TAP CHI H6A HOC T 50(4) 492-497 THANG NAM 2012 ANH HU'6'NG CUA W(VI) D £ N CAU TRUC VA HOAT T I N H QUANG XUC TAC CUA B Q T W-TiOz KJCH THU-b-C NANO DWgC DltU CH^ B A N G PHU'aNG P H A P T H U Y PHAN Nguyen Vfln Hung'', NgdSp Luvng^ 'Khoa Hda hgc, Trudng Dgi hgc Ddng Thdp ^Khoa Hda bgc Trudng Dgi hgc Khoa hgc Tu nhien, DHQG Hd Ndi Din Tdasogn 22-4-2012 Abstract Nano-sized W(VI)-dopcd TiOj and pure TiOj powders were synlheslzed successfully by hydrolysis method from precursors TiOSO^ and {NH4)6H;W|20jo wiih presenting urea The prepared products were characterized by XRD, UVVIS, TEM BET and XPS methods Experimental results showed that the obtained W-TiOj powders were single phase anatase, small particle size (-13-14 nm), regular particle distribution and large specific surface area (67.4 m'/g) Moreover, the existing of W(VI) in the crystal lattice had been narrowed significantly ihc band gap energy of TiOj (Eg in ^out 2.25-2.28 eV) Sample W-Ti02 with W/TiOj molar ratio = 0.1% had the highest pholo-calalytic activity Methylene blue in aqueous solution was nearly completely decomposed after irradiation in Ih and 1.65 times higher than TiO^ sample without doping Keywords: Titanium dioxide, photocatalyst, hydrolysis, W-T1O2 doping, W(V1) I.GIOITHIEU Ti02 Id chit quang xue tdc (QXT) hua h?n nhat cho viec xu ly d nhilm mdi trudng vd gidi quyet van de khiing hoang ndng lupng tuong lai [1] Tuy nhien, nang lupng viing cam cua Ti02 khd Idn (3,05 eV ddi vdi anata vd 3,25 eV doi vdi rutin) n6n chi ho^t dpng QXT vijng tu ngo?i gan vd dd ban che khd ndng tdn dyng nguon ndng lupng m$t trdi vd gidi han ung dyng thyc tiln cua nd ,Yi vgy, nhi6u ion kim lo^i, ddc bi^t Id cdc ion kim lo^i chuyen tilp da dupe su dyng de biln tinh cdc d^ng thill hinh khac ciia Ti02 nh5m ndng cao hon niJa hogt tinh QXT cCia TiO: vung dnh sdng nhin thdy Do bdn kinh ion W(VI) (0,065 nm) tuong d6ng vdi bdn kinh ion Ti(IV) (0,062 nm) [2] nen ion Ti(IV) dl ddng dupe thay the bdi ion W(VI) mfuig ludi Ti02, gay nhiing thay doi cd vl tinh chdt bl mdt ldn d3c tinh cau true ldng hgt xiic tdc vd dd cd thi giiip TiOz hogt dpng QXT hi?u qud hon viing dnh sdng khd kien A Kubacka [3] da dilu che cdc vgt li?u TiOz dupe bien tfnh bdi (V, Mo, Nb, W) bdng phuong phdp vi nhu tuong K6t qud cho thdy, W(V1) de dang thav the Ion Ti(IV) ludi T1O2 de hinh thdnh lien kit dgng Ti-W vd dd thu h?p ddng ke ndng lupng viing cam ciia Ti02 Tat cd cdc mau Ti02 dupe biln tinh vdi cdc ion tren deu cd khd ndng phan hQy quang dung djch toluen cao hon so vdi mlu TiO: khdng biln tinh dudi hue xa cua dnh sdng mdt trdi Cd nhieu phuong phdp dilu chi vgt Ii?u Ti02 bien tinh, nhung phuong phdp thCiy phdn dong thi dung djch muoi vd co chua Ti(lV) (TiCU TiOS04, ) cd mdt ure Id phuong phdp don gidn, co the dl ddng thyc thi san xu^t, tgo ch4t QXT cd gid thdnh thap, di?n tich be mdt Idn vd khd ndng QXT cao [4] Vi?c chpn ch^t dau Id TiOS04 va tien hdnh thuy phdn dilu ki§n cd mjt ur6 theo chung tdi cd mOt s6 uu diem ndi trpi Thu nhdt, sy cd mdt cua ion S04^" cd the giup cdi thi^n di^n tich bl m$t va tdng cudng tinh axit tren be m$t TiOi Cac kit qua ndy tgo dieu ki^n thudn Ipi dl TiO] hap phy H2O len bl m$t vd chuyen chiing thdnh cdc goc hydroxyl hogt dOng (•OH) nfin tdng cudng hogt tinh QXT cila Ti02 Thu hai, khdc vdi qud trinh ihiiy phan bdi cdc chit ket tiia bazo nhu NaOH, dung djch NH3 , cdc phdn tii ure CO(NH2)2 cd nhdm -NH2 ddng vai trd nhu la chit hogt dOng be mjt va bj dun ndng se phdn hiij; cho NH3 mpt cdch tir ti> vd ddng dlu toan bO thi tich dung djch nen trdnh dupe hi^n tupng kit tua viing, d6ng thdi cd the ldm gidm kfch thudc hgt, tdng di?n tich be mdt vd miic dp ket tinh ciia sdn phim bOt • Ti02 dieu che dupe Tuy nhiSn, vi?c dilu chi bpt TiOj biln tinh bdi W(VI) bdng phuong phdp thCiy phan van chua dirpc cdng b6 492 Trong cdng trinh ndy, chfing tdi thdng bdo m8t TCHH, T 50(4), 2012 s6 kit qud nghiSn cuu ve dnh hudng ciia n^ng dO urd vd W(VI) den cau tr6c vd tinh chdt ciia bpt TiO^ dupe dilu chi b^ng phuong phdp thiiy phdn dhng the dung djch TiOS04 cd m§t urfi vd ddnh gid hogt tinh QXT ciia nd thdng qua khd ndng phdn hiiy dung djch metylen xanh dudi biic xg din compact Nguyen Vdn Hung vd cgngsu ddng nhi?t hap phy-gidi hip nito tgi 77 K tren thiet bj Micromeritics (My) Gid tri ndng lupng lien kit vd trgng thdi oxi hda ciia cdc nguyen to dude ghi phi XPS tren mdy S-Prob!e TM2803 dudi ngudn phdt xg tia X AIK,, vdi VLing ndng lupng qua tii 0-1000 eV PHUONG PHAP NGHIEN CllRj KfiT QUA VA T H A O L U A N 2.1 Th^c nghiem 3.1 Anh hirdng ciia nSng dp ure Cac hda chat dupe sCr dyng thyc nghiem deu d dgng tinh khiet md khdng can chi hda bo sung Hda tan 4,0 gam TiOS04 vdo 50 ml dung djch H2SO4 0,018 M Cho tilp lupng urfi vd mu6i amoni vonframat xdc djnh vdo dung djch TiOS04 vira thu dupe, khudy dlu khodng 15 phiit Dung djch h6n hpp dupe pha lodng bdng nude cit hai lin din 220 ml vd tiln hdnh thuy phdn d 100°C gid dudi dilu ki§n khuiy trpn mgnh, diu dupe huyen phu Huyin phii dupe rua vdi lan bdng nude cit vd sau la etanol cho din khdng cdn phdt hif n ion S04^" nude nia (thu vdi dung djch BaCb 0,2 M) Sdy khd huyIn phii d 110°C 24 gid vd nung d 500''C gid, thu dupe sdn phdm bdt W-Ti02 Mdu TiOi khdng biln tinh dupe dilu chi tucmg tu nhung khdng cd su bd lupng mudi amoni vonframat Hoat tinh QXT ciia cdc mdu dupe thCr bdng each tron 0,15 g bpt sdn phdm vdi 200 ml dung dich metylen xanh cd ndng dp 10 mg/l, khudy trpn hdn hpp 30 phut bdng toi dl cdn bdng hap phy-gidi hap trudc chilu xg bdng den compact Golstar 40 W vdi viing budc sdng ddc trung la 435 nm, 545 nm vd 610 nm, thdi gian chilu xa gid Hieu sudt phdn iing QXT dupe xdc dinh bdng cdch so sanh dp hdp thu quang (Abs) ciia dich trudc vd sau phdn ling d eye dai hap thy X = 663 nm De khdo sdt dnh hudng ciia nong dp ur6, lupng ure dupe cho vdo dung dich thiiy phan cho iing vdi cdc nong dp ure khdc nhau: 0,30, 0,45, 0,60, 0,75 vd 0,90 M Cdc mlu dupe ki hi?u tucmg iing tir TPWU4 din TPWU12 Gidn dh XRD ciia cdc mdu d cdc n6ng dd ur€ khac dupe dua d hinh Gid trj kfch thudc hgt trung binh vd hi?u suit phan hdy quang ciia ch6ng dupe trinh bdy bdng I 2.2 Cac phinmg phdp xac dinh Gian dd XRD ciia b^t Ti02 dupe ghi tren nhilu xg kl tia X D8 Advance Brucker (Diic) vdi tia CuK^ c6 X = 0,154056 nm, nhi?t dp ghi 25°C, gdc 29: 10 -70°, tdc dp quet 0,037s Kich thudc hgt trung binh dugc xac djnh dya vdo pic d§c trung tren gidn XRD theo cong thiic Scherrer Phd UV-VIs ciia san phdm dupe ghi tren mdy JASCO-V670 (Nhat Bdn), budc sdng qu6t tir 250-i-800 nm, tdc dO quet 400 nm/phut Cdc anh TEM ciia sdn phdm bOt Ti02 dupe chyp tr6n kinh hiln vi di?n tu truyin qua JEMlOlO (JEOL-Nhgt Ban) cd he so phdng dgi M = x50 den xdOO.OOO, dp phdn giai = A, di6n ap gia toe U = 40 din 100 kV Di^n tich bl m#t BET dupe xdc dinh tir dudng Anatase Analase 1.TPW4 2.TPW6 3.TPW8 4.TPW10 5.TPW12 j! ,, , -.u w|Lwv/L«-.^2 -J JL-/UJ\.I 4D SO 2-Theta-Scale Hinh 1: Gian dd XRD ciia cac mdu W-Ti02 d ndng dp ure khac Bdng Anh hudng cua ndng dp UT% din kich thudc hat trung binh va hieu suit phan hiiy quang cua cdc mdu W-Ti02 Kf hi?u mlu N6ng ure, M r, nm H, TPWU4 TPWU6 TPWU8 TPWUlO TPWU12 0,30 0,45 0,60 0,75 0,90 15,7 14,9 13,8 14,2 15,5 87,73 92,54 97,98 94,21 90,40 % Til hinh va bang cho thay, tat ca cac mlu d6u a dang don pha anata vdri dinh pic dac tnmg img vdi goc 26 ~ 25,3° Khi tang din n6ng dp ure tir 0,30 d6n 0,60 M thi kich thuoc hat trung binh giam va dat gia trj cue tieu img voi mlu c6 n6ng dp ui€ la 0,60 M TCHH, T 50(4), 2012 Anh hudng ciia W(VL) din cdu triic Neu tiep tyc tdng n6ng dp urfi > 0,60 M thi kich thudc hgt trung binh tdng Dilu ndy cd thi gidi thfch, ure cd nhdm -NH^ nen cd thi xem nd nhu Id chit hogt dpng bl m^t M$t khdc, su6t qud trinh phan hiiy cdc ion NH4"' dupe tgo tir tir vd phdn b6 dong deu todn b$ the tich ciia dung djch n6n trdnh dupe hi?n tupng kit tiia vCing Do dd, tflng dan ning dp urS kich thudc hgt trung binh gidm Tuy nhien, ning dp ure qud Idn din den sy thiiy phdn mgnh ciia cdc cation kim logi nen Idm tdng kich thudc hgt Nhmig nhin chung, vdt li§u W-Ti02 dilu chi dupe cd kich thudc hgt khd bi (khodng 14 den 16 nm) Bdng cdn cho thiy sy phii hpp giOa quv lugt bien dii kich thudc hgt trung binh vd hi^u suit phan hiiy quang Mdu W-TiO; img vdi ning dp urS 0,6 M cd kich thudc hgt trung binh hi nhit vd cho hi$u suit phdn buy quang dung djch metylen xanh Idn nhit sy [5] gidi thich, cd sy tuong ding vl bdn kfnh git^a ion W(VI) vd Ti(IV) nSn W(VI) dl ddng thay till Ti(iV) ciu triic mgng ludi Ti02 de hinh thdnh dung djch rdn WxTi|.x02 Thdnh phin, thdng si mgng ludi, kich thudc hgt trung binh vd hi^u sudt phdn hiiy quang cCia cdc mlu theo ty I? mol W/T1O2 khdc dupe trinh bdy bdng Tir bdng cho thiy, tdng din t;J' I? mol wn"i02 kich thudc hgt trung binh gidm Dilu ndy chimg td, sy cd mdt ciia W(VI) mgng ludi TiC^ da ire chi sy phdt triln hgt vd Idm gidm ddng kl kfch thudc hgt ciia cdc mlu W-TiOj so vdi mlu TiOj khong biln tfnh Quy lu^t gidm din kfch thudc hgt 1102 tdng din n6ng dd W(V1) cung dd dupe cdng bl cdc cdng trinh nghien cim [5,6] Bdng 2: Thdnh phin, thdng so mgng ludi, kfch thudc hgt trung binh vd hi^u suat phan hiiy quang ciia cdc mlu d ty I? mol W/Ti02 khdc 3.2 Anh hudng cua ly 1$ mol W/TiOi Ndng dp ion biln tinh Id m0t nhChig ylu tl quyet dinh den cau triic vd hogt tinh QXT ciia Ti02 De khao sdt dnh hudng ciia nong dp W(VI), lupng amoni vonframat dupe cho vdo dung djch thCiy phdn cho ling vdi cdc ty I? mol W/TiO: khdc nhau: 0, 0,05, 0,1, 0,15, 0,2 vd 0,25% Cdc mau dupe kl hi?u tuong img tir TPWO din TPW0,25 Gidn XRD cua chiing dupe dua d hinh —1.TPW0 2.TPW0,05 3.TPW0,10 4.TPW0.15 5.TPW0,2O 6.TPW0,25 Anatase dlr~ArTt J L \3 2-Theta-Scale Hinh 2- Gidn dl XRD ciia cdc mdu d ty 1? mol W/TiOj khdc Tir hinh cho thay, tit cd cdc mau deu d dgng don pha anata Dinh pic ddc trung cho pha anata ciia cac mdu W/Ti02 ling vdi gdc 20 -25,3° vd mdu Ti02 khdng biln tinh iing vdi gdc 29 -25,32° Kit qud ndy chiing td cac vdt li?u W-TiO; cd kich thudc hgt trung binh hi hon so vdi mdu Ti02 khdng biln tinh Ngodi pic ddc trung cho pha anata khdng thiy xuat hi§n pic cho pha WO3 hodc pha Ig ndo khdc mdu Dilu ndy cd thi W(VI) da tham gia vdo cau true mgng ludi ciia Ti02 Haiyan Song vd cdc c^ng Ki hi$u mau TPWO TPW0,05 TPWO.IO TPWO, 15 TPW0,20 TPW0,25 Thong so Tyl? mol m^ng ludi W^iO,, a = b, c, % 0,05 0,10 0,15 0,20 0,25 A A 3,782 3,784 3,785 3,787 3,790 3,787 9,504 9,507 9,505 9,511 9,502 9,509 r, nm H, 19,4 14,9 13,7 11,8 11,4 10,6 60,43 84,70 99,4« 93,55 89,70 85,13 % Tir bdng cho thiy, cd sy sai khdc thdng si mgng ludi giOa cdc mau W/TiOj so vdi mlu Ti02 khdng bien tfnh Kit qud chiing td, W(VI) dd tham gia vdo cau tnic mgng ludi TiO: Sy sai khdc ndy theo chilu hudng cdc mdu W-Ti02 cd cdc hdng so mgng a va c Idn hon so vdi mlu Ti02 khdng bien tinh tdng din ty 1? mol W/TiOi Dilu ndy Leo'nRamos [7] cho rdng, tuong tdc ddy giiia cdc ion W(VI) mgng ludi TiOj Bdng cdn cho thiy, tdng dan ty 1^ mol W/TiOi hi$u suit phan buy quang tdng vd dgt gia hi eye dgi d mlu cd ty l§ mol W/TiOz 0,1% NIU tilp tyc tdng ty 1? ndy > 0,1% thi hi$u suat phdn bdy quang giam Kit qua ndy cung phii hpp vdi kit qud dd cdng bo d cdng trinh [8], dilu chi vgt li§u W/Ti02 bdng phuong phdp thiiy phdn dung djch TiCl4 vdi cdc ty 1? mol W/Ti02 khdc nhau: 0,1, 0,5, 1,0 vd 10% Lee [8] nh§n thiy niu tdng ty 1? mol Wrri02 > 0,1 % thi hi?u suit phdn hiiy quang gidnu j Theo H Tian [9] thi W(VI) mgng ludi TiOz d l ddng bi khii xuong W(V), cdc electron bj kich thlf^ quang viing ddn cCia Ti02 cd thi dupe nhan bdi W(VI) theo phuong trinh (1): W(VI) + e ( - ^ j ^ ^ W ( V ) (1) Trong trudng hpp ndy, biln tfnh W(VI) giiip bdy TCHH, T 50(4), 2012 cSc di§n tii quang sinh nhIm giim sv tii kit hpp gitta cic di|n tir va la nen ting cuimg host tinh QXT Tuy nhien, bien tinh W(VI) n6ng dp qui cao, n6 sg_hoat dpng nhu cic tam tai kit hprp cua c$p electron-16 tr6ng (lim giam hi$u suit phan hiiy quang) theo hai phuong trinh (2) vi (3): W(VI) + e,>,au->W(V) V'Cih • W(V1) Nguyen Vdn Hung vd cdng su tuong img d hinh vi Kit qua tinh toin cho thiy m^au img vdi ty Ip W/TiOi 0,1% cd nSng lupng vijng cam (-2,25-2,88 eV) h6 hon so vdi mlu TiO; khdng bien tinh (-2,93 eV) Nhu vjy, s(r hipn dipn cua W(VI) mang ludi TiOi da thu hpp ding ki ning lupng vimg elm ciia n6 (2) Ph6 UV-VIS cua cic mlu theo tj 1? mol W/TiOj khic dupe dua a hinh Tir hlnh cho thiy, tit ci cic mlu W-Ti02 diu c6 dO hip thy quang vimg anh sing nhin thiy cao hon so v6i mlu TiO: IdiOng biln tinh, Khi ting din ty 1^ mol WA'iO: thi dp hip thu quang vimg c6 bu6c s6ng Idioin^ 450 den 600 nm ting vi d^t gii trj hip thy ldn nhat ung vdi mlu c6 t^ Ip mol W/TiOi 0,15% Neu tiep tyc ting ty le mol W/TiOj > 0,15% thi dp hip thy quang cd phan giim Ph6 UV-VIS va m6 hinh tinh toin gii trj ning lupng viing elm cua mlu TiO: khdng bien tinh vi mlu W-Ti02 d ty Ip mol W/TiOi 0,1% dupe dua Hmh 3: Pho UV-VIS cua cac mlu o ty Ip mol W/Ti02 khic MnR dlfdc bie'nllnh ^ — M i u Hat vdi ly Ifi muJ W/T1O2 = «,i % / 423 nm = 1240/423 = 2,93 eV 1 = 430 nm g = 1240/430 = 2,88 eV 1^ / ^=5S0nni Eg = 1240/5SO = 2,25 eV 500 Birdc song, nm Hmh 4: Phd UV-VIS ciia mlu TiOj khdng dupe biin tinh W(V1) Anh TEM ciia mdu Ti02 khdng biln tfnh vd mlu W-TiOi dty le mol W/TiOj 0,1% dupe duara.tuong 6ng d hinh vd Tii cdc dnh TEM cho thiy, mlu W-TiOj d ty le mol WA'i02 0,1 % cd kfch thudc hgt b^ (~ 13-14 nm) vd phan bo dong dlu hon so vdi mlu Tp2 khdng biln tinh (~19-20 nm) Mlu Ti02 khdng biln tfnh vd mlu W-Ti02 d ty 1| mol WA'i02 0,1% dupe tiln hdnh ghi ddng nhi$t hip phu - gidi hip phy N2 (BET) Ket qud BET cho thdy, mlu W-Ti02 d t j 1$ mol W/TiOj 0,1 % cd di?n tfch bl mat (67,3 m^/g) ldn hon so vdi mlu TiO: khfing biln tfnh (43,5 mVg) Nhu vdy, sy hi?n di$n ciia W(VI) mgng ludi Ti02 da cdi thi^n dang kl di^n tfch be mgt ciia nd , Mdu Ti02 khdng biln tfnh vd mlu W-Ti02 d ty 1| mol V/TTiOi 0,1% dupe chiing tdi tiln hdnh ghi 600 700 BOD BiTdc s6ng, nm Hinh 5: Phd UV-VIS ciia mdu W-Ti02 d tylemol W/TiO2 0,l% phd XPS nham xdc dinh ndng lupng lien ket (BE) vd trang thai oxi hda ciia cdc nguySn td cd mdt mdu Gidn dl XPS ciia cac mau ndy dupe dua d hinh Tir hinh cho thi);, mdu Ti02 kh6ng biln tinh cd mdt cac nguyen td Ti, O, N vd C, Mdu W-Ti02 ngodi sy cd mat ciia nhimg nguySn to ndy cdn c6 them nguy8n td W Mdu Ti02 khdng biln tinh vd mlu W-Ti02 cd pic C s iing vdi cac gid trj BE tuong img Id 285,7 vd 285,4 eV Kit qua cd thi Id su hifu chinh bdi phd trgng thai C-C ciia chinh dyng cu XPS Pic N Is ciia mdu Ti02 khdng biln tfnh vd mdu W-Ti02 cd gia trj BE img vdi 400,7 vd 400,8 eV Sir xuit hien pic N Is cd th^ Id N cdn ldn lgi mdu ma chua the logi bo hit sau qua trinh thiiy phan /inh hudng ciia W(VI) ten cdu triici TCllH.T ."^0(4) 2012 Hlnh 7: Anh TEM cua mlu Wrt'lO: tyl?molWn-iO2 0,l% Hmh 6: Anh TEM ciia mlu TiOj khdng dupe bien tinh W(V1) i " |til.t¥l,u