotating anode X-ray diffractor (RIGAKU-RA)made in Japan in hte College of Chemistry and Molecular Engineering.Peking University。with naalytic conditions:CuK0【radiation.scan range 20 from l0。to 70。and scan step 8。/min. 3 Results In the light of the experimental investigation of formation conditions ofjarosite(Wang et a1.,2005),siimlar experimental conditions were monitored in chemical synthesis of ammoniojarosite. 3.1 Effect of temperature A certain quantity of thin sulfuric acid with pH about 2.00 was made up using concentrated sulfuric acid and deionic distilled water.Next,three ferric sulfate solutions with concentrations of 0.1 M.0.067 M and 0.O5 M were compounded in conical flasks撑1.撑2 and撑3 by dissolving 4 g ferric sulfate solid reagent in 100,150 and 200 mL thin sulfuric acid,respectively.Then。the alnlTlOnia water solution was used to adjust hte pH value of the ferric sulfate solutions in conical flasks撑1.撑2 and撑3 tO 2.78.2.01 and 1.71。respectively. The solution in conical flask挣1 changed rapidly its color from light yellow to orange and became turbid gradually. After standing for 3 hours at room temperature,some light. yellow precipitates speared on the bottom of lfask撑1.and precipitates were hardly seen in flasks撑2 and撑3. After flasks撑2 and躬were put in the oven with a constant temperature of 90。C f0r 2 hours.some light yellow precipitates appeared and the solutions turned dark in color.We kept the two flasks in room temperature.in which the solutions became light and some yellow precipitates were separated out in the flasks.The precipitates obtained after filtering of the solutions were dried naturally under room temperature for several days. nad they looked like earthy aggregates.Next,the prceipitates were identiifed by the XRD(Fig.1a), indicating hteir ammoniojarosite imneral phase. The experiment shows that temperature plays an important role in the formation of ammoniojarosite.At room temperature,ammoniojarosite can be tormed in system Fe2(504)3-(NH4)2504-H20 in a short time(severla hours)at pH 2.78.whereas it cannot be formed from the same system in several hours under lower pH values. However。while the system iS at higher temperatures,for example 90。C。ammoniojarosite can be crystallized out at lower pH values.This is because ammoniojraosite is formed through an endothermic reaction and high temperature is advantageous to its formation. Comparing SEM images(Fig.2)of ammoniojraosite nad iarosite from solutions with 0.O5 M ferric sulfate at 90。C,it can be seen that both ammoniojarosite and iraosite synthesized at relatively high temperature display a relative even grain size and are dispersive,in which almost no lfocculent colloidal minerals and grain polymerization occur. Moreover,ammonioiraosite and iraosite have different grain shapes,relative ideal pseudo.octahedral rgains for the former while spherical grains in the main for the latter。which is consistent with the result given by Sasaki and Konno(2000). 3.2 Effect of pH value A certain quantity of htin sulfu【ric acid with the pH value lower than 2.OO was made up using concentrated sulfuric acid and deionic distilled water.Next.a 0.O5 M ferric sulfate solution was compounded in conical flasks桴4 and other two 0.1 M ferric sulfate solutions were compounded in flasks撑5 and撑6 by dissolving 4 g ferric sulfate solid reagent in 200 and 10o mL thin sulfuric acid.respectively. Then.1 0 mL 0.5 M ammonium sulfate solutions were added into each flask and the ammonia water solution was used to adjust the pH value of hte solutions in conical lfasks 撑1,挣2 and撑3 tO 2.66,2.04 and 1.96,respectively.Through shaking well and standing for 24 hours under room temperature。some yellow precipitates that is indissoluble in thin acid appeared on the bottom offlask and there is lamost no change in flasks撑5 and撑6.Tlle pH values ofthe solutions in flasks}}5 and撑6 were adjusted to be 2.76 and 2.83 respectively by ammonia water solution.yellow precipitates appeared on the bottom of both flasks.The precipitates from filtering the solutions were dried at 5O。C and analyzed by the XRD fFig.1b).The result shows that the precipitates were light yellow earthy aggregates of mamoniojarosite. The filtrates from the above experiments were put in several conical flasks and their pH values were adiusted with ammonia water solution.When the pH value was 2.92. the filtrate was light orange in color,from which yellow precipitates were formed within several hours.The precipitate filtered was dried naturally and identified by the xRD,indicating that ammoniojarosite was its minerla phase.When the pH value was adjusted to be 3.10.the 维普资讯 http://www.cqvip.com

298 ‘rH]0 7 90 L 7110fl ^ A 4000 A nlj=2 8f pH 2l ^ 』 30{I 、 A A A A .缓. 30 40 20(1 5 A 25tl 4 A 时 一 pl卜j 48 臣200 J l 、I 50 i h ll Iprecipilaliltn under differenl synlhetic COnt.[ith}ll s ll Il1II n d 7 precipitale"2 ̄aS brownish yellow lnd the solution WHS orange that is lighter thaa the coh)l of the soluti,un at pH 2.92 The precipitate wag d ried naturally and analyzed by the XRD The result indicates Lhtlt lh p Tecipitate is illade  fFig lc)When the pH values were adjusted I‘)he 3.48 and 4()O・the pJecipitate,s wel-e brown and solutilms were nearly colorless.The precipitates we re dried and analyzed by the XRD.indicating that they are girm{hite cFigId) The above experiments indicate that ander n0nna1 mainly of ammoniojarosite and secondaril3 of g【 ̄ethitc 维普资讯 http://www.cqvip.com 一∞ u一扫IsIIoluH Vo1.80 No.2 ACTA GEOLOGICA SINICA 600 700 600 ∞ 500 500 400 邑400 嚣300 300 200 200 100 100 0 0 10 20 30 40 50 60 70 7000 10 20 30 40 50 60 70 2 (。1 A 2 (。1 5000 6Ooo 4000 ∞ 凸一 一5000 ∞ 凸一 U U 4000 3000 暑3000 __2000 2000 1000 1000 0 0 10 20 30 40 50 60 70 10 20 3O 40 50 60 70 2p(。) 28(。) Fig.3.XRD patterns of preci[}itates under different Fe2(SO4)3 concentrations A—ammoniojarosite;H—hydronium jarosite;M—melanterite. temperature,precipitates yielded from ferric sulfate solutions with the same concentration are varied obviously the flasks,respectively.Next,the solutions were adiusted pH value to 2.78,2.76.2.72 and 2.70 separately and stood nd areacted or f48 hours under a temperature of 25。C.Tllen he precipittates from ilterfing solutions were dried naturally and investigated by the XRD and SEM. The XRD analysis reveals that precipitates from at di能rent pH values.While the pH value is between 2.60— 3.10.ammoniojarosite could be synthesized within 24 hours and a large quantity of ammonioiarosite is precipitated within 2 days.These ammonioiarosite looks like earthy aggregates.When the pH value is 3.10,minor solutions with lower ferric sulfate concentrations(Fig.3a, b1 have low crystallinity and contain colloidal impurities. goethite precipitate begins to form except for major ammoniojarosite,but when the pH value is higher han t3.48, lmost only goetahite is deposited.Moreover,under normal temperature, reaction forming precipitate proceeds Their components includes ammonioiarosite,hydronium jarosite(H3O)Fe3(S04)2(On)6,melanterite FleSO4"7H20 and colloidal ferric sulfate,whereas those from solutions with comparatively high ferric sulfate cOncentratiOns have good crystallinity and simple components,mainly relatively fast at PH values between 2.9 and 3.0.and relatively more precipitate is obtained within the same erpiod oftime. ammoniojarosite and secondarily hydronium jarosite(Fig. 3c,d). 3.3 Effect of ferric sulfate concentration Ferric sulfate solutions with concentrations of 0.0 1. The SEM images(Fig.4)of the precipitates display a tendency to the XRD patterns.The precipitates from solutions with low ferric sulfate concentration show 0.0l5、0.05 and 0.1 M were made up in four conical flasks by dissolving 2,3.10 and 20 g ferric sulfate solids in 500 mL thin sulfuric acid,respectively,in which l 0.1 5,20 and 25 mL 0.5 M ammonium sulfate solutions were added into colloidal crustose aggregates(Fig.4a,b),which can be seen with the naked eye and crystalline grains can hardly be seen,whereas those from solutions、vitIl lligh ferric sulfate 维普资讯 http://www.cqvip.com

F‘,rc1¨1li‘ln L1I ^l11l-1{1盯1t :ln1 lle a Jld lI El1"Yirormlenlal Sibmil]ca[1ee —Fig 4 SEM images of synthesized alnmonioarosite ,(.1】lh】{c'j alld ed}show SEM images f1『s).nthenized JllllllO ̄inl 1isiI )l .II.15Ⅲ I[)j M respecti,,ely COfleentrakiOlt display good crystal,,with pseudo—cubic 01 synthesized a1 d displays earthy aggregates ulxder high Fe! fSO l concentration(≥O.05 M l,whereas aggregates of an1]nonioial‘osile eonla】ning fileIanlerite and c0【[old 】1lorphous hyd FOXide¨triol iroll are rmed and yields pseudo—octahedral shapes and dOlllaill illiflo r col[oidal aggregates Fig 4c.d 4 Conclusions and Discussion The e ̄per】men LaI resulls h'r chemi0a J sv[1thesl of cruSIOSe after diyln na(urallv at 1ow Fe、fS( lI c0ncentrati,.1 rl Conlrasled wilh iarosite hav【n sphedcal Iai1rH al1lnlflI1ioiarosi ce has good crvstaI1i11jty and oflen exis[ as pseudo—t211bic and pseudo—tKtahedraI grains aillnlOllJO aros】le show lhal anlmo[1iqjalOS【le c n be t-Orlll ̄d rapidly under nornlal(elllperature and presstue by cofltrolling suitable pH value and FezlSO Jl and f H SO4 concentrations The pH k,alIJe. mperature and Under tle same condition.anlmoniojamsite Call be formed less Iii quantity than Jarosite in the saflle lime. A 1aro ̄,j[e a[1aloes are lndiSSOlUbIe m d Iuled acid and precipitated I'iltrate ̄I and washed easily they ate widely Concentration 0r Fe、^S0 h medium are key 1actore; Infl Llenc.『1g 1 rl/latioi1 0 Jl alf1monioilfl( 、]【c Urider ilorn|aI Leillpera[LI r prempltatIO11 l_t anlmDnio]aiosI carl be een tJsed In iton rerllok.a1 iit wet metal1urgical li1dusir},attd developed iflto a speciat method:the Jarosite precipitation method Acltta_】v the properlies ol’iaroslte analoes presenl withi11 24 hours whDr1 pH va】u[1 al’c belwcen 2.6--3.】and a great口LJH[1[1tV 0r a1 5"11-11onioja, c) Ile I imed wjthjn 48 NI1Ing a good prospect for hm-1[essing acId wastewater f Hn lnjife alld olhei Indus Lries.so the stttdx,of iarosite a rlalogs has a polc[1tia]ellvironmental significance. A、far a larosite COllCerlled.the mali1 chemicaI hours A【about 90 C.the PH k,a Jue FaD e amIq]O[1iojarosite exlends In I 2—3 1.and withln this Iaflge. the rise of pH valuc ls advantage{11 tO the I ̄)rl1.【f【i011'Ir ammoniojarosite and l1I Fe、tSO J{collcentralio[1 a1NO ad'va[1tageou . Re1at s'eIv pL[1 e allllflOrlio arosite ls c【)兀1posit『(Ills are lee and K besides S0j.descr/bed bv KF IS0j】 {O]-l1^There are ollen Na .NH4一 Ag .HjO一.TI 维普资讯 http://www.cqvip.com Vo1.80 No2 ACTA GEoLoGICA SINICA A 301 .and so on to substitute K and Crn,V“,even lanthanides occurring at the Fe site.Furthermore,besides respective univalent nad trivalent cations substitute each other at hte K and Fe sites.there are still bivalent cations Cd ,Ba ,Pb , Hg2+.etc.occurring ta the K site(Dutrizac et a1.,1996).For the balance of electrovalence,there would be some bivalent cations substituting trivalent cations or vacant sites at hte K site in the case of some bivalent cations occurring at the K site.Moreover,[so4】2-can also be substituted partially by complex anions[Set4】 一,[CIO4] 一,[PO41 ,[msO4] 一,[CO3】 2-,[SbO4r,[Sit4】4-,etc.(Baron et a1.,2002;Prieto et a1., 2oo2:Courtin.Nomade et a1.,2OO3;Drouet et a1.,2003). Therefore,the formation of iarosite naalogs can be used to ifx and remove many harmful elements,such as S,As,Cr, H Pb in wastewater because of their well developed isomorphism. A good experimental effect of treatment has been obtained by utilizing the formation of natrojarosite and peroxide oxidation to pre.treat highly concentrated sulfur wastewater containing sodium from a factory in Jiangsu, which effectively lowers the sulfur content and COD value of the wastewater and makes the treated wastewater meet the demand of the subsequent biological treatment(Ma et al,2005).Furthermore,a good chromium removal effect also was obtained by using the formation of iarosite and ammonioiarosite to treat simulated chromium wastewater (Ma,2005). Acid imne drainage is one of the maior wastewater that causes environmental pollution.Such drainage,whose pH value is smaller than 5 or even as low as around 2,can dissolve many elements,not only a large amount of water soluble elements such as Fe,Mn,Ca,Mg,Al,SO ,but also some poisonous and harmful elements,such as Pb,Cr, Zn,Ni,Co,As,Cd.This wastewater makes water change color,turbid,pollute surface water and groundwater and causes water and soil ecological environment deteriorated greatly. Actually,the main chemical compositions HEO,Fe“. SO —in acid mine drainage are the main chemical composiitons for forming iarosite analogs.If chemical compositions,such as K,NH4,which are needed in the formation of iarosite naalogs nad scarce in wastewater,are brought to acid mine drainage,and appropriate pH value, medium concentration,temperature,etc.are adjusted to make hte chemical composition rapidly ofrm precipitates of iarosite analogs,sulufr in wastewater would be removed. Moreover,during the process of colloid precipitation of iarosite analogs,poisonous and harmful elements in wastewater,such as As,Cd,Hg,Cu,can be fixed or removed by co-precipitation(Lin et a1..1 997;Courtin- Nomade et a1.,2003).The treatment of acid wastewaters fromminesandotherindustries oftenneedtobe carriedout in a natural normal temperature condition,and our ammoniojarosite formation experiment indicates htat rapid formation ofthis kind ofmineral in normal temperature is feasible. Acknowledgements hTe authorsthankProf.ChenTianhuandWangNingfor hteir constructive reviews of this manuscript.This study was financially supported by the National Key Program ofr Basic Research ofChina(No.2001CCA02400). Manuscript received Nov.1,2005 accepted Dec.20,2005 edited by Liu Xinzhu References Baron。D.,and Palmer,C.D.,2002.Solid-solution aqueous- solution reactions between jarosite(KFe3(SO4)2(OH)6)and iIs chromate Analog.Geochim.Cosmochim.Acta,66(16): 2841-2853. Courtin—Nomade,A.,Bril,H_,Neel,C.,and Lenain,J.F.,2003. Arsenic in iron cements developed witIlin tailings of a former metalliferous mine-Enguilaes,Aveyron,France.Applied Geochem.,l8(3):395—408. Drouet,C.,Baron,D.,and Navrotsky,A.,2003.On the thermochemistry of the solid solution between iarosite and its chromate analog.Am.Minera1.,88,1949-1954. Dutrizac,J.E.,Hardy,D…J and Chen,T.T.,1996.The behaviour of cadmium during jarosite precipitation.Hydrometallurgy,41 (2—31:269-285. Lin,Z.X.,and Herbert,R.B.,1997.Heavy metal retention in secondary precipitates from a mine rock dump and underlying soil,DalalTla,Sweden.EnvironmentaZ Geology,33(1):1-12. Ma Shengfeng,2005.Experimental study on environmental properties of the process of deposiitng minerals of jraosite group.Graduation Thesis,Peking University(in Chinese with English abstract).25—28. Ma Shengfeng,Wang Changqiu,Lu Anhuai,Gut Yanjun and Yang Lei,2005.The ffeatment of high-concentrated sulfur wastewater by the process of iarosites deposiiton.Acta Petro1. Minera1.,24(6):547—550(in Chjnese with English abstract). Prieto,M.,Fernandez-Gonzalez,A.,and Martin-Diaz,R.,20o2. Sorption of chromate ions diffusing through barite-hydrogel composites:Implications for hte fate nad transport ofchromium in the environment.Geochim.Cosmochim.Acta,66(5): 783—l795. Sasaki,K.,and Konno,H.,2000.Morphology of jraosite-group compounds precipiatted from biologically and chemically oxidized Fe ions.Canadian Mineralogist.38(1 1:45—56. Wang Changqiu,Ma Shengfeng,Lu Anhuai and Zhou Jiangong, 2005.The formation condiitons of iraosite and its environmental signiifcance.Acta Petro1.Minera1.。24(6): 607 l1(in Chinese wiht English abstract). Zou Xuegong,1998.Theoretical anlysis of removing iron by jraosite.Metallurgical Collections,(6):l8—20(in Chinese). 

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