Nguyen Xuan Huan.pdf

  • View
    213

  • Download
    0

Embed Size (px)

Transcript

  • 1

    Phng php ch to vt liu Fe0 nano c th bo qun iu kin thng v ng dng

    kt hp x l nitrat v pht pht trong nc

    Nguyn Xun Hun, L c

    Khoa Mi trng, Trng i hc Khoa hc T nhin

    334 Nguyn Tri, Thanh Xun, H Ni

    Tm tt

    Nghin cu ny gii thiu phng php ch to vt liu Fe0 nano phn tn tt v c th bo

    qun trong bnh ht m iu kin thng. Polyacrylamid (PAA) l mt cht khng c c s

    dng lm cht phn tn trong ch to Fe0 nano. Khi thm PAA n gp phn lm tng mnh hot ng

    ha hc, tnh n nh v kh nng linh ng ca b mt vt liu. N lm (1) gim kch thc ht Fe0

    nano t 200 nm xung 16,7 nm v s hp ph ca PAA trn b mt vt liu c biu hin qua chp

    nh TEM; (2) din tch b mt ca vt liu kh ln (60 m2/g), c th hin qua chp BET; (3) Chp

    nhiu x tia X ch ra s tn ti ca vt liu va ch to ch yu l Fe0 nano; (4) Cc ht st nano

    to thnh khng lin kt vi nhau thnh m m tch ri nhau, c th hin qu chp nh SEM.

    ng dng vt liu Fe0 nano (nZVI) trong x l nhim mi trng l mt hng quan tm mi

    ca nhiu nh khoa hc trn th gii. Bo co ny nghin cu ng dng vt liu Fe0 nano bo qun

    iu kin thng x l kt hp nitrat v pht pht trong nc. Kt qu nghin cu cho thy hiu

    qu x l nitrat v pht pht bi Fe0 nano tng dn theo thi gian v tng nhanh nht 10 pht u

    tin. Hiu sut x l sau 60 pht t 93,41% i vi nitrat v 86,17% i vi pht pht. Hiu qu x l

    nitrat v pht pht bng Fe0 nano gim dn khi pH tng. Ti pH = 2 hiu sut x l t gi tr cao nht

    l 86,17% i vi nitrat v 84,9% i vi pht pht. Khi kt hp x l nitrat v pht pht th hiu qu

    x l gim khng nhiu so vi x l ring nitrat v pht pht. V vy vt liu Fe0 nano c th s dng

    x l ng thi c nitrat v pht pht m khng lm nh hng nhiu n hiu qu x l.

    T kha: Ch to, vt liu, st nano, kt hp, x l, nitrat, pht pht.

    1. M u1

    Vt liu nano l vt liu trong t nht mt chiu c kch thc nano mt c th tn ti 3

    trng thi rn, lng v kh. Vt liu st kch thc nano c th c tng hp t nhiu phng php

    nh phng php nghin, vi nh tng, in ha, kh bohirua,... Trong , ph bin nht l

    phng php kh bohirua [1]. tng c bn ca phng php kh bohirua (kh pha lng) l

    thm mt cht kh mnh vo mt dung dch ion kim loi kh n thnh cc ht kim loi c ha tr 0

    v kch thc nano. Phng php ny c s dng ch to cc ht st kch thc nano

    trong nghin cu ca Glavee v cc cng s u nm 1995. Cht kh c s dng ph bin nht l

    1 Tc gi lin h. T: 0983665756 E-mail: huannx@hus.edu.vn

    http://vi.wikipedia.org/wiki/V%c3%a1%c2%ba%c2%adt_li%c3%a1

  • 2

    NaBH4. Cc dung dch s dng l st (III) clorua (FeCl3.6H2O) v st (II) sunfat (FeSO4.7H2O) c

    th hin qua cc phng trnh sau:

    4Fe3+ + 3BH4- +9H2O 4Fe

    0 + 3H2BO3- +12H+ +6H2

    Fe2+ + BH4- + 9H2O Fe

    0 + H2BO43- + 12H+ +6H2

    Phng php ny to ra Fe0 nano c th bo qun trong iu kin thng, phng php n

    gin v hiu sut iu ch cao nn c ng dng nhiu trong iu ch st nano. Tuy nhin, mi tc

    gi khc nhau u c nhng iu kin ch to, lm kh, bo qun khc nhau v kt qu thu c

    cng l khc nhau: Theo Nazli Efecan, Talal Shahwan, Ahmet E.Eroglu, Ingo Lieberwirth ha tan

    FeCl2.4H2O trong dung dch ethanol v nc ct theo t l th tch 4:1, sau dng mt lng d

    NaBH4 kh. S dng bnh ht chn khng lc phn ht st, ra sn phm bng ethanol 99% t

    nht 3 ln v lm kh trong l sy 750C qua m. Mara E. Morgada, Ivana K. Levy, Vanesa

    Salomone, Silvia S. Faras, Gerardo Lpez, Marta I. Litter cng lm tng t nhng s dng my li

    tm vi tc 2.500 vng/pht trong 20 pht thu ht Fe0 nano. Mu c lm kh trong l sy

    400C trong 24h v c bo qun trong kh N2. Heesu Park, Yong - Min Park, Kyoung - Min Yoo and

    Sang - Hyup Lee th cc dung dch s dng iu ch Fe0 nano u c ui xi bng kh argon

    sau loi b dung dch v ra cht c tng hp bng nc ion ha v bng ethanol ngn

    cn s oxy ha v lm kh trong chn khng. Choi, Hee- chul s dng NaBH4 kh FeSO4.7H2O

    ha tan trong dung dch ethanol 30% vi t l khi lng ca NaBH4/ FeSO4.7H2O l 1/10. Sn phm

    c ra bng ethanol, sau ly tm v phi ngoi khng kh [2]). Trong nghin cu ny chng ti

    ch to vt liu Fe0 nano bng phng php kh st (II) sunpht bi bohirua vi t l khi lng

    ca NaBH4/ FeSO4.7H2O l 1/2, c s dng cht phn tn l polyacrylamid (PAA) v nghin cu nh

    hng ca mt s yu t ti qu trnh ch to vt liu. Phn tch mt s c tnh ca vt liu ch to.

    Tnh hnh nhim nitrat v pht pht trong h thng nc mt v nc ngm hin ang ngy

    cng nghim trng do nh hng ca nc thi cha qua x l t cc hot ng sn xut nng

    nghip, cng nghip v sinh hot. Nc b nhim nitrat v pht pht c th gy hi cho sc khe

    ca con ngi khi s dng cho mc ch n ung hay sinh hot. Ngoi ra, hm lng nitrat v pht

    pht qu cao trong nc cn gy ra hin tng ph dng ngun nc, tc ng xu ti h thy

    sinh vt cng nh cnh quan, gy mi hi thi nh hng n mc ch s dng ca cc thy vc. V

    vy, vic nghin cu cc gii php cng ngh x l ngun nc b nhim nitrat, pht pht hay

    ngun nc b ph dng ang l mi quan tm ca nhiu nh nghin cu. Trong nhng nm gn

    y, cng ngh s dng Fe0 nano c nhiu tnh nng u vit trong x l nhim mi trng nh: x

    l nc thi c cha cc hp cht hu c kh phn hu, kim loi nng, ho cht bo v thc vt.

    c bit l Fe0 nano va c tnh kh, va c kh nng hp ph b mt nn n c kh nng x l

    ng thi nitrat v pht pht trong nc.

    2. Nguyn liu v phng php

    2.1. Nguyn liu

  • 3

    - FeSO4.7H2O

    - Bohirua (NaBH4)

    - Etanol 100 %

    - Polyacrylamid (PAA)

    - Cc mu nc t to nhim nitrat v pht pht t ha cht KH2PO4, KNO3 loi tinh khit ha

    hc c nng l 50 mg N-NO3-/L v 50 mg P-PO4

    3-/L.

    2.2. Ni dung v phng php nghin cu

    2.2.1. Nghin cu nh hng ca cht phn tn PAA n kt qu ch to Fe0 nano

    B tr hai th nghim ch to Fe0 nano cng cc iu kin nh nhau, trong th nghim 1

    khng s dng cht phn tn PAA v th nghim 2 c s dng cht phn tn PAA vi nng 0,01%.

    Kt qu chp nh SEM v TEM so snh.

    2.2.2. Nghin cu nh hng ca t l NaBH4 v FeSO4.7H2O n kt qu ch to Fe0 nano

    B tr hai th nghim ch to Fe0 nano cng cc iu kin nh nhau, trong th nghim 1

    s dng t l v khi lng NaBH4/FeSO4.7H2O l 1/10 theo Choi, Hee- chul v th nghim 2 s dng

    t l v khi lng NaBH4/FeSO4.7H2O l . Kt qu c so snh vi cc nghin cu cng b.

    2.2.3. Nghin cu nh hng ca vic s dng cn pha mui st n kt qu ch to Fe0 nano

    B tr hai th nghim ch to Fe0 nano cng cc iu kin nh nhau, trong th nghim 1

    s dng cn 30% ha tan mui st theo Choi, Hee- chul v th nghim 2 mui st c ha tan

    trong nc sau b sung cn t nng cn l 30%. So snh cc kt qu thu c v la

    chn gii php u vit.

    2.2.4. Nghin cu cc phng php bo qun Fe0 nano

    B tr th nghim ch to Fe0 nano v bo qun trong bnh ht m, kt qu c chp nh

    SEM, TEM v so snh vi cc kt qu nghin cu c cng b.

    2.2.5. Nghin cu mt s c im ca vt liu Fe0 nano

    Sau khi la chn c cc iu kin tt nht iu ch vt liu Fe0 nano, sn phm to

    thnh c kim tra c tnh thng qua phng php nhiu x tia X (XRD), chp nh Scaning

    electron microscopy (SEM), nh Transmission electron microscopy (TEM) v phn tch din tch b

    mt theo phng php Brunauer Emmett Teillor (BET).

    2.2.5. Nghin cu hiu qu x l ring nitrat bng vt liu Fe0 nano

    - B tr th nghim nh hng ca thi gian n hiu qu x l ring nitrat

    Ht 50mL dung dch nitrat c nng 50 mg N-NO3-/L vo 4 bnh tam gic c dung tch 100

    mL, iu chnh v pH = 2. Cn chnh xc 0,05g Fe0 nano (tng ng nng Fe0 nano/ dung dch

    cn x l l 1 g/L) cho ln lt vo 4 bnh tam gic trn. Lc trn my lc vi tc 250 vng/pht

    trong cc khong thi gian khc nhau l: 10, 20, 40 v 60 pht. Ly tm vi tc 2.500 vng/pht v

    xc nh nng nitrat cn li trong dung dch.

    - B tr th nghim nh hng ca pH n hiu qu x l ring nitrat

  • 4

    Ht 50 mL dung dch nitrat c nng 50 mg N-NO3-/L vo 4 bnh tam gic c dung tch 100 mL.

    iu chnh gi tr pH ca cc dung dch trong bnh tam gic v 2, 4, 6 v 8 bng dung dch H2SO4 v

    NaOH tiu chun 0,01N. B sung vo mi bnh tam gic trn 0,05g Fe0 nano (tng ng nng Fe0

    nano/ dung dch cn x l l 1 g/L). Lc trn my lc vi tc 250 vng/pht trong thi gian 40 pht.

    Ly tm vi tc 2.500 vng/pht v xc nh nng nitrat cn li trong dung dch.

    2.2.6. Nghin cu hiu qu x l ring pht pht bng vt liu Fe0 nano

    B tr th nghim nh hng ca thi gian v pH n hiu qu x l ring pht pht tng t

    nh b tr th nghim nh hng ca thi gian v pH n hiu qu x l ring nitrat nhng vi dung

    dch pht pht c nng ban u l 50 mg P-PO43-/L. Sau xc nh nng pht pht cn li

    trong dung dch.

    2.2.7. Nghin cu kt hp x l nitrat v pht pht bng vt liu Fe0 nano

    B tr th nghim nh hng ca thi gian v pH n hiu qu x l kt hp nitrat v pht pht

    tng t nh b tr th nghim nh hng ca thi gian v pH n hiu qu x l ring nitrat v pht

    pht nhng vi dung dch hn hp nitrat v pht pht c nng ban u l 50 mg N-NO3-/L v 50

    mg P-PO43-/L. Sau xc nh nng nitrat v pht pht cn li trong dung dch.

    Phn tch nng nitrat v pht pht cn li sau khi x l bng phng php so mu quang in trn

    my UV- VIS754 ti bc sng = 430nm v = 710nm.

    3. Kt qu v tho lun

    T cc phng php iu ch Fe0 nano ca cc tc gi nu trn, chng ti s dng

    phng php iu ch Fe0 nano bng cch dng NaBH4 kh mui st (II) FeSO4.7H2O pha trong cn

    vi tc cho cht kh l 3 n 7 ml/pht. Nghin cu mt s yu t c nh hng n qu trnh

    iu ch v bo qun sn phm.

    3.1. nh hng ca cht phn tn PAA n hiu qu ch to Fe0 nano

    Khi khng s dng cht phn tn th sn phm thu c sau phn ng to thnh 2 lp: 1 lp

    trn v 1 lp di tch bit. Lp di c mu en, ht bm cht vo que khuy t v c kch

    thc ln hn so vi lp trn (hnh 1). Ht st c hnh cu hoc hnh dt v kch thc khong t 50

    - 200nm. Tuy nhin gia cc ht khng c s phn bit r rng v kch thc phn b khng u. Lp

    trn c mu xanh en, so vi lp di th kch thc ht nh, mn hn (hnh 2). Ht st to thnh

    lin kt vi nhau thnh hnh que v bm vo nhau thnh tng m ln, kch thc ht khong 40-

    100nm.

  • 5

    Khi c s dng cht