TỔNG HỢP NANO TIO2 DẠNG Ố 2 NANOTUBES) BẰNG · PDF filehuỳnh quang tia X (XRF)...

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  • TP CH KHOA HC V CNG NGH, I HC NNG - S 1(42).2011

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    TNG HP NANO TIO2 DNG NG (TIO2 NANOTUBES) BNG PHNG PHP THY NHIT

    SYNTHESIS OF TIO2 NANOTUBES FROM COMMERCIAL TIO2 VIA A HYDROTHERMAL METHOD

    Phm Nh Phng, Phan Thanh Sn, L Vn Long,

    Nguyn Ngc Tun, Nguyn nh Lm Trng i hc Bch khoa, i hc Nng

    TM TT Nano TiO2 dng ng c tng hp t TiO2 thng mi bng phng php thy nhit

    t huyn ph TiO2 thng mi trong NaOH m c ln u tin c tng hp thnh cng ti trng i hc Bch khoa i hc Nng. Sn phm thu c c cu trc dng nano ng ng nht. Cc tnh cht c trng ca TiO2 nanotubes (TNT) c nh gi bng cc phng php ha l hin i: nhiu x tia X (XRD), hp ph ng nhit N2 77K v xc nh b mt ring theo l thuyt BET, knh hin vi in t qut (SEM), v knh hin vi in t truyn qua (TEM) cho thy TNTs c cu trc ch yu l pha anatase, c b mt ring c tng cng v ln gp khong 8,5 ln so vi TiO2 nguyn liu ban u, cu trc ca TNT dng ng vi ng knh c kch thc nano v ng nht c 7nm. Hot tnh quang ha ca TNT c tng ln nhiu ln v c kim chng bng qu trnh kh lu hunh su nhin liu diesel.

    ABSTRACT TiO2 nanotubes have been successfully synthesized via a hydrothermal synthesis, from the

    suspension of commercial TiO2 in concentrated sodium solution at Da Nang University of technology. The obtained products have the structure of homogenous nano-tubular form. The synthesized TiO2 nanotubes have been characterized by the modern physicochemical techniques such as X ray diffraction (XRD), N2 adsorption desorption isotherm measurements using the BET theory for determining the specific area surface, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). This physicochemical characterization proves that TiO2 nanotubes (TNT) is essentially formed by the anatase phase, very high specific area surface, 8.5 times higher than the commercial TiO2, with the diameter of about 7 nm. The photo-catalytic activity of our TiO2 nanotubes has been well enhanced and confirmed by deep desulfurization of diesel.

    1. Gii thiu Vt liu Titandioxide c cu trc nano ng TiO2 nanotubes (TNT) v ang

    c nhiu nh khoa hc quan tm nh vo kh nng ng dng a dng ca n trong nhiu lnh vc nh: t bo quang in mt tri[1-3], cm bin kh[4-5], pin nhin liu, cc thit b quang in, xc tc quang ha, cng ngh t lm sch[6], quang in phn nc to hydro[7]... Trong nhng nm gn y vt liu TiO2 c cu trc nano nh nano si, nano ng, nano thanh c tng hp thnh cng. Trong TNT vi nhng u im nh b mt ring ln, cu trc dng ng, c kh nng trao i ion v kh nng quang ha rt thun li cho cc phn ng[8].

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    Hin nay c cc phng php tng hp nano TiO2 ng nh: Oxy ha bng phng php in ha trn in cc anot, phng php s dng hp cht to cu trc, phng php thy nhit... Da trn cc nh gi tng quan v yu t sn xut, tnh cht, c ch phn ng v cc ng dng tng ng ca nano TiO2 ng thc hin bi cc phng php trn so vi phng php thy nhit, hoc l khng thch hp vi quy m ln, hoc l hiu qu tch, kt tinh cc ng nano thp[9]. Vi nhng u im nh chi ph hiu qu, d dng to c cc ng TiO2 nano v tnh kh thi, kh dng rng ri chng ti la chn phng php thy nhit v tng hp thnh cng nano TiO2 dng ng c pha tinh th ch yu l anatase t ngun TiO2 thng mi dng bt, sn c trn th trng Vit Nam. Nano TiO2 ng vi ng knh ng nht c kch thc khong 7nm c tng hp bng phng php thy nhit v qua qu trnh x l trao i ion, sau nung nhit cao. Hot tnh quang ha ca nano TiO2 ng s c kim tra bng kh nng kh lu hunh trong du Diesel.

    Trong phm vi bi bo ny, chng ti s trnh by cc kt qu ca vic tng hp t nano TiO2 dng ng t TiO2 thng mi, l ngun nguyn liu d kim, khng c hi v r tin, ln u tin c thc hin thnh cng ti trng i hc Bch khoa, i hc Nng.

    2. Thc nghim

    2.1 Tng hp nano TiO2 dng ng t TiO2 thng mi Nano TiO2 dng ng c tng hp t nguyn liu ban u l bt TiO2, mt sn

    phm thng mi ( tinh khit 99,4%), kch thc ht trung bnh khong 0,13m c cung cp trn th trng bi cng ty TNHH ROHA Dyechem Vit Nam, c s dng trc tip khng qua bt k qu trnh x l no. Qu trnh tng hp theo phng php thy nhit i c tin hnh nh sau: Bt TiO2 thng mi c phn tn trong dung dch NaOH m c bng my khuy t trong 1 h, huyn ph ny sau c chuyn sang thit b Autoclave vi lp lt bng Teflon. Qu trnh tng hp thy nhit c tin hnh trong khong nhit t 130 180oC vi thi gian tng hp t 12 36h. T l mol TiO2 :NaOH l 1:20 1:30. Kt thc qu trnh thy nhit, cht rn trong Autoclave c lc, ra sch bng nc ct ri ngm trong dung dch axit HCl long trong 1 gi. Sau , sn phm c ra li bng nc ct cho n pH trung tnh. Sau , c sy kh 100 oC ri nung trong khng kh ti nhit 500oC trong 2h.

    2.2 Cc phng php nh gi c trng Sn phm thu c c nh gi c trng bng cc phng php ha l hin

    i: nhiu x tia X (XRD), hp ph ng nhit N2 77K v xc nh b mt ring theo l thuyt BET, hnh thi ca sn phm c chng minh bng hin vi in t qut (SEM) v hin vi in t truyn qua (TEM). Gin nhiu x tia X c ghi li trong gc qut 2 t 10 80o nh my D8 advance ca hng Bruker, s dng s pht x Cu K1 ( = 0,16 ) l ngun pht x tia X, thit b c trang b mt u d phn tn nng lng SOL XE. Sn phm c nghin cu hp ph ng nhit N2 77K trn

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    thit b chuyn dng Model BET 201A v xc nh b mt ring theo l thuyt BET. nh hin vi in t qut (SEM) c thc hin nh thit b SEM S 4 800 ca hng Hitachi. nh hin vi in t truyn qua c quan st nh thit b JEOL JEM 1010 (80 kV), trong k thut ny mu c phn tn trong ethanol nh sng siu m v sau chuyn ln mt li bng ng c ph cacbon.

    2.3. Kim tra hot tnh quang ha ca nano TiO2 dng ng bng cch x l lu hunh trong du diesel

    Diesel thng mi (DO 2500) sau khi mua v c x l bng hp ph qua ct silicagel loi b cc hp cht gy mu v cc hp cht cha lu hunh b -xy ha trong qu trnh lu tr v vn chuyn (Sulfoxide v sulfone). Hm lng lu hunh cn li sau khi hp ph s b l 807 ppm. Nhin liu Diesel ny sau c x l bng TiO2 thng mi v nano TiO2 ng (1g xc tc cho 100 ml du diesel) di tc dng ca bc x t n cao p hi thy ngn (OSRAM 250W) c s dng nh mt ngun pht quang ph mt tri (nh sng trng). Mu c ly ra tun t t thit b phn ng theo thi gian 20, 40, 60, 80, 100 v 120 pht c ly tm tch xc tc v em i hp ph Sulfone bng silicagel trc khi em xc nh hm lng lu hunh bng phng php hunh quang tia X (XRF) trn my TS 100V ca hng MITSHUBISHI. S h thng thit b -xy ha quang ha v hp ph lu hunh c trnh by trn hnh 1.

    Hnh 1. Thit b phn ng quang ha v hp ph lu hunh trong nhin liu diesel

    3. Kt qu v bin lun

    3.1. Kt qu v hnh thi cu trc ca TiO2 nanotubes tng hp t TiO2 thng mi dng ht

    Sn phm TiO2 nanotube c thu nh trn knh hin vi in t truyn qua (TEM) v knh hin vi in t qut (SEM). nh thu c c so snh vi cu trc ca nguyn liu bt TiO2. Kt qu ca cc nghin cu ny c trnh by trn hnh 2 v hnh 3 cho thy rng nguyn liu TiO2 thng mi c dng bt ban u vi kch thc micro chuyn ha hon ton thnh TiO2 nanotubes dng ng vi ng knh n nh trong khong 7 v hon ton khng tm thy cc cu trc khc trong sn phm TiO2 nanotubes.

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    Hnh2. nh thu c t knh hin vi in t truyn qua (TEM) ca TiO2 thng mi (a) v TiO2 nanotubes (b)

    Hnh 3. nh thu c t knh hin vi in t qut (SEM) ca TiO2 thng mi (c) v TiO2 nanotubes (d)

    Cu trc pha ca sn phm nano TiO2 dng ng c khng nh bng phng php nhiu x tia X (XRD) c cu trc ch yu l pha annatase, pha c hot tnh quang ha cao ca TiO2. Kt qu nghin cu bng XRD ca nguyn liu v sn phm ca qu trnh tng hp thy nhit c trnh by trn hnh 4 cho thy cu trc pha ca TiO2 c bo ton. Tn hiu nhiu x trn sn phm nano TiO2 ng c phn gii nh hn l hon ton ph hp vi kt qu c xc nhn nh khi nghin cu bng knh hin vi in t, mt ln na khng nh cu trc nano ca sn phm TiO2 thu c bng phng php thy nhit.

    Hnh 4. Kt qu nhiu x tia X (XRD) ca TiO2 thng mi (a) v nano TiO2 ng (b)

    (c) (d)

    (a) (b)

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    B mt ring ca nguyn liu TiO2 thng mi v nano TiO2 ng tng hp c xc nh bng phng php hp ph ng nhit N2 77K v c so snh v trnh by trn hnh 5.

    Hnh 5. Hp ph v gii hp ng nhit ca TiO2 thng mi v nano TiO2 ng.

    Kt qu thu c trn hnh 5 cho thy rng b mt ring ca sn phm nano TiO2 ng ln gp 8,5 ln so vi b mt ring ca TiO2 nguyn liu ban u, ng thi qu trnh tng hp bng phng php thy nhit cng gim ng k phn b mt vi xp (micropore) xung cn 0,8m2.g-1, y l mt li th ng k khi s dng sn phm nano TiO2 ng lm xc tc v s hn ch c s khng ch khuch tn trong cc l vi xp nh thng gp trn cc loi xc tc thng dng.

    3.2. So snh hot tnh quang ha ca nano TiO2 ng v bt TiO2 thng mi Nh trnh by trn hnh 2 v hnh 3, TiO2 thng mi c cu trc dng ht vi

    kch thc micro, khong 0,10 0,13m c bin tnh thnh nano TiO2 ng c cu trc dng ng vi ng knh ng trung bnh t 7nm. Hot tnh quang ha cao ca nano TiO2 ng cn c kim tra bng qu trnh kh lu hunh trong du diesel, kt qu trong th hnh 6, ch sau 20 pht phn ng di nh sng n cao p, hm lng lu hunh gim xung rt thp (19 ppm) v hon ton ht sau 40 pht cho thy hot tnh quang xc tc cao ca nano TiO2 ng.

    Hnh 6. Mi quan h gia thi gian phn ng quang ha trn xc tc TiO2 thng mi

    v nano TiO2 ng vai hm lng lu hunh cn li trong nhin liu diesel.

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    4. Kt lun

    Bng phng php thy nhit, ln u tin ti Trng i hc Bch khoa i hc Nng tng hp thnh cng nano TiO2 dng ng t bt TiO2 thng mi. Cc phng php phn tch ha l cho thy cu trc pha anatase ca nano TiO2 dng ng c bo ton vi kch thc nano trong khong 7nm. S gia tng b mt ring ln hn 8 ln v gn nh khng c l vi xp tng mnh kh nng quang ha ca xc tc v c khng nh qua qu trnh kh lu hunh su nhin liu diesel bng phng php -xy ha quang ha.

    TI LIU THAM KHO

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    126 (2004) 14943. [3] M. Drr, A. Schmid,M. Obermaier, S. Rosselli, A. Yasuda, G. Nelles, Nat. Mater.

    4 (2005) 607. [4] L.R. Skubal, N.K. Meshkov, M.C. Vogt, J. Photochem. Photobiol., A Chem. 148

    (2002) 103. [5] K.R. Meier, M. Gratzel, ChemPhysChem 3 (2002) 371. [6] A.