The Comparison of Red Mud Modification by Acid and Heat for Phosphate Removal from Aqueous Solution

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1 Inrnaional Journal of Innovaiv Sudis in Scincs and Enginring Tchnology ISSN (Onlin) Volum: 2 Issu: 12 Dcmbr 2016 Th Comparison of Rd Mud Modificaion by Acid and Ha for Phospha Rmoval from Aquous Soluion Vu Duy Linh 1, Tran Dac Chi 1, Huynh Trung Hai 1 1 School of Environmnal Scinc and Tchnology, Hanoi Univrsiy of Scinc and chnology No1, Dai Co Vi road, Hai Ba Trung disric, Ha Noi ciy, Vinam Absrac: This papr highlighs h rsul obaind from rd mud modificaion by chmical and ha mhods. Ths rsuls poind ha a h sam condiions of ph 7.0, modifid rd mud dos 10g/L, conac im 4 hours, shaking spd a 150rpm in h bach way. Th phospha adsorpion capaciy of rd mud modifid by ha a 400 o C wihin 1 hour was found o b ovr 82%, highr hr and wic ims compard o raw rd mud and rd mud modifid by 1.5M HCl soluion a 80 o C in 2 hours. Th rsuls also poind ha h isohrm and kinic of phospha adsorpion ono h surfac of boh modifid rd mud wr bs dscribd by Frundlich and Psudo scond ordr wih h corrlaion cofficin R 2 >0.99. Bsids, ha modificaion is also considrd as a lowr cos and nvironmnally frindly mhod han h ohr mhods such as acid or ha-acid modificaion du o wihou gnraing was soluion and acid gass. Kywords: Rd mud modificaion, phospha rmoval, ha modificaion of rd mud. 1. INTRODUCTION Vinam is considrd as on of h richs bauxi or rsourc counris in h world, h oal of bauxi or capaciy simad abou 5.5 billion ons and concnras mosly in h Cnral Highland (91.4%). In Dak Nong and Lam Dong provincs, h oal of bauxi or is invsigad o 4.3 billion ons [1]. A h momn, h biggs alumina plans in Vinam ar Nhan Co alumina (Dak Nong provinc) and Tan Rai alumina (Lam Dong provinc) mi approximaly 1.2 million ons of dry rd mud annually. According o h mass balanc, h producion of wo ons of alumina cras from 2 o 4 ons of rd mud or bauxi rsidu. Thrfor, in h nx 50 yars, abou 1.15 billion ons of rd mud will b gnrad from alumina producion in h Cnral Highland. In h Bayr procss, rd mud is known formally as bauxi rsidu and considrd a harmful facor o nvironmn du o h chmical composiion of rd mud. I found ha rd mud conains various oxids such as F 2 O 3, Al 2 O 3, SiO 2, TiO 2, Na 2 O, CaO, SO 3, P 2 O 5, Cr 2 O 3, c (h prcnag of F 2 O 3 and Al 2 O 3 ar simad abou 78.5%). Howvr, h rsarch conducd rcnly hav showd ha rd mud can b usd o rmov conaminans in an aquous soluion such as Zn 2+ [2], PO 4 3- [3], Pb 2+ [4], Cd 2+ [5], Co 2+ [6], As 5+ [7]., c. Wih h larg amoun of rd mud gnrad abov, h us of his was o rmov h conaminans in waswar in gnral, phospha in paricular can b sn as h ffciv soluion for nvironmnal procion in Vinam. Howvr, h chmical composiions of rd mud is srongly dpndns on h characrisics of prcursor bauxi or, as wll as on applid chnological procss, and consqunly flucuas srongly among sampls gnrad in h diffrn pars of h world. Thrfor, h rsuls rpord prviously could no b applid for rd mud in Vinam. Thus, i nds o b conducd h dail rsarch on h rd mud modificaion bfor using his marial for rmoving of phospha from an aquous soluion. Tabl 1: Chmical composiions of rd mud Naions Elmns (%W) Vinam [1] China [8] Turky [9] Iraq [10] SiO F2O Al2O Al(OH) TiO CaTiSiO CaO MgO FO(OH) γ-fo(oh) K2O Na2O A h momn, chmical and ha ar h mos popular mhods for rd mud modificaion du o hs mhods improv h adsorpion capaciy of rd mud 2016, IJISSET Pag 76

2 Inrnaional Journal of Innovaiv Sudis in Scincs and Enginring Tchnology ISSN (Onlin) Volum: 2 Issu: 12 Dcmbr 2016 for conaminans rmoval compard o raw rd mud. This sudy no only concnrad in h valuaion h ffc of hs mhods for rd mud modificaion for phospha rmoval from an aquous soluion, bu also compard h modificaion cos bwn chmical and ha mhods o find ou which mhod is rally advanag. 2. CHEMICALS AND METHODS 1. Rd mud Rd mud was collcd from Tan Rai Alumina Company, is locad in Lam Dong provinc, Cnral Highland of Vinam. Th ph and surfac ara of rd mud wr masurd o b 12.8 and 86 m 2 /g, rspcivly. 92.3% paricl sizs of rd mud lss han 600 µm. XRD analysis dcd ha rd mud conains h following minral componns: FO(OH) (50.8% W), F 2 O 3 (15.9% W), Al(OH) 3 (13.6% W), CaTiSiO 5 (9.0% W), CaCO 3 (4.9% W), γ-fo(oh) (3.8% W), and SiO 2 (2% W). Afr ph nuralizaion by dionizd war, rd mud was modifid by ha a 400 o C wihin 1 hour by using Lnon furnac (1.9KW). Bsids, rd mud was also modifid wih 1.5M HCl soluion a 80 o C in 2 hours. Afr modificaion, 400 o C modifid rd mud was usd dircly for phospha adsorpion, 1.5M HCl modifid rd mud was coninu washd and nuralizd by dionizd war and drid a 105 o C. 2. Chmicals All chmicals usd in his sudy (HCl, HNO 3, NaOH, KH 2 PO 4 ) wr of analyical grad and producd by Mrck (Grmany). Th phospha working soluion wih h concnraion rang of mg/l was prpard from KH 2 PO 4 sal and dilud by dionizd war. Th iniial ph of phospha soluion was adjusd by using NaOH and HNO 3 soluions 3. Exprimnal procdur Th phospha adsorpion xprimns wr conducd by bach chniqu a h room mpraur. A fixd amoun of h modifid rd mud (xcp h adsorbn dos xprimns) was addd ino a sris of h 100 ml flask conaining 25 ml of phospha soluion wih h diffrn of concnraions, iniial ph, and shakn a 150 rpm. Afr finishing ach adsorpion xprimns and phass sparaion by Univrsal 320R cnrifug (Hich Znrifugn) a 6000rpm in 5 minus, h ph of aquous soluion was masurd again o drmin h quilibrium ph by using Orion 4 sar ph mr (Thrmo Scinific). Th rsidual phospha concnraion in h adsorbd soluion was analyzd by SMWW 4500 E mhod [11] and Lambda 35 UV/VIS Spcromr (Prkin Elmr). Th phospha rmoval fficincy is calculad basd on h mass balanc quaion as follows. Whr: C o : Iniial phospha concnraion (mg/l) (1) C : phospha concnraion in h adsorbd soluion a h quilibrium (mg/l) Bsids h adsorpion xprimns, h blank sampl was also carrid ou o nsur ha no adsorpion was aking plac on h wall of h flask usd. 4. Analyical mhods Th chang in chmical composiions and surfac of h ha and acid modifid rd mud bfor and afr adsorpion will b drmind by X-ray Powdr Diffracion (Simns D5005, Grmany) and SEM analysis mhods (Nova Namo Scaning Elcron Microscopy NEP 199). Th wigh rducion of rd mud bfor and afr ha and acid modificaion was drmind by GH 252 analyical balanc (A&D Insrumn Company, England). 3. RESULTS AND DISCUSIONS 1. Effc of iniial ph on phospha rmoval Th ffc of iniial ph on phospha rmoval by C and 1.5M HCl modifid rd mud is prsnd in Fig 1. I is asy o find h sam rnd for boh modifid rd mud, whn iniial ph was 1; 3; 5; 6, h phospha rmoval fficincy incrasd and rachd maximum 82% and 52% wih C and 1.5M HCl modifid rd mud a ph 6.0. Afr ha phospha dcrasd wih h incras of ph. This rnd similar bhavior was also rpord for phospha from aquous soluion by Pradhan [9], Liu Chang-jun [12], and Gnc [13]. Fig 1: Effc of iniial ph on phospha rmoval (Modifid rd mud dos 10g/L, mpraur 25 o C, shaking 150 rpm, iniial phospha concnraion 50 mg/l, conac im 4 hours) 2016, IJISSET Pag 77

3 Inrnaional Journal of Innovaiv Sudis in Scincs and Enginring Tchnology ISSN (Onlin) Volum: 2 Issu: 12 Dcmbr 2016 This rnd occurrd du o h compiion for binding sis among caions and proons a low ph valus. Whil a highr ph, solubiliy of complxs dcrass sufficinly allowing prcipiaion which may complica h sorpion procss and do no bind o h sorpion sis on h surfac of h modifid rd mud [10]. As Kamiyango calculad and rpord [14], h ph ffcs on boh fracion composiions of phospha spcis and charg dvlopmn on h rd mud surfac. In h soluion, phospha xiss undr various forms such as H 2 PO 4-, H 3 PO 4, HPO 4 2-, and PO 4 3- (Fig -2), in h rang of ph from 4.0 o 6.0, phospha is mainly xiss in H 2 PO 4-, which form asy o mal oxids conaining in h rd mud wih h binding nrgy is 135.2V [15]. Whn phospha xiss in h soluion, hn hs sorpion racions ak plac dpnding on ph: SOH + H 3 PO 4 = SH 2 PO 4 + H 2 O (7) SOH+ H 3 PO 4 = SHPO H + + H 2 O (8) SOH +H 3 PO 4 = SPO H + + H 2 O (9) SOH +H 3 PO 4 = SOHPO H + (10) Whr: SOH rprsn sampl surfac of rd mud. Whn h ph incras, h amoun of H 3 PO 4 dcrasd and H 2 PO 4 - and HPO 4 2- wr h prdominan aquous spcis, in h sudy of Shngjiong Yang [16], phospha - mal prcipiaion racion sms o b an alrnaiv xplanaion for phospha adsorpion fficincy, which could b prsnd as: xpo M x+ = M 3 (PO 4 )x (11) Whr: M is h mal componn, such as Al, F, Ca, and Si. Shngjiong Yang also poind ha monovaln dihydrogn phospha (H 2 PO 4- ) was wll adsorbd by rd mud, his ida is h sam wih Kamiyanggo. 2. Effc of conac im Fig 2: Fracion composiion of phospha spcis in h soluion a diffrn ph [14] Kamiyanggo also indicad ha h adsorpion of phospha on Al(OH) 3, FO(OH) is guidd by h AlOH and FOH group, locad on crysal dgs. Whn phospha ion conac wih Al(OH) 3 and FO(OH) will cra h innr sphr complxs bwn phospha and singly coordinad hydroxyl group. Th ligand xchang racion mchanism is prsnd as quaions following: AlOH + H 2 PO 4 - AlH 2 PO 4 + OH - (1) 2 AlOH + H 2 PO 4 - ( Al) 2 HPO 4 + H 2 O + OH - (2) FOH + H 2 PO 4 - FOPO 2 OH+ H 2 O (3) 2 FOH + H 2 PO 4 - (FO) 2 PO 2 + 2H 2 O (4) Th sam poin wih Kamiyango, Liu Chang-Ju [12] also indicad ha a ligand xchang mchanism ook plac in h sorpion of phospha ono h sampls, and h sorpion racion may b wrin wih h following ligand xchang racions. Whn h rd mud was addd ino a soluion, hr xiss such surfac hydrolysis racions dpnding on ph [12]: Conac im is on of h mos ffciv facors in bach adsorpion procss. Adsorpion ra iniially incrasd rapidly, and h opimal rmoval fficincy 82% and 52% was rachd afr 4 hours for 400 o C and 1.5M HCl modifid rd mud, rspcivly. Furhr incras in conac im did no show significan chang in quilibrium concnraion; ha is, h adsorpion phas rachd quilibrium du o h naur of adsorbn and h availabl adsorpion sis affc h ra of adsorpion of phospha. Th mchanism of solu ransfr o h solid includs diffusion hrough h fluid film around h adsorbn paricl and diffusion hrough h pors o h inrnal adsorpion sis. In h iniial sags of adsorpion of phospha, h concnraion gradin bwn h film and h availabl por sis is larg, and hnc h ra of adsorpion is fasr. Th ra of adsorpion dcrass in h lar sags of h adsorpion probably du o h slow por diffusion of h solu ion ino h bulk of h adsorbn [17]. SOH + H + = SOH 2 + (5) SOH = SO - + H + (6) Fig 3: Effc of conac im 2016, IJISSET Pag 78

4 Inrnaional Journal of Innovaiv Sudis in Scincs and Enginring Tchnology ISSN (Onlin) Volum: 2 Issu: 12 Dcmbr 2016 (Iniial phospha concnraion 50mg/L, mpraur 25 o C, rd mud dos 10g/L, iniial ph 6.0, shaking 150rpm) 3. Effc of modifid rd mud dos Th ffc of modifid rd mud dos was sudid in h rang of g/l. I was obsrvd ha h adsorpion prcnag of phospha ion ono h modifid rd mud incrasd rapidly wih h incrasing of adsorbn dos (Fig -4). This rsul is xpcd bcaus h incras of adsorbn dos lads o grar surfac ara. Whn h adsorbn concnraion was incrasd from 2 o 10 g/l, h prcnag of phospha ion adsorpion incrasd from 42.2 and 25.9% o 82 and 52% for 400 o C and 1.5M HCl modifid rd mud, rspcivly. A highr dosag, h quilibrium upak of phospha ion did no incras significanly wih incrasing modifid rd mud dosag. Such bhavior is xpcd du o h sauraion lvl aaind during an adsorpion procss. This finding agrs wih Koumanova.B [18]. For subsqun sudis, a dos of 10 g/l of modifid rd mud was slcd. Fig 5: Effc of iniial phospha concnraion (modifid rd mud dos 10g/L, iniial ph 6.0, mpraur 25 o C, shaking 150rpm, conac im 4 hours) 5. Adsorpion isohrm Th linarizd Langmuir adsorpion isohrm quaion which is valid for monolayr sorpion ono a surfac wih fini numbr of idnical sis is as follows: q Whr: 1 bc (12) q q m m C : h quilibrium concnraion of phospha in soluion (mg.l -1 ), q : h amoun phospha adsorbd a quilibrium (mg/g), q m : h horical maximum adsorpion capaciy (mg/g) b: h Langmuir consan (L/mg). Fig 4: Effc of modifid rd mud dos (Iniial ph 6.0, conac im 4h, mpraur 25 o C, shaking 150rpm, iniial phospha concnraion 50mg/L) 4. Effc of iniial phospha concnraion Th ffc of iniial adsorba concnraion on h adsorpion was invsigad by varying h iniial concnraion of phospha from 25 o 200 mg/l. Th xprimnal daa wr illusrad in Fig -5. Th rsuls indicad ha h incras in h iniial phospha concnraion ld h rmoval fficincy of ha and acid modifid rd mud dcras from 90.2%, 55.33% (whn phospha was 25mg/L) o 46.32% and 28.42% (whn phospha incrasd o 200mg/L). Th dcras can b xplaind by h compiion of amoun of phospha o conac wih h limid of adsorpion sis on h surfac of rd mud. Th linar plo of 1 vrsus wih corrlaion C q cofficin R 2 ovr 0.98 for boh 400 o C and 1.5M HCl modifid rd mud indicas h applicabiliy of Langmuir adsorpion isohrm (Figur 6). This indicas a monolayr sorpion of lad ono h adsorbn surfac. Th maximum adsorpion capaciy q m and binding nrgy consan b of ha and acid modifid rd mud for phospha was 10.2 mg/g and 7.63mg/mg, rspcivly according o Langmuir modl. Fig 6: Langmuir isohrm of phospha adsorpion by modifid rd mud 2016, IJISSET Pag 79

5 Inrnaional Journal of Innovaiv Sudis in Scincs and Enginring Tchnology ISSN (Onlin) Volum: 2 Issu: 12 Dcmbr 2016 Frundlich adsorpion isohrm adops mulilayr adsorpion on hrognous surfacs. Linarizd form of h Frundlich quaion is givn by h following quaion: Whr: 1 ln q ln K f C (13) n q : h amoun of lad ions adsorbd a quilibrium im (mg/g), C : h quilibrium concnraion of lad ions in h soluion (mg/l), K f : h adsorpion capaciy (mg/g), n: an mpirical paramr, Fig 7: Frundlich isohrm of phospha adsorpion by modifid rd mud Th isohrm paramr of boh Langmuir and Frundlich ar shown in Tabl 2. According o R 2 cofficin, i is asy o rlas ha h phospha adsorpion followd boh singl and muli-layr on h surfac of rd mud. Howvr, h Frundlich isohrm provids a br fiing o isohrm han Langmuir isohrm du o h highr R 2. Thrfor, i can b suggsd ha som hrogniy in h surfac of modifid rd mud play a rol in h phospha adsorpion. Tabl 2: Isohrm paramrs of Langmuir and Frundlich for phospha adsorpion 6. Adsorpion kinics Th ra consan K 1 for h adsorpion of phospha was sudid by Lagrgrn ra quaion [19], for iniial phospha concnraion of 50 mg/l. Psudo-firs-ordr ra xprssion of Lagrgrn quaion: log q Whr: K q log q 1 (14) q : Th amoun of phospha adsorbd a h quilibrium (mg/g) q : Th amoun of phospha in h adsorbd soluion a im (min), rspcivly (mg/g) K 1 : Th Psudo-firs-ordr ra consan (min -1 ). Th K 1 and corrlaion cofficin R 2 wr calculad from h slop of h linar plo of log(q q ) vrsus a diffrn im inrvals. Th K 1 and R 2 of boh C and 1.5M HCl modifid rd mud ar shown in Tabl 3 Th Psudo-scond-ordr ra xprssion is: q q 1 (15) K * 2 2 q Whr: K 2 is h Psudo-scond-ordr ra consan (g/mg.min). Th calculaion from h slop and inrcp of h plo q vrsus im was almos linar shown in Fig -9. Th valus of K 1, K 2 and R 2 of boh C and 1.5M HCl modifid rd mud ar shown in Tabl 4 Langmuir isohrm 400 o C modifid rd mud 1.5 M HCl modifid rd mud Frundlich isohrm 400 o C modifid rd mud 1.5 M HCl modifid rd mud Qmax (mg/g) K 0.68 R Qmax (mg/g) 7.63 K 0.14 R n 2.67 Kf 1.45 R n 1.68 Kf 1.71 R Fig 8: Psudo firs ordr Tabl 3: Kinic paramr of Psudo firs ordr Psudo firs ordr K1 q R 2 q * (min -1 ) (mg/g) (mg/g) 400 o C modifid rd mud 0, , M HCl modifid rd mud , IJISSET Pag 80

6 Inrnaional Journal of Innovaiv Sudis in Scincs and Enginring Tchnology ISSN (Onlin) Volum: 2 Issu: 12 Dcmbr 2016 Th incras in surfac ar of rd mud can b sn asily hrough SEM imags (Fig -9), h paricl siz rd mud modifid by ha a 400 o C is fins compard wih raw rd mud as wll as rd mud modifid wih 1.5M HCl soluion. Fig 9: Psudo scond ordr Tabl 4: Kinic paramr of Psudo scond ordr Psudo scond ordr K2, g/mg.min q, mg/g R 2 q * 400 o C modidid rd mud 0,014 4,31 0, M HCl modidid rd mud No: q * is xprimnal valu Th fid curv and paramrs of kinic modls ar shown in Fig -8, Fig -9 and Tabl 3, Tabl 4. I is clar ha h phospha adsorpion procss on modifid rd mud is wll dscribd by h Psudo scond-ordr modl bcaus of h high corrlaion cofficin R 2 was and for ha and acid modifid rd mud compard o R 2 was 0.91 and 0.93 by Psudo firsordr. According o h rsuls inroducd abov, i can b suggs ha h phospha adsorpion by rd mud modifid by ha a 400 o C is mor ffciv han acid mhod wih 1.5M HCl soluion du o h incras in ara surfac. Afr ha modificaion h ara surfac of rd mud was masurd abou m 2 /g highr han 11.85% and 13.73% compard o rd mud modifid by acid (88.83m 2 /g) and raw rd mud (86.95m 2 /g), rspcivly. Bsids, som chmical composiions of modifid rd mud wr found o dcras in conn. In h dail, som lmns conn in rd mud modifid wih 1.5M HCl soluion wr found o dcras such as FO(OH), F 2 O 3. CaTiSiO 5, CaCO 3 hn hs lmns conn in rd mud modifid by ha a 400 o C wr found o incras, spcially CaTiSiO 5 and CaCO 3 conn wr highr wic im. I is considrd as a caus of phospha adsorpion capaciy of ha modifid rd highr han acid modifid rd mud (Fig - 8) Fig 9: SEM imags of rd mud bfor and afr 400 o and 1.5M HCl modificaion As shown in Fig 10, ɣfo(oh), Al(OH) 3, FO(OH), F 2 O 3, CaTiSiO 5 wr dcd on h surfac of modifid rd mud bfor phospha adsorpion. Afr h adsorpion procss, wo srang paks (4.25A o and 2.25A o ) appard on h spcrum, which dmonsrad ha phospha was succssfully adsorbd ono h surfac of modifid rd mud. Alhough h XRD s paks did no indica xacly h form of phospha appard afr adsorpion, bu basd on Barbaux s rpor, phospha could rac wih FO + and Al(OH) 3 by h prcipiaion and ion xchang mchanism [20] or h formd phospha complxs including [FOPO 4 ] adsorpion spcis and [Al(OH) 3 - PO 4 ] adsorpion spcis could also adsorb addiional H 3 PO 4 analog by hydrogn bonding [21]. Fig 10: XRD analysis rsuls of 400 o C modifid rd mud bfor and afr adsorpion 7. Modificaion cos Th phospha rmoval fficincy of rd mud modifid by ha and acid was no only invsigad on h adsorpion capaciy, bu also compard on h modificaion cos. Th daa inroducd in Tabl 5 is h comparison of cos modificaion by ha and acid. Fig-8: XRD analysis rsuls of rd mud afr ha and acid modificaion I is asy o rlas ha o modifying h sam amoun of raw rd mud (1kg), ha mhod is a vry low cos and simpl compard o acid mhod. Bsids, ha 2016, IJISSET Pag 81

7 Inrnaional Journal of Innovaiv Sudis in Scincs and Enginring Tchnology ISSN (Onlin) Volum: 2 Issu: 12 Dcmbr 2016 mhod is also frindlir o nvironmn du o wihou flu gass as wll as aquous soluion gnraion and modificaion cos was USD only, whil acid mhod gnrad 10 lir of HCl soluion and HCl gas during modificaion and modificaion cos up o USD, highr han 10 ims compard o ha modificaion. Tabl 5: Modificaion cos of rd mud Thrmal modificaion mhod Modificaion im : 1h Typ of furnac: Lnon (England) Capaciy : 1.9KW Max mpraur : 800 o C Elcric consumpion (kwh) Cos (USD) Tmpraur modificaion: 400 o C Elcric consumpion 0.95 Cos/KWh 0.25 Was gnraion (flu Non gass, was war) Modificaion cos HCl modificaion mhod Modificaion im: 2h Har : Max mpraur: 300 o C Capaciy: 0.625KW Tmp. modificaion: 0.333KWh o C Elcric consumpion Sirrr: Max sirring spd: 1200rpm Sirring spd: 300rpm 0.063KWh Capaciy: 0.125KW HCl (indusrial qualiy USD/Lir) HCl consumpion: lir Was gnraion (flu gass, was war) 10 lirs of was HCl soluion HCl gas Dionizd war for nuralizaion Modificaion cos CONCLUSION According o h rsuls obaind in his sudy, som conclusion can b rcommndd as follow: Iniial ph, iniial phospha concnraion, conac im, modifid rd mud dos could influnc h phospha adsorpion prformanc of 400 o C and 1.5M HCl modifid rd mud significanly. Th kinic and isohrm of phospha adsorpion ono h surfac of boh 400 o C and 1.5M HCl modifid rd mud wr wll dscribd by Psudo scond ordr and Langmuir Frundlich isohrm, which dmonsrad ha h phospha adsorpion ono 400 o C and 1.5M HCl modifid rd mud could b govrnd by mulipl mchanisms. Ha modificaion of rd mud a 400 o C in 1hour is an ffciv and lowr cos compard acid modificaion mhod wih HCl 1.5 M soluion. Th adsorpion capaciy of 400 o C modifid rd mud highr 30% and modificaion cos 0.237USD/kg of raw rd mud only, 10 ims lowr han acid modificaion wih modificaion cos 3.431USD/kg of raw rd mud. REFFERENCES [1] Nguyn Canh Nha (2005), Bauxi naural rsourc in Vinam and h primary rsul of nrichmn bauxi or in h Souhrn of Vinam, Procding of h scond Naional minral rsourcs, Hanoi, Nov 2005 [2] Ramsh Chandra Sahu, Rajkishor Pal, Bankim Chandra Ray, Adsorpion of Zn(II) on acivad rd mud: Nuralizd by CO 2, [3] C-J.Liu, Y-Z.Li, Z-K.luan, Z.Y.Chn, Z-G.Zhang, Z- P.Lia, Adsorpion rmoval of phospha from aquous soluion by aciv rd mud, J.Environ.Sci, 2007, vol. 19, pp [4] Iman Mobashrpour, EsmailSalahi, Ali Asjodi Rsarch on h bach and fixd-bd column prformanc of rd mud adsorbns for lad rmoval, [5] VslinkaV. Gru, Sorpion of cadmium from war using nuralizd rd mud and acivad nuralizd rd mud, ARPN Journal of Enginring and Applid Scinc, 2013, vol. 8, No11, pp [6] Hayrunnisa Nadaroglu, Ekrm Kalkan, Rmoval of cobal (I) ion from aquous soluion by using alrnaiv adsorbn indusrial rd mud was marial, Inrnaional Journal of Physical Scincs, 2012, vol. 7(9), pp [7] H.S.Alundogan, S. Alundogan, F.Tumn, M.Bildik, Arsnic adsorpion from aquous soluion by adsorpion on rd mud, War Manag, 2002, vol. 20, pp , IJISSET Pag 82

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