TAP CHI HOA HOC
DOI 10 IS625'0866'7I442014-0008
T 52(4)439-442 THANG 8 N A M 2014
T 6 N G H Q P N A N O Ti02 CAU TRUC ANATASE PHA TAP NEODYMIUM BANG PHU'aNG PHAP SOL-GEL
Vu Hong Sffn*, Le Phiic Son
Vi^n Khoa hgc Vdt lieu, Vi^n Hdn ldm Khoa hgc vd Cong nghi Viet Nam Ddn Tda soan 21-12-2013
Abstract
A series of photo catalysts Nd/Ti02 powders have been prepared by the sol-^el technique with neodymium nitrate and tetra-n-butyl titanium as raw materials, and their characteristics evaluated by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectra (UV-Vis), scanning electron microscopy (SEM). SEM photograph showed that Nd/Ti02 were about 50 nm in diameter. Neodymium doped Ti02 has obvious absorption in the visible light. The catalytic efficiency was tested by monitoring the photo-catalytic conversion of CO in visible light. The results showed that when the doping content was 0.4 % Nd mass, the conversion of CO achieved at 83 %.
Keywords: Anatase TiOz, Neodymium doping, photo-catalytic, visible light.
1. MO DAU
TiOj cd nhieu uu diem nhu: dg ban cao, khong dge, khi nang quang hda va gia thanh thap [1]. Ti02 ed nhieu ung dyng trong ITnh vyc nhu: chd tao pin m$t trdi, cam biln khi, irng dyng quang xiic tac lam sgch nudc va khdng khi, cha tao bpt nen cho cdng nghp hda my pham, nhugm mau, cdng nghp ty lam sach... Ti02 d dgng cau hinh anatase ludn cd hipu irng quang hda cao han cac dgng tbii hinh khac [2].
Tuy nhien miic nang lugng viing cam 3,2 eV tuang duang vdi lugng tir anh sang cd budc song 388 nm, da hgn che img dyng ciia Ti02 d viing anh sang nhin thay. Da kich hogt kha nang quang hda ciia Ti02 d vimg anh sang nhin thay, ngudi ta tien hanh pha tap cac nguyen td khac nhu: kim logi chuyan tiep V, Cr, Mo, Fe... cac nguyen td phi kim N, F... va kim logi thupc hg dlt hiem [3,4].
Cac nghian cuu trudc day da chi ra ring, cac nguyen to dlt hiem nhu Ce, La, Sc... khdng chi md rpng nang lugng ho|it dgng cua Ti02 sang viing anh sang nhin thly ma cdn tang cudng kha nang hap thy bem$tcuaTiOi[5, 6].
Trong nghien ciru nay, chiing tdi tian hanh tdng hpp xuc tac quang hda TiQj cd pha tgp nguyen td dat hiem neodymium (Nd) blng phuang phap sol-gel va tien hanh thii- nghipm kha nang quang hda ciia xuc tfic dya tren chuyen hda CO.
2. THI/C NGHIEM 2.L Hda chat, d^iDg cy
Cac hda chat sir dung trong thyc nghipm:
Tetrabutyl titanate, neodymium nitrate, etanol, diethanolamine, deu d dgng tinh khiat ma khdng can cha hda bo sung.
Cdc chju nhipt 100 ml, 200 ml, 500 ml, binh dinh muc 25 ml, 100 ml, 250 ml, 500 ml, pipet, may khuay tir, con khuay tir, pheu nhd rgt. Id nung, chen nung, til sly, may cd quay chan khdng.
2.2. Tong hgp xuc tac
Xuc tac quang hda Ti02 cd pha tgp neodymium Nd dugc tdng hgp theo quy trinh sau [7]:
Chuan bi dung dich A cd chira 9,5 ml Ti(OBu)^;
21 inl C2H5OH; 3,5 ml NH(C2H50)2. Dung dich A khuay deu trong 30 phut d nhipt dg phong. Sau 30 phut khuay thu dugc dung dich cd mau vang nhat,
Chuan hi dung djch B cd chiia 10 ml C2H5OH, 3 ml H2O va 9,5x10"^ g Nd(N03)3. Khuiy d^u dung dich B trong 30 phiit, bda tan hoan toan Nd(N03)3.
Dung dich B dugc nhd rgt tir tir vao dung djch A, khuay deu trong vdng 2 tidng d nhipt dp phdng.
Dung djch sau khi dugc tdng hgp, tien hanh bay hoi het dung mdi hiru ca blng may cd quay chan khdng d nhipt dp phdng trong vdng I tieng. Gel tdng hgp dugc dem say khd trong Id nung d nhipt dp 550 °C.
Lugng NdCN03)3 cd trong dung djch B va TiOj cd ti Ip Nd chiem 0,3 % (ty Ip 0,3 % tuang irng vdi 9,5x10'^ g Nd(N03)3), 0,4 % va 0,5 % khdi lugng.
Ky hipu cac mau tucmg ung la TN2, TN3 va TN4.
Khi khdng cho Nd(N03)3 vao trong dung d|ch B, quy trinh diau che nhu tren se thu dugc Ti02 diing dc
TCHH, T. 52(4), 2014
so sanh. M5u dii nghiem nay dugc ky hieu la TN 1.
2 J . Phirong phap xac dinh dac trimg can true va boat tinh xuc tac
Xac dinh clu true vgt lieu blng phuang phap nhilu xg tia X tren may SIEMENS D5000.
Phd hip diu UV-Vis cua vat lieu Ti02 dugc do tren may CARRY 5000 UV-Vis-NIR.
Dipn tich bd mgt rieng BET dugc xac dinh yen may Quantachrome V3.0.
Xac djnh kich tiiudc hgt blng may SEM Hitachi S-4800.
Hoat tinh quang hda ciia xiic tac dugc danh gia dya tran kha nang chuyen hda CO dugc tbuc hipn tran h? thiat bi chuyen dyng ciia Vien Khoa hgc Vgt lieu.
va HSng San vd cgng s^
3. KET QUA VA T H A O LUAN
3.1. Cau true tinh the, kich thu-ore hat va di^n tich be mat rieng BET
Hinh 1 la gian dd nhilu x | tla X vdi mlu TiOj khdng pha tap (TNI) va cac mau Ti02 pha tgp vdi ty le 0,3 %, 0,4 %, 0,5 % Nd (TN2, TN3, TN4). Gian dd cho thly cac mau Ti02 va Nd/TiO; chi xuat hi?n cac pic dac tnmg cua Ti02 dang anatase, khdng xult hien cac pic dac trung ciia Nd. Mau Ti02 so sanh didu cha dugc (TNI) tdn tai d dgng anatase. Vi?c khdng xult hien cac pic dac trung ciia Nd cho thly Nd da dugc dua vao mang tinh the ciia Ti02 de tgo thanh pha mdi.
2 theta C)
Hmh J: Gian dd nhilu xg tia X cua cac mau TNI (a), TN2 (b), TN3 (c) va TN4 (d)
Kich thudc tinh the ciia pha anatase c6 tha dugc tinh theo phuang trinh Scherrer:
d = KypcosO
trong do: X la budc sdng ciia tia birc xg X, nm; K la blng sd K = 0,89; p la ia do rgng Vi chieu cao cyc dgi Clia vgch phd dac trung; 9 la gdc nhieu xa Bragg, 26 = 25,3 tuang ung vdi Ti02 anatase.
Hinh thai va kich thudc hgt cua cac mau xuc tac dugc tha hipn qua anb SEM tren hinh 2. Cac mau Nd/Ti02 cd kich thudc hat nhd tgp trung trong khoang tir 40-50 nm. Hat ciia mau cd pha tap Nd tuang ddi dong dau, cd dgng hinh clu. Anh SEM ciia mau so sanh TNI cung cho thay rang, khi chua pha tgp Nd, cac hgt tinh tha Ti02 cd kich thudc khoang 80-100 nm.
Bdng I: Dien tich be mat rieng ciia vgt lipu
Mau TNI TN2 TN3 TN4
Dien tich be mat rieng BET, mVg 9,319 12,462 14,825 13,479
Kdt qua xac dinh dipn tich be mgt (BET) ciia TiOj va Nd/Ti02 dugc trinh bay trong bang 1. Di^n tich be mat ciia mau Ti02 chua pha tgp cd dipn tich nhd ban so vdi cac mau pha tgp. Mau TN3 tuong ung vdi ty Ip Nd 0,4 % cd dipn tich Idn nhat.
TCHH, T. 52(4), 2014 32. Pho hap thu UV-Vis-NlR
Kha nang hap thy anh sang ciia mSu TiOj va Nd/TiO; diriyc xac djnh thong qua ph6 hip thif UV- Vis. Kk qua dinjc the hifn tren hinh 3. Mlu TiOz chua pha tap^ gan nhu khong hap thu anh sang a viing nhin thly (hinh 3). Cac mlu TiO; pha tiip Nd
Tong hop nano TiOi cau trite...
CO kha nang hap thy anh sang m^mh o viing buoc song dai hon, sang viing anh sang nhin thay. Djng duong hip thu ciia cac mlu TN2, TN3, TN4 tuong tu nhau nhimg cuong do hip thy anh sang tang khi ham lu?ng Nd pha t?p tang va djt cyc dai khi ham luong Nd bang 0,4 %.
^.- ' ^ ^ ' ^ V^:' ^^
(a) ^ (b) Hmh 2: Anh SEM cua mlu TN3 (a) va TN 1 (b)
600 700 800 Budc sdng, nm
Hmh 3: Pho hap thy UV-Vis ciia Ti02 (d) va Nd/TiOj (TN2 - b, TN3 - a, TN4 - c) 3.3. Dp chuyen hda CO
Cdc mSu Ti02 cd pha tgp Nd hap thy mgnh anh sang d viing 400-600 nm, dugc tian hanh khao sat hogt tinh quang xiic tac dya tren sy chuyen hda CO ddieu kipn nhipt dg phdng dudi anh sang mgt trdi.
Phan ling chuyin hda CO dugc thyc hipn nhu sau: lay 0,2 g mau thi nghipm cho vao dng phan irng, dong CO vdi ham lugng ban dau la 1000 ppm dugc dan qua xiic tac lien tyc, sau khoang 15 phiit gia tri CO dau ra dn dinh se ghi Igi ket qua dl danb gia kha nang chuyen hda ciia xiic tac. Bang 2 la ket qua ciia phan img chuydn hda CO.
Bdng 2: Ket qua chuyen hda CO Thi nghidm
TN2 TN3 TN4
Nong dQ CO ban dau, ppm 1000 1000 1000
Nong dg CO sau phan img, ppm 150
70 100
Hi?u suat phan img, % 75 83 80
TCHH, T. 52(4), 2014
Hipu suat phan ung quang xiic tac chuyen hda CO kha cao, 75-83 %. Miu TN3 cd hieu suit phan irng cao nhat, mlu nay tuang irng vdi dipn tich be mat ldn nhat va chung td rang khi dien tich be mat tang len thl kha nang tiep xiic giira khi CO dau vao va mau xiic tac ciing tang len. Cac mau xuc tac boat ddng tdt dudi dieu kien anh sang mat trdi, nhiet dp phdng, md ra kha nang iing dung, xu ly cac chat gay 6 nhiem mdi trudng hieu qua.
4. KET LUAN
- Pha tap neodymium Nd vao Ti02 da lam thay ddi thanh phan va tinh chat ciia Ti02 nhu md rdng viing anh sang hip thy, thay ddi thanh phan pha, kich thudc hgt va dipn tich ba mat. Mau bgt Nd/Ti02 anatase thu dugc ddng nhat cd kich thudc khoang 50 nm, vdi dipn tich be mgt rieng 14,825 mVg.
- Dudi hire xg cua anh sang mat trdi cac mlu xiic tac Nd/Ti02 cd hogt tinh quang xiic tac tdt, cd kha nang chuyen hda tdi 83 % CO.
T A I L I E U THAM K H A O
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Lien h$: Vu Hong San
Phong hda hpc va vat lieu xiic tac, Vipn Khoa hgc Vgt lieu Vipn Han lam Khoa hgc va Cdng nghp Viet Nam Nha B2, P305, So 18 Dudng Hoang Quoc Viet, HaNdi Email: [email protected]
Di dgng: 0986 586 986.