DAI HOC QUOC
GIA
HA
NOI
TRirONG DAI
HOC
KHOA
HOC
TV NHIEN
NGHIEN
ClTU
XLT
LY
CAC
HOP CHAT
UlfU
CO
KHO PHAN HTJY
SINH
HOC TRONG
NlTOC
THAI
BANG CAC
PHUONG
PHAP OXY HOA CAP TIEN
MA
SO:
QT-06-42
CHU
TRI:
ThS.
thai bang cac
phuong
phap oxy hoa cap tien.
Tieng
Anh\
Investigation for treatment of refractory organic compounds in the
wastwater by advanced oxidation processes.
2.
Chu
nhiem
de tai:
Hoc vi: ThS. GVC
Tel:
8213847/0904700062
Cac can bo tham gia de tai:
-
Nguyen Thi Ha
- Luu Minh Loan
- Phan Mai Linh
- Nguyen Quang Huy
- Nguyen Thi Xuan
Dong Kim Loan
Dan vi
cong
tac: Khoa Moi truong
TS.
GV
ThS.
CBNC
CN.
CAC CAN
BO
THAM
GIA
DE TAI
- Nguyen
Thj
Ha
- Luu Minh Loan
- Nguyen Thj Mai Linh
- Nguyen Quang Huy
-Nguyen thi Xuan
TS.
GV
ThS.
CBNC
CN.
CBNC
CN.
CBNC
CN.
CBNC
- Mot so sinh vien Khoa Moi truong va can bo So KHCN&MT Ha Tay,
Thai nguyen.
MUC TIEU
NGHIEN
CUU:
- Phan
loai
cac chat
DUNG
NGHIEN CUU:
- Thu thap tai lieu
- Nghien cuu, xu ly
4-clorophenol
bang tac nhan Fenton
- Nghien cuu che tao xuc tac hat
TiO?
tren mot so chat mang
- Nghien cuu
ch^
tao mang xuc tac quang hoa
Ti02
tren mot so nen
(xuoTig/phoi)
khac nhau.
- Nghien
curu
xu
ly
nuoc thai det nhuom bang xuc tac quang hoa
TiO?
/UV
CAC KET QUA DAT
DlSOC:
- Hai
thiSt
bi nghien cuu da
dugc
thiet ke va lap dat phuc vu cho cac nghien
PHI CUA DE TAI:
De tai da thuc hien cac chi
phi
the hien tren bang duoi va da tien hanh
thanh quyet toan
voi
Phong Tai vu nha truong
truoc
ngay
31
thang
12
nam 2006.
stt
I
2
3
4
5
6
Danh muc chi
•
Dung cu, hoa chat nghien cuu
Hgp dong NCKH ve
"Nghien
cuu xu ly chat huu ca
kho phan
hiiy
sinh hgc bang tac nhan
Fenton"
114/06
114/06
114/06
119/03
109/01
1
7
8
9
4
5
-
_
_ ,
Van
phong
pham
Hoi thao-cac bao cao vien
Hoi thao-cac
dai
bieu
Quan ly phi
Tong chi phi
100.000
400.000
680.000
600.000
15.000.000
110/01
112/02
The Target of the Project:
-Classifying and studying the applied methods to treat wastewater of
concentrated and biorefractory organic compounds in Vietnam and over the
world.
-Trying several advanced oxidizing processes for treatment of refractory organic
compounds.
-Preparation of some
Ti02
photochemical catalysts for treatment refractory
organic compounds.
Abstract of the content:
-Collecting the documents.
-Investigation and treatment of
4-chlorophenol
by Fenton reagent
-Preparation of
Ti02
granulated catalysts on any support
-Preparation of thin films of
Ti02
on different solid matrixes
-Investigation for treatment of dye wastewater by
Ti02
photochemical catalysts
The results:
Science and Technology:
-Two full-scale systems were designed and installed for treatment of wastewater
by photocatalytic of the project. There is a circulating wastewater system and
ultraviolet light in there instrument.
-A set of reactor for Fenton reaction
Nghien cuu loai bo cac
hgp
chat co
clo
bang tac nhan phan ung
Fenton
16
4.1.
Xay dung thiet bi va cac dieu kien nghien cuu
16
4.2.
Ket
qua nghien cuu va thao luan
17
5.
Nghien cuu che tao xuc tac
Ti02 18
5.1.
Che tao vat lieu hat mang
Ti02
19
5.2.
Chi
tao mang
Ti02
20
6. Xu ly nuoc thai det nhuom voi cac vat lieu
xiic
tac da che tao 23
6.1.
hieu
nham loai bo cac chat 6 nhiem ben, doc hai va kho phan huy sinh hoc trong nuoc
va nuoc thai da tro thanh thach thuc voi cac nha khoa hoc. Cac qua trinh oxy hoa
cap tien (advanced oxidation processes) dang thu hut su tap trung nghien cuu cua
nhieu nha cong nghe va cac hang ban thiet
bj
xu ly moi truong vi kha nang lam
giam thieu va loai bo cac chat 6 nhiem loai nay.
De tai "Nghien
ciiu
xu ly cac
hgp
chat
hiru
co kho phan huy sinh hoc trong
nuoc thai bang cac phuong phap oxy hoa cap tien" co ma so QT - 06 - 42 dugc
thuc hien duoi su ho trg kinh phi cua Dai hoc Quoc gia Ha noi.
Xin cam on su cong tac ho trg va giup do cua Bo mon Ky thuat nuoc va
nuoc thai, Khoa Cong nghe moi truong; Bo mon Vat lieu v6 co, Khoa Cong
nghe hoa hgc Truong Dai hgc Hoa Ky thuat Praha, Cong hoa Sec.
Cam on su tao dieu kien cho lam viec, cong cu phan tich cua Phong thi
nghiem Cong nghe Moi
truong.
Bo mon Cong nghe hoa hoc, Khoa Hoa hoc
Truong Dai hgc Khoa hoc Tu nhien DHQG Ha noi.
Cam on su cong tac giup do cua Trung tam Nghien cuu, Quan trac va Mo
hinh hoa moi truong Truong Dai hgc Khoa hgc Tu nhien DHQG Ha noi.
Chu tri de tai
TS.
GVC. Dong Kim Loan
Igi
cho
sue
khoe, gay nguy hai moi truong cho ca, dong vat hoang da hoac mot cau tu
nhay cam nao do cua mot he sinh thai. Da phan
chiing
la cac hgp chat vong
thom, da vong ngung tu, cac co clo, chat mau azo Trong so nay nhieu hgp chat
la cac chat huu co tong hgp dugc phat sinh tu qua trinh san xuat va la nhung san
pham phu (chat thai) khong mong muon nhu dioxin
Noi chung, cac hgp chat
hiJu
co kho phan huy sinh hoc deu co do tan nho
trong nuoc, nhung
lai
thuong c6 mat nhieu trong nuoc tu rat nhieu nguon khac
nhau. Do kho phan huy sinh hgc, thoi gian ton luu
lau
va kha nang tich
luy
sinh
hoc cao nen chi
6
mot nong do thap da gay 6 nhiem
Ion
cho moi truong nuoc.
Chinh
vi vay, tim kiem cac bien phap de xu ly loai bo cac hgp chat nay
luon
la can thiet; song trong thuc te dang con gap nhieu kho khan ve ky thuat
hiiy
cac
clorophenol cao hon va axit
2,4-diclorophenoxy.
Hau het cac hgp chat co clo deu
rat ben vung, doc hai va ton tai lau trong moi truong.
Clorophenol ton tai trong moi truong nuoc duoi nhieu dang: hoa tan
6
trang thai tu do hoac
phiic;
hap phu
Ion
tren cac chat ran lo lung, cac tram tich
hoac nam trong cac mo sinh hoc.
Cac clorophenol co the hap thu vao co the qua
duong
ho hap o dang hoi,
suong; qua da hoac qua duong tieu hoa. 4-clorophenol ciing gay ra nhung bien
doi ve mat sinh hoc doi voi dong vat, anh huong den qua trinh sinh san. 0 nong
do cao pha
hiiy
gan, than, da, kich thich da day. Tat ca cac clorophenol deu co
doc tinh cao voi tao va hau het cac thuc vat
thiiy
sinh. Ca va cac sinh vat
thiiy
sinh hap thu clorophenol qua mang, da va thanh rugt.
Cue
moi truong Lien bang
My (EPA) quy dinh nong do
het hoac khong gan mau vao sgi ma tao ra. Cac thuoc nhuom
khi nhuom co muc do gan mau khac nhau. Ty
le
mau gan vao xo sgi nam trong
khoang 50-98%, phan con lai se di vao nuoc thai lam cho do mau
ciia
nuoc thai
det nhuom luon cao. Thuoc nhuom dugc xep vao doc to nhom 1 va
2,
2.1.3.
Hoa chat trong cong nghiep duoc pham
Nhieu loai hoa chat dung trong cong nghiep dugc pham la nhung
hydrocacbon thom va khong thom co dinh cac nhom chuc va di nguyen to khac
nhau
CO
tac dung dieu tri benh. Cac hoa chat nay da phan la nhung chat co kha
nang sat trung manh, nen rat doc voi he vi sinh vat noi chung va cac vi sinh vat
trong he
xii
ly nuoc thai noi rieng.
Vi
du Woltaren hay con goi la diclophenac
[2-(2,6-dicloroanilino)phenylaxetat natri] la mot loai thuoc giam dau, chong
viem rat pho bien
diing
vao hang dau
ciia
25 loai dugc pham su dung nhieu nhat
tren the gioi va Viet nam, do do du lugng trong moi truong la dang ke. Tuy
nhien voi cong nghe xu ly nuoc hien nay, nhieu cong trinh nghien cuu da cho
hydrocacbon dau mo, cac hydrocacbon da clo hoa dugc su dung lam dung moi
va cac chat lam sach cong nghiep, cac hoa chat quoc phong nhu TNT, RDX va
HMX. Trong nhieu truong hgp hydrocacbon da clo hoa ben doi voi phan
hiiy
bang sinh hgc, nhung lai dugc
xii
ly mot
each
hieu qua nho tac dung
ciia
tia
tii
ngoai khi co mat chat oxi hoa. Dien hinh la cac hgp chat huu co bi oxi hoa de
dang
6
cac vi tri noi doi (TCE, PCE va vinylclorua) cung nhu cac hgp chat thom
(toluene, benzene,
xylen
va phenol) bi phan
hiiy
mot
each
nhanh chong bang cac
qua trinh oxi hoa/UV.
2.2.
Cac
phuang
phap xu ly
thuang
ap dung
nhu goc OH hoac/va be mat trong
dien tu
(h"^) ciia
chat
xiic
tac, nen c6 kha nang phan huy cac chat
hiiu
co ben.
-Qua trinh oxy hoa xay ra duoi cac dang phan
ling
day chuyen, nen khong
tuan theo phuong trinh ty lugng ma thuang chi can 1 lugng hoa chat nho hon
lugng tinh toan ly thuyet cung co the oxy hoa hoan toan
1
mot lugng chat
hiiu
co
xac dinh. Do do AOPs con co uu diem la tiet kiem hoa chat.
-Co kha nang oxy hoa hoan toan cac chat
hij'u
co den
CO2
va
H2O
trong
hau het cac truong hgp. Vi the khong tao san pham thu cap doc va cung co the
dugc
sii"
dung nhu qua trinh tien xu
ly
hai ra
khoi cac nguon nuoc mat ciing nhu nuoc thai.
Ngay nay cac qua trinh oxy hoa cap tien (AOPs) da phat trien theo cac ky
thuat tien tien khac nhau va dugc ggi la cac ky thuat oxy hoa cap tien (AOTs)
theo mot trong hai con duong
[15]
3.
/. Oxy hoa
uat
(wet air oxidation
-WAO)\
co kha nang oxy hoa cac hgp
chat
hiiu
co hoac v6 co trong pha nuoc bang oxy khong khi o dieu kien nhiet do
va ap suat cao. Nhiet do thuong o khoang
150-300^'C
va ap suat tu > 1 - 20 atm
thi hieu qua loai bo COD va mau co the
len
toi tu 65-90%. Cac chat co the xu ly
bang oxy hoa uot thuong la cac chat beo, cac hgp chat vong chua goc axit beo
(ma khong chua cac nhom
chiic
halogen) nhu phenol va anilin [8]. Phuong phap
oxy hoa uot c6 the ket hgp voi bun boat tinh de giam COD
ciia
nuoc thai giau
hiiu
CO.
cue
manh phan
hiiy
chat
hiru
co. Co hang loat cac phan
irng
dan
den viec hinh thanh cac goc hydroxyl: vi
dii
nhu cac phan
ling
cua
O3/UV (HofI
et
al.,
1997),
H2O2/UV,
Fe-7H202
(Fenton oxidation),
Fe-7H202/UV
(Goi,
2002) hay
Ti02/UV
(Arslan
etal,
2000) [16].
Nang
luc
oxy hoa cua mot so tac nhan the hien tren bang sau
H7O,
The
oxi hoa
1,31
Ti02'(h*) 1
2,35
sau:
Kha nang oxy hoa manh me cua goc OH [15]
dugc
minh hoa trong bang
/./
/
o-/
Bang
J.
2.
Hang so toe dp phan
ung
(k,
AT
S")
ciia ozon
so
vm goc
OH
Hgp chat
Chlorinated
alkenes
Phenols
O3
< 1
phiit,
su oxy hoa cac chat huu co xuat hien do su
ket hgp cac phan
li'ng
voi phan
tii*
O3
va cac phan ung voi cac goc OH [5].
Phan ung
giiJa
cac ion hydroxit voi
O3
dan den hinh thanh cac goc anion
peoxit
O2 "
va goc hydroperoxit
HO? ".
Nho phan ung
giiJa
goc anion peroxit voi
ozon, goc anion ozonit
O3
' dugc hinh thanh va phan buy ngay
tire
khac tao goc
OH theo phan
ling:
3O3
+
co the khoi mao cho chu trinh phan huy ozon sinh
ra goc hydroxyl
[10]
H2O2 >
HO2"
+ W
(3.2)
• 03
+
H02'
>
H02*
+
Oj'"
(3.3)
Phan ung tiep tuc theo con duong khong true tiep da mo ta
6
tren va cac
goc OH dugc hinh thanh. To hgp cac
buoc
phan ung khac nhau cho thay hai
phan tu ozon sinh ra hai goc hydroxyl theo phuong trinh sau
2O3 + H2O2 >
2*0H
+ 3O2
(3.4)
Paillard et al.
[15]
da chung minh rang: to hgp
H2O2/O3
sir
dung
xiic
tac dong
the va di the. Mot vai he
xiic
tac oxit kim loai va ion kim loai
(Fe203,
Al203-Me,
Mn02,
Ru/Ce02,
Ti02-Me,
Fe"
,
Fe'
,
Mn^"
) da
thiic
day dang ke su phan buy
chat, mac du co che phan ung trong hau het cac truong hgp chua sang to.
Cortes et al [5] nghien cuu kha nang oxy hoa tot cac clobenzen trong nuoc
thai su dung ion sat va mangan nhu nhiing
xiic
tac di the, cho ket luan: dung he
O3/CAT se loai dugc tong cacbon
hiju
co*
(TOC) va nhu cau oxy hoa hgc (COD)
khoi nuoc thai hieu qua
hiiy
sinh hgc
trong cot phan ung ozon hoa nhoi day GAC se hinh thanh cac goc
O*',
O2*"
va
O3
"
(chu khong phai goc OH) tren be mat than. Quy trinh nay da dugc thuong
mai hoa tu
1992
voi ozon cung cap la 1,7 kg cho viec loai
1
kg COD.
* He Fenton
Phan ung Fenton
(H2O2/
Fe"^)
rat phu hgp de loai bo mot so chat doc sinh
hgc khong chi vi cac tac nhan
sir
dung re va rat de kiem ma con la nhirng chat
sinh ra sau phan ung khong doc hai va qua trinh
xiic
tac xay ra trong he dong
th^
(Lopez
e/a/.,
2004).
7+
H2O2 ->
Fe^^
+
OH +
OH'
(3.5)
Ion Fe hinh thanh co the tiep tuc phan ung voi
H2O2
de tao goc
hydropeoxyl va chinh qua trinh nay lai tai tao ion
Fe"^.
Qua trinh hinh thanh va
tai tao nay xay ra theo cac phan ung 3.6, 3.7 va 3.8 sau;
H^
(3.6)
(3.7)
(3.8)
r
f
Cac goc hydroxyl hinh thanh (theo phan ung 3.5) se oxi hoa cac chat 6
nhiem theo cac ca che sau:
- Phan ung cong:
OH*
+
CgHft->
(OH)C6H6'
(3.9)
-Dehydrohoa:
OH'+
CH3OH-^
hoan toan cau triic
ciia
chat co the dat
dugc
bang each cung cap tia UV, ma khong can ozon hoac hydroperoxit
[15].
De dat hieu qua phan quang
O3
cao, cac den UV phai co cong suat buc xa
cue dai o 254 nm. Nhieu chat ban huu co hap thu nang
lugng
buc xa trong
khoang 200-300 nm va bi phan
hiiy
do phan quang
true
tiep hoac chuyen len
trang thai kich thich va nho the ma phan ung hon voi cac chat oxy hoa. Hien nay
cac den co buc xa
6 172
va 222 nm da dugc san xuat cho phan quang
true
tiep
nuoc,
sinh OH va goc H - rat hieu qua trong cac qua trinh oxy hoa UV [16, 17].
*03/uy
Ozon hap thu thang tia UV o 254 nm (he so tat
8254 nm =
3300
M"'.cm"')
UV/H2O2
(bang 3.3)
[9,10],
Trong thuc te, nang lugng doi hoi cho den UV trong qua trinh phan
quang
O3
0 co Wat doi ngugc voi co KW cho phan quang
H2O:.
8
Bang
3.3,
Su
hinh thanh *OH tii-phan quang O3 va
HjO:
p
—
Chat oxi hoa
H2O2
O3
£254 nm
M'Vcm"'
20
3300
So
do
H.O.
3O3
-
-—> 2 OH
phan quang true tiep bang
H2O2/UV
dan den hinh thanh OH
H2O2
+ ho
>
2
*0H
>
\
r
Dong thoi cung co mot can bang axit-bazo voi
H2O2,
hap thu tia UV
6
buoc song 254 nm.
H2O2
<^
HO2'
+
H'
ho +
H02'
> *OH +
O*"
Qua trinh
H2O2/UV
dugc su dung thanh cong de phan
hiiy
cac
H2O2
H2O2/UV
Xuc tac quang oxi hoa
Gia chat oxi boa
Cao
Cao
Trung binh
Rat thap
Gia
nanglugng
Trung binh
0
cao
Trung
binh
> cao
Neu su phan quang cac chat 6 nhiem khong phai la yeu to chinh thi
O3/H2O2
nen dugc can nhac nhu mot su thay the cac qua trinh oxi hoa quang boa.
1 r
Nang
lire
va gia ca hoat dong cho cac he UV/O3 va hoac
UV/H2O2
thay doi rat
rgng phu thuoc vao dong nuoc thai, kieu va nong do chat 6 nhiem co mat va muc
do yeu cau loai bo. Bang 3.4
6
tren so sanh gia ca boat dong
ciia
(3.15)
Ro rang la phan ung kieu quang-Fenton (photo-Fenton type) dua chu yeu
vao tia UV de bat dau sinh OH, neu muon cac chat 6 nhiem hiiu co bj khoang
hoa hoan toan voi cac tia
UVA^IS
[11].
Vi du: mot so chat diet co va tru sau co
the bi khoang boa hoan toan nho qua trinh quang-Fenton. Hieu qua tang len cua
cac tac nhan Fenton/kieu Fenton voi tia
UV/VIS
dugc cho la:
+Khu quang ion
Fe'^
: buc xa cua ion
Fe"^
(va hoac Fe(0H)3 sinh ra
ion Fe theo phan ung
(4.15);
ion Fe da sinh ra tiep tuc phan ung voi
H2O2
sinh
ra mot goc *0H thu 2 va ion
Fe^""
roi chu trinh lai tiep tuc.
+Su
dung hieu qua lugng tu anh sang: pho hap thu cua
H2O2
khong
vugt qua buoc song 300 nm va co he so tat thap ngoai
viing
co
the tao ra kha nang oxi hoa hoac khu hoa. 0 tren be mat
ciia
cac hat
Ti02,
nhiing
phAn
tu nay co the phan ung voi cac loai da hap thu tren do (chang han voi
O2
la
chat
nhan e (A) va OH*,
RCOO"
la
ch^t
cho e (D) )
[15,
16].
Qua trinh nay co
th^
dugc tom
tSt
nhu sau: hv
+
(SC)
^
e'
+
h*;
e"
Ti02,
6
ca 2 dang anatase va rutile la mot trong
nhiJng
oxit kim loai dugc
su dung rgng rai nhat trong cong nghiep. Chi so phan xa cao
ciia
no trong vung
anh sang nhin thay cho phep tao ra nhung mang mong va boi the no dugc
sir
dung nhu mot pigment. Mat khac, no cung dugc su dung nhu mot chat mang
xiic
tac hoac nhu mot
xiic
tac va tu quang boa
xiic
tac rat tot.
Ti02
boat dong khong
chi nhu mot chat mang
xiic
tac ma con tuong tac voi pha chat mang nhu mot
chat boat dong.
Ti02
dang anatase co bandgap nang lugng
=
3,2 ev va co the
dugc boat hoa bang
each
chieu tia UV
cac chat
hiru
co doc hai va ben tren toan the gioi dugc gianh cho PCO.
Ngay nay, PCO va cac AOP khac nhau cung dong vai tro quan trong trong cac
ky thuat xu ly nuoc uong moi
[15].
Dong gop vao viec nghien cuu cac ky thuat oxi hoa cap tien va nghien
ciiu
che tao mang
xiic
tac quang, de tai cua chiing toi dugc tien hanh voi muc dich ap
dung mot so qua trinh AOP de
xii
ly loai bo chat
hiru
co doc hai trong nuoc thai
cong nghiep o Viet nam.
3.3. Kha nang ung dung cac ky thuat oxi hoa cap tien trong
xir
ly
nw&c
va
nu'O'c
thai
Tu tong quan 0 tren cho thay van de kho khan nhat trong thuc te
ling
dung
cac AOP la
lira
chon hoac thiet ke he thong oxi boa hieu qua nhat cho chat 6
trinh
cua chat ban dan ), cac hgp chat huu co
trong nuoc thai c6 nong do tuong doi cao (> 50 ppm) trong
n^n
phuc tap thi kho
khan lai la van de nang lugng va chat oxi hoa.
K^t
qua
thii
vi
nhk
la kha nang
oxi boa nitrobenzene bang ozon ciing dat duoc
gidng
nhu oxi boa voi to hgp la
O3/H2O2
hoac
Or/UV.
Cac he UV va H2O2/UV dugc Tuhkanen nghien
ciiu
chi
ti^t
[10,
16].
Oxi
hoa quang phan naphtalen va PCP bang
biic
xa UV
t6
hgp voi
phuong phap deu nhanh, cho muc do khoang boa cao va deu co the phan buy ca
cac etylen da clohoa. Nho kha nang loai bo TCE va PCE trong khi xu ly bang O3
ma he
H2O2
/UV dugc
lira
chon cho nhiing nghien
ciiu
tiep xa hon.
Ruppert
[15]
da so sanh
sir
khoang boa 4-clorophenol voi 4 phuong phap
oxi boa cap tien khac nhau co kem theo tia UV. Duoi dieu kien chieu sang bang
den Hg ap suat cao
150
W, su phan buy TOC hieu qua theo thu tu sau:
UV/H202/Fe-^
> UV/O3 > UV/H2O2 =
UV/TiO
Su khoang hoa
UV/Ti02
va UV/H2O2 cho hieu suat kem hon trong viec
tay trang va phan
hiiy
thuoc nhugm.
Oxi hoa cap tien cac hydrocacbon da vong thom (PAHs) va mo hinh boa
toan hgc cua no da dugc Trapido nghien
ciiu
kha nang phan buy nitrophenols. Ket hgp O3 voi UV hoac voi
H2O2
thiic day
phan
hiiy
nitrophenols va lam giam tieu thu
O3
ro ret
6
nhirng gia tri pH thap. To
hgp O3/UV va
H2O2
la hieu qua nhat cho phan buy nitrophenols:
03/H202/Uv">
O3 (pH 9,5) >
O3/H2O2
> O3/UV > O3 (pH 2,5)
De dat dugc
sir
tang ve
toe
do phan
ling
va giam cung cap O3, qua trinh
O3/H2O2/UV rut khoat phai dugc
sii
dung o nhirng gia tri pH thap.
Glaze [9] da tong quat boa kinh nghiem
ciia
nhirng nghien
1,5
1,0
0
Ty le
moi
cua
photon, einstein/ OH
0
0,5
0
0,5
Ty le
moi H202/'OH
0
0,5
(H2O2
in situ)
0,5
0,5
He
O3/H2O2
cho su san sinh goc
*0H
tot, no de thich
ling
voi cac dieu
kien ozon boa hien nay va co gia xu ly tuong doi thap nhat dua tren su oxi boa
goc *OH. Ozon boa
6
pH cao it dugc dung va mac
toe
do phan
ling
ozon boa.
Mot dong gop hoan toan dang
chii
y den viec mo hinh boa cac AOPs khac
nhau da dugc Beltran [7,
15]
tien hanh. Hg da gioi thieu nhirng mo hinh toan hgc
thii
vi
ciia
O3 va su oxi boa
c4p
tien cac PAH, cac hgp chat nitro thom trong
nuoc va trong nuoc thai. Cac mo hinh toan hgc cua su oxi boa cap tien cac PAH
va clorophenols ciing bao
g6m
cua ca Kallas va Hautaniemi
[12].
Trong cac mo
hinh toan hgc AOPs, 3 PAH (antraxen, phenanthren va pyren)
sir
dung
O3/H2O2,
O3/UV, O3/H2O2/UV va O3 (pH 9,5) da dugc gioi thieu. Mo hinh cac phan ung
hoa hgc da dua vao xem xet
31
con duong phan
sir
ozon hoa CPs xay ra qua nhanh.
Cac phan
ling g6c
hydroxyl khong dong gop vao viec lam tang
toe
do oxi boa
CPs duoi cac dieu kien bazo.
13
^
Trong moi truong axit, co che oxi boa lai khac hoan toan. Nguoi ta da xay
dung mot mo hinh de mo phong viec
xii
ly CPs bang
O3
va O3/UV. Noi chung,
toe
do phan ung CPs khong tang len neu them
biic
xa UV so voi ozon boa mot
minh,
tiic
la
sir
oxi boa
a
cac gia tri pH thap trong ca 2 qua trinh xay ra chu yeu
qua cac phan
ling
voi phan
dung
6
dang khi da thu dugc on dinh.
Trong nha may san xuat va che bien vi mach, nuoc can rat sach. Zmolek
da xay dung mot he thong
xii
ly nuoc va lap dat o cac phong thi nghiem Bell
Telephone vao nam
1973,
voi to hgp
sii
dung
O3
de kiem soat vi khuan (vi khuan
CO
the bit cac
fil
Igc 0,2
|xm
dan den gay pha hong nghiem trgng cac nguyen to vi
r r
t
r
mach).
Tuong tu, nguoi ta cung lap dat cac he thong diet vi khuan nhu the nay
cho cong nghiep hot giay va giay. Korhonen & Tuhkanen da xac thuc nhiing tien
bg
ciia xii
ly bang O3 va
O3/H2O2
ly nay cung thanh cong va dugc lap dat cho 4
CO
so
O3/GAC
vao nam
1993.
O3,
O3/UV
va O3/H2O2 cung
CO
the giam do doc cap tinh cua dong thai tu
cong nghiep bgt giay va giay [9]. Thanh cong quan trong nhat
ciia O3
la hieu qua
o viec oxi boa pha buy cau triic cua dibenzo-p-dioxin va dibenzofuran-tien than
ciia
cac hgp chat policlorinat. Ozon boa dich trang clohoa cua bgt giay truoc lam
giam
sir
hinh thanh cac hgp chat doc nay dang ke.
Wable
da mo ta nhiing nghien cuu
xii
ly nuoc rac
6
Phap bang
O3
va
O3/H2O2.
Theo cong ty voi nhiing quy dinh moi
co bay hoi (benzen, axeton,
dicloetan,
tetrac'loetan ) tir
nuoc
ngkm
o San Jose, CA (USA)
[15].
Nhi^u
hon
90%
hieu qua cua viec loai bo la cac VOC. Trong thoi gian nam
1994,
mot he
thong UV/oxi boa dugc lap dat o nha may dan dugc
qu6c
phong Milan (Milan,
TN,
USA) de
xii
ly nuoc cac ao
tii
da nhiem ban boi cac
cbSt
no (2,4,6-
trinitrotoluen; 2,4- va
2,6-dinitrotoluen;
nitrobenzen ). Sau buoc oxi boa UV/0
, nguoi ta co the
xii
ly tiep nuoc thai bang each
voi he
O3/H2O2
neu
sir
phan quang
true
tiep khong dang ke. Khi
so sanh cac he
OVUV
va
H2O2/UV,
su sinh ra
*0H
theo phuong trinh ty lugng la
Ion
nhat tu qua trinh phan quang
H2O2,
nhung phan quang
O3
thuc te lai sinh
OH nhieu hon boi vi he so tat phan
tii ciia
O3 cao hon so voi
H2O2.
Tuy nhien, phai
chii
y so sanh nay chi la ly thuyet. Trong thuc te,
sir
san
sinh OH
tiep sau do la he O3/UV la hieu qua nhat va ky
thuat khong dat cho nha may
xii
ly nuoc uong. Mot tien bg
ciia
qua trinh
O3/H2O2
la khong doi hoi bao duong den UV (ve sinh va thay the den); hon
niia
nang lugng yeu cau luon thap hon. Cac nha may
xu*
ly da
sir
dung
O3
nhu mot
buoc
xii
ly co the
dl
dang them
H2O2
de lam tang
toe
do phan
irng.
Oxi hoa quang
xiic
tac trong
xii
hoac III),
nong do
H2O2,
pH, thoi gian phan
ling
va nhiet do phan
ling.
Gia tri pH toi uu dugc neu ra hau bet la
6
xung quanh 3 (Goi, 2002;
Neyens,
2003;
Lopez et
al,
2004). 0 gia tri pH qua cao, Fe(III) se ket
tiia
o dang
Fe(0H)3 va
H2O2
se tu phan huy thanh oxi va nuoc. Thoi gian phan
ling ciia
qua
trinh Fenton la ngan nhat so voi cac qua trinh AOP khac. De phan buy cac
phenol don gian chi can 30 - 60
phiit,
doi voi cac chat hiiu co
phiic
tap hon hay
nong do cao hon thi thoi gian phan
hiiy
chat hiiu co de hap thu lien ket voi cac halogen (AOX) hoac xac dinh do
due
de
tinh toan ham lugng clo tu do. Viec xac dinh cac thong so tren dugc tien hanh
theo tieu chuan tuong ling
ciia
Cong hoa Sec (CSN EN 1485, TNV 75 7520) va
theo Standard methods for environmental wastewater.
Cac
thii
nghiem dugc trien khai trong cac binh non dung tich 250 ml dat
tren may khuay tu.
FeS04.7H20
da boa tan dugc dua vao dung dich 4-clophenol
va tiep theo them dung dich
H2O2
30%. Hydropeoxit dugc cho vao sao cho luon
luon bao dam du gap 10
Ian
khoi lugng can thiet tinh theo ly thuyet de phan
hiiy
hoan toan 4-clophenol. Phan ling dugc tien hanh o nhiet do phong
25''C.
Trong anh huong cua thoi gian phan
ling
den hieu suat loai bo chat
biJu
CO,
n6ng
do ban
Ket qua
thii
nghiem mo ta tren hinh 1 cho thay tri so COD dat den gia tri
khong doi sau 30 phiit. Ket qua nay la hoan toan phu hgp voi cac thong so dua ra
ciia
cac tai lieu da cong bo va gop phan khang dinh ve
toe
do chung cua phan
ling Fenton (Lipczynska-Kochany et al, 1995; Hofl et al, 1997).
D6ng
thoi thoi
gian phan
ling
30 phiit nay ciing se dugc chgn
sir
dung nhu la thoi gian ket thiic
phan ling cho cac day thu nghiem tiep theo.
Hinh
4.
L
Hieu suat xir
ly COD
theo
th&i
gian phan irng
4.2.2.
Anh huong cua ty le
moi Fe"V Hn02
den kha nang loai bo AOX va
COD
OAi MUC OuOC
Gi^
^^
NO'
17
v'y/.l^i
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