research article preparation and characteristics of...

Research ArticlePreparation and Characteristics of Polyaluminium Chloride byUtilizing Fluorine-Containing Waste Acidic Mother Liquid fromClay-Brine Synthetic Cryolite Process

Feng-shan Zhou1 Bo Hu12 Bao-lin Cui1 Feng-bao Liu13 Fang Liu1 Wei-heng Wang1

Yang Liu1 Rong-rong Lu1 Ying-Mo Hu1 Yi-he Zhang1 and Jin-Guang Wu4

1 School of Materials Science and Technology China University of Geosciences Beijing 100083 China2National Library of China Beijing 100081 China3 Tabei Exploratory amp Development Department of PetroChina Tarim Oilfield Company Korla 841000 China4College of Chemistry and Molecular Engineering Peking University Beijing 100871 China

Correspondence should be addressed to Feng-shan Zhou zhoufscugbeducn and Yi-he Zhang zyhcugbeducn

Received 28 May 2014 Accepted 29 July 2014 Published 17 August 2014

Academic Editor Chaomeng Dai

Copyright copy 2014 Feng-shan Zhou et alThis is an open access article distributed under theCreativeCommonsAttributionLicensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Clay-brine process employing activated clay NaCl HCl andHF as rawmaterials is the primarily advanced technology to synthesizecryolite in the present industrial grade However plenty of byproducts of fluorine-containing waste HCl at the concentration ofabout 10sim12 could not be utilized comprehensively and are even hazardous to the environmentThis work proposed a new two-step technology to prepare inorganic polymer flocculants polyaluminium chloride (PAC) from synthetic cryolite mother liquorMany specific factors such as the variety of aluminide source reaction temperature and time reagent ratio and manner of alkalineaddition were taken into consideration and their influences on the performances of produced PAC were discussed It was foundthat synthetic cryolite mother liquor could react with bauxite and calcium aluminate directly to prepare cheap PAC with plentyamount of water insoluble CaF

2and CaSiF

6produced as well However once HCl was introduced into synthetic cryolite mother

liquor as well as by utilizing bauxite as aluminide source and sodium aluminate as adjusting basicity agent the resultant PACwoulddissolve out higher amount of aluminum while producing little amount of water insoluble materials The coagulation behavior ofthe specially produced PAC could even match the industrial grade PAC conforming to national standard

1 Introduction

11 Cryolite and Clay-Brine Synthetic Process Cryolite withprofessional name sodium aluminum fluoride andmolecularformula Na

3AlF6 is a kind of white and small-geometry

crystal whose group can be divided into synthetic cryolite andnatural cryolite according to the origin of the material itselfIt is well recognized that synthetic cryolite possesses muchhigher solubility than natural cryolite The other propertyparameters of synthetic cryolite are as follows specific gravity3 hardness 2sim3 melting point 1000∘C and air-slaking afterabsorption of water Due to these distinguished propertiescryolite has been applied in diverse fields amongwhich beingutilized as fluxing agent is one of the most common waysBesides it is also the significant raw material of aluminium

industry For example about 100sim120 kg cryolitewas reportedto be consumed to produce 1 t metal-alumina in the presenttechnology [1] Thus it is concluded that the large-scalealuminium industry would never exist in this world withoutcryolite

There are various kinds of process routes to fabricatecryolite in industry and the raw materials differ greatly fromeach other accordingly Among all the technology routesthe most industrial competitive and representative one is thewell-known clay-brine process (CBP) employing activatedclay NaCl HCl andHF as rawmaterials [2]The famous Do-fluoride Chemicals Co Ltd located in Jiaozuo of China isthe biggest production corporation in the world to producesynthetic cryolite and the process route it adopts is also theCBP as shown in Figure 1

Hindawi Publishing CorporationJournal of ChemistryVolume 2014 Article ID 274126 7 pageshttpdxdoiorg1011552014274126

2 Journal of Chemistry

Activated clayhydrochloric acid

Reaction kettle Cryolitesuspension

Residue

CentrifugePressurefiltration Filtrate

Hydrofluoric acid CryoliteSodium chloride

Efflux of excess partCalcined bauxite Alkali

Inorganic polymer flocculants (IPFs)

Synthetic cryolite mother liquor by clay-brine process

Figure 1 Process chart of synthetic cryolite by clay-brine process

12 Features of Cryolite Mother Liquor Fluorine-containingwaste hydrochloric acid from CBP of synthetic cryolite isalso commonly known as synthetic cryolite mother liquor(SCML) According to the following CBP reaction principles[2] 6mol affiliated HCl will be produced to fabricate 1molcryolite with AlCl

3as the aluminide source The amount

would even increase to as high as 12mol once AlCl3is

replaced by Al2O3as the aluminide source Among the total

12molHCl 6molHCl would reverse back into the systemto leach the clay for cycling utilization However the other6molHCl would still remain as residue in the system andneed to let out for postprocessing enhancing the complexityas well as the cost of the process route remarkably It isestimated that 50 000m3a extra acidic synthetic cryolitemother liquor would be created if Do-fluoride Chemicals Cofabricates 20 000 ta synthetic cryolite [3ndash5] Consider

Al2O3+ 6HCl 997888rarr 2AlCl

3+ 3H2O (1)

AlCl3+ 6HF + 3NaCl 997888rarr Na

3AlF6+ 6HCl (2)

(2AlCl3+ 12HF + 6NaCl 997888rarr 2Na

3AlF6+ 12HCl) (3)

Though SCML from CBP of synthetic cryolite possessescomplicated composition as shown in Table 1 Fminus Clminus H+and Na+ are four main kinds of ions in it Meanwhile thetotal acidity ranges from 110 gL to 140 gL (or 3sim4molL)(or 104sim138) and the weight percentage of NaCl is nomore than 40 gL This is because the clay utilized in acidleaching is always made from the low grade calcined bauxitewith 119908(Al

2O3) ge 25 and 119908(Fe

2O3) ge 20

According to the standard of public water establishedby the American Environmental Protection Administration(EPA) drinking water with 04sim06mgL Fminus will do benefitto human health However the situation is not that optimisticwhen drinking water with Fminus concentration higher than10mgL for a long time which may even cause seriousdiseases such as dental and bone fluorosis [4] In additionboth the difficult controlling of technology and the expensivecost of waste outlet during the treatment process of SCMLas acidic waste make corporations suffer from tremendous

Table 1 Chemical composition of synthetic cryolite mother liquor(SCML)

Anionic ion Concentration(gL) Cationic ion Concentration

(gL)Fminus 1810000 Na+ 2428000Clminus 13971000 K+ 028402CO3

2minus 2000000 Ca2+ 007636SO4

2minus 075030 Mg2+ 009012SiO3

2minus (SiO2) 001120 Fe3+ 308000Al3+ 000000

environmental protection pressure [5] And the enterprisehas a great amount of waste acid liquid containing Fminuswhich is badly in need of finding an environmental economyprocessing method Meanwhile it is difficult to polymerizein the preparation of PAC because of the common ion effectof Fminus We need to search for a new preparation methodin this paper Thus this work optimized the process routeusing SCML to produce inorganic polymer flocculants (IPFs)polyaluminium chloride (PAC) Moreover the reason forthe generation of highly water insoluble materials was wellexplained via exploration of the XRD phase of products fromthe reactions Besides the well cost performance productPAC was obtained and the optimized route had also beenapplied in industry

2 Materials and Experimental Methods

21 Materials and Instruments Sodium aluminate HClHAc NaAc Zn(Ac)

2 NH3sdotH2OKF and EDTAwere used for

chemical purity Other purchased industrial grade raw mate-rials included technical hydrochloric acid diluted to 18wtbauxite (Al

2O330wt) calcined bauxite (Al

2O340wt)

calcium aluminate powder (Al2O353wt CaO 28wt)

polyaluminium chloride (PAC Al2O329wt) SCML was

the byproduct acid from Do-fluoride Chemicals Co and thecomposition was described in Table 1

Journal of Chemistry 3

pH values were determined by pH500 meter CLEANUSA SGZ-2 turbidimeter was employed tomeasure turbidityby Shanghai Yuefeng Instruments amp Meters Co Ltd CODCr(potassium dichromate as oxidant) was measured by 5B-6COD reactor Lian-Hua Tech Co China

22 Experimental Methods and Details

221 Preparation of PAC from Synthetic Cryolite MotherLiquor Certain amount of synthetic cryolite mother liquorwas added into a three-neck flask with a condenser firstlyAfter the temperature of the flask was heated to 70∘C in oilbath certain amount of bauxite was added into the systemstep by step The reaction should continue for 1 h after thetemperature increases to 100∘CThen alkaline polymerizationadjusting agent (APA calcium aluminate powder or sodiumaluminate powder) was added into the above reaction systemgradually to adjust pH value The addition speed of APAdepended on pH value of the system when pH value waslower than 27 the speed can be fast but when it was over 27the speed should be slow until it increased to 35sim38 furtherAt this point APA should not be added into the systemany more After all these operations the reaction is kept foranother 15 h at 100∘CThen the reaction should be suspendedimmediately via halting both the vigorous stirring and oilbath heating followed by coagulating the system for 12 h usingthe residual heat of oil bath Liquid PAC was obtained afterthe filtering of the upper clear liquid of the already stewedreaction suspension And solid PACwas finally obtained afterthe initial liquid PAC was dried at 105∘C

222 Basicity of the Produced PAC OHminus is the basic compo-nent influencing the morphology of polyaluminium chloride[6ndash9] whose index in PAC is measured by basicity (B)According to GB 15892-2003 (water treatment chemical-polyaluminium chloride) [10] basicity can be measured Themol percentage of OH and Al in PAC is defined as basicityand this parameter can reflect the degree of polymerizationof PAC to some extent which affects the coagulation perfor-mances of PAC Basicity can be calculated according to thefollowing during the fabrication process of PAC

Basicity = (OH)(Al)times 100 (4)

223 Coagulation Performance of the Produced PAC Coag-ulation tests were performed by using simulated diatomitewater and real oily wastewater samples All coagulation testswere conducted in 100mL beakers using a magnetic stirringapparatus 100mL of the test water was placed in a beaker andstirred rapidly at 200 rpm for 2min after adding the coagulantat room temperature followed by slow stirring at 40 rpmfor 2min and sedimentation for 10min Then a supernatantsample was taken at 10 cm below the surface of the test waterfor turbidity and CODCr measurement

224 Characterization of the Produced PAC The producedPAC solution was dehydrated at 105∘C and made powder

sample for structure analysis X-ray diffraction (XRD) wasmeasured for the determination of crystalline phases in solidcoagulants using Dmax-rA X-ray diffractometer with Cu Kradiation in the 2120579 range of 3∘ to 80∘ at a scan rate of 8∘minThe solid produced PAC was analyzed by FT-IR with thePerkin Elmer spectrum 100 FT-IR spectrophotometer andpotassium bromide pellet methodThe spectra were scannedin the range of 4000 to 500 cmminus1

3 Results and Discussion

31 Synthesis Optimization The pH value of the leachingreaction systemwas themost critical technological parameterduring the fabrication process of PAC [11ndash13] Due to theamphoteric compound property of aluminum the state ofaluminum salt solution showed certain transformation lawalong with pH value alteration When the pH value of theleaching agent was less than 4 aluminum mostly existedas hydrated ions These hydrated ions would get hydrolysedas pH value increased and the mononuclear or monohy-droxy compounds would first generate and then the newproduced compounds evolve into three-nuclear or multi-hydroxy compounds along with further increase of pH valueIn this compound bridging effect took place between ionsand hydroxyl creating multiple nuclear hydroxyl complexesknown as inorganic polymerThe specific states of aluminumsalt solution along with pH value alteration were as follows[13ndash15]

pH lt 4 [Al(H2O)119899]3+ n = 6sim10

4 lt pH lt 6 [Al6(OH)1

5]

3+ [Al7(OH)1

7]

4+[Al8(OH)20]

4+ [Al13(OH)34]

5+6 lt pH lt 8 [Al(OH)

3]

pH gt 8 [Al(OH)4]

minus [Al8(OH)26]

2minus

The chemical equations to prepare PAC were indicated asfollows


3+ 3H2O (5)

AlCl3+NaAl(OH)

4997888rarr [Al

2(OH)119899Cl6minus119899]

119898+NaCl (6)

According to the above reaction principles the influenc-ing factors such as the kind and amount of APA amountof water insoluble material and leaching aluminum as wellas the degree of polymerization (or basicity) were deeplydiscussed in this work and results were described in Table 2from which two laws were concluded

(1) Once synthetic cryolite mother liquor was the onlytaken acid leaching agent the leaching efficiency ofaluminum was not that high Nevertheless it couldbe enhanced apparently when appropriate HCl wasadded into synthetic cryolite mother liquor

(2) When calcium aluminate was used as APA Ca2+would react with Fminus and SiO

3

2minus in synthetic cryolitemother liquor and high amount of water insolublematerial was thus produced However if calcium alu-minate was replaced by sodium aluminate as APA the


Table 2 Optimization experiment to prepare PAC by SCML leaching bauxite

Sample Acid Alkali Al2O3 () Basicity () Insoluble solid in water ()A SCML Calcium aluminate 287 87 112B SCML + HCl Calcium aluminate 291 79 58C SCML + HCl Sodium aluminate 302 66 15

10 20 30 40 50 60 70

0

500

1000

1500

2000

2 2 221 1 1

3 3 1

Inte

nsity

2120579

(1) CaSiF6

(2) CaF2

(3) AlCl3

Figure 2 XRD spectra of PAC (Sample B) generated from polymer-ization induced by calcium aluminate as pH adjusting agent

amount of water insoluble material would decreasesignificantly

Based on the above experimental results the reactioncondition was optimized as follows 200mL mixed acidwas obtained first by blending 150mL synthetic cryolitemother liquor (containing HCl 12) with 50mL industrial31 concentrated HCl 80 g bauxite was then added into themix and the reaction was kept for 1sim2 h at 80sim100∘C Thepolymerization was completed when 23 g sodium aluminatewas added into the system to adjust pH value followed bycoagulation for 12 h under vigorous stirring PACwith indus-trial quality standard could be obtained after the stewing andfiltering of the reaction agent

32 Structure of the Produced PAC The final product follow-ing the optimized preparative conditions was analyzed withXRD and FT-IR to obtain detailed structural information

XRD spectra of PAC (Sample B) generated from poly-merization induced by calcium aluminate as pH adjustingagent were showed in Figure 2 It was indicated that thereappeared characteristic absorption bands assigned to waterinsoluble CaF

2and CaSiF

6besides the absorption band of

AlCl3 This might be because HF in synthetic cryolite mother

liquor dissolved SiO2in calcium aluminate into SiO

3

2minus andboth SiO

3

2minus and Fminus encountered Ca2+ leached from calciumaluminate to form water insoluble CaF

2and CaSiF

6

However in the XRD spectra of PAC (Sample C) gen-erated from polymerization induced by sodium aluminateas pH adjusting agent (Figure 3) it was not difficult to findthat there existed characteristic absorption bands of Fe exceptfor the absorption band of AlCl

3 This might be because HF

0 10 20 30 40 50 60 70 80

0

500

1000

1500

2000

2500

AlIn

tens

ityFe

2120579

Figure 3 XRD spectra of PAC (Sample C) generated from polymer-ization induced by sodium aluminate as pH adjusting agent

10 20 30 40 50 60 700

500

1000

1500

2000

Inte

nsity

(cps

)

and

and

and

and

and

lowast

lowast

lowast lowast

2120579 (deg)

lowast SiF4 AlCl3middot6H2Oand Na2Al22O34

Figure 4 XRD spectra of crystal leached from bauxite via SCMLand HCl mixed acid

and HCl in synthetic cryolite mother liquor dissolved Fe inbauxite into Fe2+ and Fe3+ with Fe(OH)

3further produced

In order to confirm that Fe in bauxite can be abundantlydissolved out in acid leaching process SCML and HCl mixedacid was proposed to leach bauxite XRD results of thecrystal obtained from the dried leaching solution indicatedthat the main components of this crystal contained SiF

4

AlCl3sdot6H2O and Na

2Al22O34

(Figure 4) Thus it was clearthat PAC prepared from SCML was rather different fromindustrial grade PAC Instead it was made up of multiplecrystal phases and components and AlCl

3 FeCl

3 SiF4 and

H2SiO3were especially typical The plural gel formed by the

polymerization of these components might show synergismeffect on the coagulation characteristic of PAC [16ndash20]


4000 3500 3000 2500 2000 1500 1000 50010

20

30

40

50

60

70

80

Tran

smitt

ance

()

3390

1628640

778

1098

Wavenumber (cmminus1)

(a)

4000 3500 3000 2500 2000 1500 1000 500

10

20

30

40

50

60

70

Tran

smitt

ance

()

3430

1636

578

980

770

1090


(b)

Figure 5 FT-IR spectra for (a) the produced PAC by SCML and (b) industrial grade PAC

It was well recognized in collochemistry that the positivedischarged Fe(OH)

3colloidal particles with small amount in

system could create bridged bonds among negative colloidalparticles just like coagulating agent thus getting precipitatedviamutual absorptionOn this occasion Fe(OH)

3functioned

as coagulant aid [18 19]The existence of small amount of silica sol (also ludox)

not only could promote the coagulating process of water aswell as improving the structure of precipitation particles butalso could increase their weight accelerating the formationand precipitation of precipitation particles Therefore silicasol could also function as coagulant aid Unlike the largeamount of positive charge of Al

13as key component of

flocculation agent of PAC the surface of silica gel particleswas filled with negative charge instead Thus these twokinds of particles with totally opposite charge would allureeach other to get absorbed Meanwhile silica gel could alsoabsorb other scattered colloidal particles with positive chargestrengthening the coagulating effect accordingly [15 17 2122]

From the above discussion it was found that the pro-duced PAC by SCML (PAC-SCML) was rather different fromcommon industrial grade PAC (PAC-IG) Except for the rel-ative strong coagulating character it was a kind of compositeflocculant containing certain amount of Fe and Si whichcould be treated as the compound of PAC polyaluminumferric chloride (PAFC) and polysilicate (PSi) [18ndash20 23]Besides FT-IR spectra of this special PAC showed muchdifference from that of common PAC as indicated in Figure 5

The possible chemical bonds in PAC-SCML (Sample C)were investigated by the FT-IR spectra and were comparedwith PAC-IG (Figure 5)The two samples showed similar FT-IR spectra Both spectra exhibited a broad absorption peakin the range of 3200ndash3650 cmminus1 (3390 cmminus1 for PAC-SCMLand 3430 cmminus1 for PAC-IG) which could be assigned to thestretching vibrations of ndashOH groups The peaks in the rangeof 1600ndash1700 cmminus1 (1628 cmminus1 for PAC-SCML and 1636 cmminus1PAC-IG) were attributed to the bending vibrations of water

absorbed polymerized and crystallized in the coagulantThe PAC-IG was not a pure substance which also containssome iron ions The peak at 1098 cmminus1 for PAC-SCML andthe peak at 1090 cmminus1 for PAC-IG were attributed to theasymmetric stretching vibration of FendashOHndashFe or AlndashOHndashAlfurthermore there were two peaks at 778 cmminus1 and 640 cmminus1for PAC-SCML and two peaks at 770 cmminus1 and 578 cmminus1 forPAC-IG which were attributed to bending vibrations of FendashOH and AlndashOH respectively [24ndash28]

33 Coagulation Characteristics Coagulation tests were per-formed by using simulated diatomite water and real oilywastewater samples The turbidity of the simulated diatomitewater samples was 1480NTU 720NTU and 80NTU TheCODCr of the oily wastewater samples obtained from LiaohePetroleum Exploration Bureau of China was 534mgL and itsturbidity was 124NTU

As indicated in the flocculation results in Table 3 thecoagulation effect of PAC-IG was much better than thatof PAC-SCML for simulated diatomite water with low tur-bidity However the coagulation effect of PAC-SCML haddistinguished advantages over that of PAC-IG for simulateddiatomite water with high turbidity which might originatefrom the formation of PAFC and PSi with strengtheningcoagulation effect in acid leaching process Moreover thesmall amount of water insoluble CaF

2and CaSiF

6in PAC-

SCML could also benefit the coagulating reaction for highturbidity water

The CODCr removal of PAC-SCML and PAC-IG bothachieved the minimum at 60mgL dosage while PAC-SCMLwas relatively superior to PAC-IG for oily sewage fromLiaohe Oilfield and the same law was presented for turbidityremoval

The results suggested that despite the small differencein alumina content between PAC-SCML and PAC-IG PAC-SCML was superior to PAC-IG in both the comprehensivecoagulating character and manufacturing cost due to thecertain amount of Fe and Si in PAC-SCML


Table 3 Coagulation behavior contrast of the produced PAC by SCML versus industrial grade PAC

Performances Simulated diatomite water added 30mgL flocculant Oily wastewater added 60mgL flocculant

Residual turbidity (NTU) Residual CODCr(mgL)

Residual turbidity(NTU)

Samples 1480 Initial 720 Initial 80 Initial 534 Initial 124 InitialA 261 mdash mdash 358 42B 279 mdash mdash 355 38C 25 24 15 245 6PAC-IG 34 20 10 330 18

4 Conclusions

The preparation of PAC coagulant from synthetic cryolitemother liquor from clay-brine process (PAC-SCML) withadvanced performances compared with conventional indus-trial grade PAC (PAC-IG) coagulant was achieved Reactionconditions including the choice of leaching acid and alkalinepolymerization adjusting agent the pH value and the reac-tion temperature and reaction time were thoroughly studiedto optimize the coagulation performances and minimize theinsoluble solid in water of the prepared coagulant The opti-mized technique to prepare PAC-SCML was that adjustingthe concentration of HCl in synthetic cryolite mother liquorto 18 with the industrial grade HCl (the concentrationabout 32 to 36 in general) firstly and then adding theneeded bauxite Then the acid leaching reaction was kept for1sim2 h at 80sim100∘C and sodium aluminate was consequentlyadded to adjust pH value to 35sim38 The whole technologywould be completed after a 24 h coagulation process Thecoagulation performances tested showed that PAC-SCML isbetter than PAC-IG in turbidity removal at high turbiditysimulated diatomite water and in CODCr removal at real oilywastewater BothXRDand FT-IR results confirmed that thereexisted certain amount of Fe and Si in PAC-SCML whichcould combine Al to form multiple nuclear inorganic poly-mer and make the resultant PAC-SCML possess advancedcoagulating performances This technology will become aneffective way to treat the large amount of waste acid solutionin cryolite fabrication process

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This research was supported by the National High Tech-nology Research and Development Program (863 Program2012AA06A109) of China

References

[1] H P Ding ldquoProduction technology and market situation ofcryolite productsrdquo Yunnan Metallurgy vol 33 no 3 pp 64ndash692004

[2] Z Y Tang ldquoProducing sand like synthetic cryolite by claybittern methodrdquo Patent CN 1056091 A 1991

[3] H H Yu H Wang S Y Yang et al ldquoThe comprehensiveutilization of aluminium fluoride mother liquorrdquo InorganicChemicals Industry vol 37 no 4 pp 34ndash35 2005

[4] T Dong J M Liu Z X Li et al ldquoHigh concentration fluoridewastewater treatmentrdquo Tianjin Chemical Industry vol 18 no 5pp 58ndash60 2004

[5] M Zhang H N Yang X X Zhang et al ldquoPreparation of polya-luminium ferrous chloride by using cryolite mother liquorrdquoInorganic Chemicals Industry vol 42 no 3 pp 43ndash44 2010

[6] L Allouche and F Taulelle ldquoConversion of Al13Keggin 120576 into

Al30 a reaction controlled by aluminum monomersrdquo Inorganic

Chemistry Communications vol 6 no 9 pp 1167ndash1170 2003[7] W Seichter H J Mogel P Brand and D Salah ldquoCrystal

structure and formation of the aluminium hydroxide chlorideAl-13(OH)(24)(H2O)(24) Cl-15 center dot 13H(2)Ordquo EuropeanJournal of Inorganic Chemistry no 6 pp 795ndash797 1998

[8] W Z Wang and P H Hsu ldquoThe nature of polynuclear OH-Alcomplexes in laboratory-hydrolyzed and commercial hydrox-yaluminum solutionsrdquo Clays amp Clay Minerals vol 42 no 3 pp356ndash368 1994

[9] J E van Benschoten and J K Edzwald ldquoChemical aspects ofcoagulation using aluminum saltsmdashI Hydrolytic reactions ofalum and polyaluminum chloriderdquoWater Research vol 24 no12 pp 1519ndash1526 1990

[10] GB15892-2003 ldquoWater treatment chemical-Poly aluminiumchlorid Chinese administration of quality supervision inspec-tion and quarantinerdquo

[11] R R Lu Y H Zhang F S Zhou XWang Q An and Z MengldquoNovel polyaluminum ferric chloride composite coagulantfrom Bayer red mud for wastewater treatmentrdquo Desalinationand Water Treatment vol 295 pp 1ndash9 2013

[12] W Li T Hua and Q X Zhou ldquoPreparation morphology andcoagulation characteristics of a new polyferric chloride coagu-lant prepared using pyrite cindersrdquo Environmental Technologyvol 32 no 8 pp 911ndash920 2011

[13] Z L Huang Y H Hu and Z F Jiang ldquoPreparation ofpolyaluminum chloride from waste chlorhydric acid and poorquality Kaolinrdquo Environmental Protection of Chemical Industryvol 22 no 5 pp 284ndash286 2002

[14] W Lan H Qiu J Zhang et al ldquoCharacteristic of a novelcomposite inorganic polymer coagulant-PFAC prepared byhydrochloric pickle liquorrdquo Journal of HazardousMaterials vol162 no 1 pp 174ndash179 2009

[15] T Sun C Sun G Zhu et al ldquoPreparation and coagulationperformance of poly-ferric-aluminum-silicate-sulfate from flyashrdquo Desalination vol 268 no 1ndash3 pp 270ndash275 2011


[16] G Zhu H ZhengW ChenW Fan P Zhang and T TshukuduldquoPreparation of a composite coagulant polymeric aluminumferric sulfate (PAFS) for wastewater treatmentrdquo Desalinationvol 285 no 31 pp 315ndash323 2012

[17] B Y Gao Z S Wang and H X Tang ldquoStudy on thehydrolysis-polymerization process of aluminum and the inter-action between hydrolyzed aluminum species and polysilicicacid in flocculant polyaluminum silicate chloride (PASC)rdquoACTA Scientiae Circumstantiae vol 20 no 2 pp 151ndash153 2000

[18] F S Zhou L Ma J G Wu et al ldquoComplexing agent preparingmethod and use thereofrdquo CN1552629 2004

[19] F S Zhou L Ma J G Wu et al ldquoComplexometric synergistpreparing method and use thereofrdquo CN1552636 2004

[20] F S Zhou L Ma J G Wu et al Flocculent preparing methodand use thereof CN1552637 2004

[21] D S Wang and H X Tang ldquoPoly ferric silicon type compoundinorganic high molecular flocculant and its preparing methodrdquoCN1210818 1999

[22] Z P Ai B Y Gao and S R Wang ldquoElectron microscopicobservation on sol and gel of polysilicic acidrdquo EnvironmentalChemistry vol 13 no 2 pp 119ndash122 1994

[23] Y M Fang X D Zhao and X L Zhang ldquoStudy on the imagestructure and coagulation behavior of polysilicate-aluminumferricrdquo Industrial Safety and Environmental Protection vol 33no 10 pp 22ndash24 2007

[24] F Zhou S Wang J Su et al ldquoStructural characteristicsof infrared spectra for polyaluminum chloride in enhancedreactions of modificationrdquo Spectroscopy and Spectral Analysisvol 24 no 5 pp 532ndash535 2004

[25] H Yu B Y Gao Q Y Yue et al ldquoStudy on the structuralcharacteristics of polyaluminum silicata chloride by infraedspectrum methodrdquo Journal of Shandong University (NaturalScience Edition) vol 34 no 2 pp 198ndash201 1999

[26] W N Chen H P Zhong J Yang et al ldquoAnalysis of IRspectrum and crystalmorphology of polyalumina-silica chlorid(PASC) prepared by various methodrdquo Chemical Research andApplication vol 14 no 1 pp 73ndash75 2002

[27] F S Zhou S H Wang J Z Su et al ldquoInfrared spectraand characteristics of PMCmdasha multicore inorganic polymerflocculantrdquo Fine Chemicals vol 20 no 10 pp 615ndash618 2003

[28] X Zhang L Zhou and M Tang ldquoStudy of infrared spectraof polyaluminum ferric chloriderdquo Spectroscopy and SpectralAnalysis vol 22 no 1 pp 39ndash42 2002

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CatalystsJournal of


Activated clayhydrochloric acid

Reaction kettle Cryolitesuspension

Residue

CentrifugePressurefiltration Filtrate

Hydrofluoric acid CryoliteSodium chloride

Efflux of excess partCalcined bauxite Alkali

Inorganic polymer flocculants (IPFs)

Synthetic cryolite mother liquor by clay-brine process

Figure 1 Process chart of synthetic cryolite by clay-brine process

12 Features of Cryolite Mother Liquor Fluorine-containingwaste hydrochloric acid from CBP of synthetic cryolite isalso commonly known as synthetic cryolite mother liquor(SCML) According to the following CBP reaction principles[2] 6mol affiliated HCl will be produced to fabricate 1molcryolite with AlCl

3as the aluminide source The amount

would even increase to as high as 12mol once AlCl3is

replaced by Al2O3as the aluminide source Among the total

12molHCl 6molHCl would reverse back into the systemto leach the clay for cycling utilization However the other6molHCl would still remain as residue in the system andneed to let out for postprocessing enhancing the complexityas well as the cost of the process route remarkably It isestimated that 50 000m3a extra acidic synthetic cryolitemother liquor would be created if Do-fluoride Chemicals Cofabricates 20 000 ta synthetic cryolite [3ndash5] Consider


3+ 3H2O (1)

AlCl3+ 6HF + 3NaCl 997888rarr Na

3AlF6+ 6HCl (2)

(2AlCl3+ 12HF + 6NaCl 997888rarr 2Na

3AlF6+ 12HCl) (3)

Though SCML from CBP of synthetic cryolite possessescomplicated composition as shown in Table 1 Fminus Clminus H+and Na+ are four main kinds of ions in it Meanwhile thetotal acidity ranges from 110 gL to 140 gL (or 3sim4molL)(or 104sim138) and the weight percentage of NaCl is nomore than 40 gL This is because the clay utilized in acidleaching is always made from the low grade calcined bauxitewith 119908(Al

2O3) ge 25 and 119908(Fe

2O3) ge 20

According to the standard of public water establishedby the American Environmental Protection Administration(EPA) drinking water with 04sim06mgL Fminus will do benefitto human health However the situation is not that optimisticwhen drinking water with Fminus concentration higher than10mgL for a long time which may even cause seriousdiseases such as dental and bone fluorosis [4] In additionboth the difficult controlling of technology and the expensivecost of waste outlet during the treatment process of SCMLas acidic waste make corporations suffer from tremendous

Table 1 Chemical composition of synthetic cryolite mother liquor(SCML)

Anionic ion Concentration(gL) Cationic ion Concentration

(gL)Fminus 1810000 Na+ 2428000Clminus 13971000 K+ 028402CO3

2minus 2000000 Ca2+ 007636SO4

2minus 075030 Mg2+ 009012SiO3

2minus (SiO2) 001120 Fe3+ 308000Al3+ 000000

environmental protection pressure [5] And the enterprisehas a great amount of waste acid liquid containing Fminuswhich is badly in need of finding an environmental economyprocessing method Meanwhile it is difficult to polymerizein the preparation of PAC because of the common ion effectof Fminus We need to search for a new preparation methodin this paper Thus this work optimized the process routeusing SCML to produce inorganic polymer flocculants (IPFs)polyaluminium chloride (PAC) Moreover the reason forthe generation of highly water insoluble materials was wellexplained via exploration of the XRD phase of products fromthe reactions Besides the well cost performance productPAC was obtained and the optimized route had also beenapplied in industry

2 Materials and Experimental Methods

21 Materials and Instruments Sodium aluminate HClHAc NaAc Zn(Ac)

2 NH3sdotH2OKF and EDTAwere used for

chemical purity Other purchased industrial grade raw mate-rials included technical hydrochloric acid diluted to 18wtbauxite (Al

2O330wt) calcined bauxite (Al

2O340wt)

calcium aluminate powder (Al2O353wt CaO 28wt)

polyaluminium chloride (PAC Al2O329wt) SCML was

the byproduct acid from Do-fluoride Chemicals Co and thecomposition was described in Table 1












pH lt 4 [Al(H2O)119899]3+ n = 6sim10


5]

3+ [Al7(OH)1

7]

4+[Al8(OH)20]

4+ [Al13(OH)34]


3]

pH gt 8 [Al(OH)4]

minus [Al8(OH)26]

2minus



3+ 3H2O (5)

AlCl3+NaAl(OH)

4997888rarr [Al

2(OH)119899Cl6minus119899]

119898+NaCl (6)




3





10 20 30 40 50 60 70

0

500

1000

1500

2000

2 2 221 1 1

3 3 1

Inte

nsity

2120579

(1) CaSiF6

(2) CaF2

(3) AlCl3






2and CaSiF




3

2minus andboth SiO

3


2and CaSiF

6



0 10 20 30 40 50 60 70 80

0

500

1000

1500

2000

2500

AlIn

tens

ityFe

2120579


10 20 30 40 50 60 700

500

1000

1500

2000

Inte

nsity

(cps

)

and

and

and

and

and

lowast

lowast

lowast lowast

2120579 (deg)




3further produced


4


2Al22O34


3 FeCl

3 SiF4 and




4000 3500 3000 2500 2000 1500 1000 50010

20

30

40

50

60

70

80

Tran

smitt

ance

()

3390

1628640

778

1098


(a)

4000 3500 3000 2500 2000 1500 1000 500

10

20

30

40

50

60

70

Tran

smitt

ance

()

3430

1636

578

980

770

1090


(b)





3functioned










2and CaSiF

6in PAC-










4 Conclusions




Acknowledgment


References









































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of












pH lt 4 [Al(H2O)119899]3+ n = 6sim10


5]

3+ [Al7(OH)1

7]

4+[Al8(OH)20]

4+ [Al13(OH)34]


3]

pH gt 8 [Al(OH)4]

minus [Al8(OH)26]

2minus



3+ 3H2O (5)

AlCl3+NaAl(OH)

4997888rarr [Al

2(OH)119899Cl6minus119899]

119898+NaCl (6)




3





10 20 30 40 50 60 70

0

500

1000

1500

2000

2 2 221 1 1

3 3 1

Inte

nsity

2120579

(1) CaSiF6

(2) CaF2

(3) AlCl3






2and CaSiF




3

2minus andboth SiO

3


2and CaSiF

6



0 10 20 30 40 50 60 70 80

0

500

1000

1500

2000

2500

AlIn

tens

ityFe

2120579


10 20 30 40 50 60 700

500

1000

1500

2000

Inte

nsity

(cps

)

and

and

and

and

and

lowast

lowast

lowast lowast

2120579 (deg)




3further produced


4


2Al22O34


3 FeCl

3 SiF4 and




4000 3500 3000 2500 2000 1500 1000 50010

20

30

40

50

60

70

80

Tran

smitt

ance

()

3390

1628640

778

1098


(a)

4000 3500 3000 2500 2000 1500 1000 500

10

20

30

40

50

60

70

Tran

smitt

ance

()

3430

1636

578

980

770

1090


(b)





3functioned










2and CaSiF

6in PAC-










4 Conclusions




Acknowledgment


References









































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




10 20 30 40 50 60 70

0

500

1000

1500

2000

2 2 221 1 1

3 3 1

Inte

nsity

2120579

(1) CaSiF6

(2) CaF2

(3) AlCl3






2and CaSiF




3

2minus andboth SiO

3


2and CaSiF

6



0 10 20 30 40 50 60 70 80

0

500

1000

1500

2000

2500

AlIn

tens

ityFe

2120579


10 20 30 40 50 60 700

500

1000

1500

2000

Inte

nsity

(cps

)

and

and

and

and

and

lowast

lowast

lowast lowast

2120579 (deg)




3further produced


4


2Al22O34


3 FeCl

3 SiF4 and




4000 3500 3000 2500 2000 1500 1000 50010

20

30

40

50

60

70

80

Tran

smitt

ance

()

3390

1628640

778

1098


(a)

4000 3500 3000 2500 2000 1500 1000 500

10

20

30

40

50

60

70

Tran

smitt

ance

()

3430

1636

578

980

770

1090


(b)





3functioned










2and CaSiF

6in PAC-










4 Conclusions




Acknowledgment


References









































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


4000 3500 3000 2500 2000 1500 1000 50010

20

30

40

50

60

70

80

Tran

smitt

ance

()

3390

1628640

778

1098


(a)

4000 3500 3000 2500 2000 1500 1000 500

10

20

30

40

50

60

70

Tran

smitt

ance

()

3430

1636

578

980

770

1090


(b)





3functioned










2and CaSiF

6in PAC-










4 Conclusions




Acknowledgment


References









































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of







4 Conclusions




Acknowledgment


References









































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of
























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

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