Nghiên cứu xử lý các hợp chất hữu cơ khó phân hủy sinh học trong nước thải bằng các phương pháp oxy hóa cấp tiến

CBNC MUC TIEU NGHIEN CUU: - Phan loai cac chat huu co kho phan huy sinh hoc va tim hieu cac bien phap da ap dung de xii ly nuoc thai co ham lugng chat huu co cao, kho phan hiiy sinh tro

DAI HOC QUOC GIA HA NOI TRirONG DAI HOC KHOA HOC TV NHIEN

NGHIEN ClTU XLT L Y C A C HOP CHAT UlfU CO

KHO PHAN HTJY SINH HOC TRONG NlTOC THAI BANG CAC PHUONG P H A P O X Y H O A CAP TIEN

MA SO: QT-06-42

CHU TRI: ThS GVC DONG KIM LOAN cAC C A N B O T H A M GIA:

- Nguyen Thi Ha TS GV

- Luu Minh Loan ThS CBNC

- Phan Mai Linh CN CBNC

- Nguyen Quang Huy CN CBNC

- Nguyen Thi Xuan CN CBNC

- Mot so sinh vien Khoa Moi truong va can bo So KHCN&MT Ha Tay, Thai nguyen

HA NOI 2006

OAi H O C O U O C G l A HA N ^ ,

1 Ten de tai: Ma so: QT-06-42

Tieng Viet: Nghien cuu xu ly cac hop chat hiiu co kho phan huy sinh hoc trong

nirac 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

BAG CAO TOM T A T DE TAI

TEN DE TAI

Nghien cuu xir ly cac hap chat hiru ca kho phan huy trong nw&c thai bang cacphuffngphdp oxy hoa cap tien

Ma sd: QT-06-42

CHU TRI DE TAI:

Dong Kim Loan

Dan vi cong tac: Khoa Moi truong

Hoc vj: ThS GVC

Tel: 8213847/0904700062

CAC CAN B O THAM GIA DE TAI

- Nguyen Thj Ha

- Luu Minh Loan

- Nguyen Thj Mai Linh

- Nguyen Quang Huy

-Nguyen thi Xuan

TS GV ThS CBNC

MUC TIEU NGHIEN CUU:

- Phan loai cac chat huu co kho phan huy sinh hoc va tim hieu cac bien phap da

ap dung de xii ly nuoc thai co ham lugng chat huu co cao, kho phan hiiy sinh trong nuoc va tren the gioi

- Ap dung thir mot so phuong phap oxy hoa cap tien de xu ly chat huu co kho phan huy sinh hoc

- Che tao xiic tac quang hoa Ti02 cho xu ly nuoc thai chua nhieu chat hiru co kho xir ly sinh hoc

N O I D U N G 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

cuu cua 6k tai la thiet bi xu ly tuan hoan nuoc thai c6 den tu ngoai va mot

thiet bi xu ly mang Ti02 /UV

- Mot bo phan ung de nghien cuu phan ung Fenton

- Da che tao dugc mot so vat lieu mang Ti02 va mang Ti02 cho xu ly chat thai

- Da xay dung dugc quy trinh cong nghe phu hgp cho viec xir ly nuoc thai det nhugm

- Da cong bo 02 bai bao trong Proceedings ve "New trends in technology towards sustainable development", RSCE 12/2005 va Tap chi Khoa hgc-Khoa hoc tu nhien va cong nghe, T 22 (3B), 2006

- Hai khoa luan cu nhan nganh Cong nghe moi truong

TINH HINH KINH 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

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"

Hgp dong NCKH "Che tao mang Ti02 cho xu ly

moi truong"

Hgp dong NCKH ve "Nghien cuu su dung xuc tac

Ti02 the lo lung va mang Ti02 de xu ly nuoc thai

det nhugm"

Photocopy, in an tai lieu

Thanh toan tien dien, nuoc va co so vat chat

>

Thanh tien

4.250.800 2.600.000

2.600.000

3.000.000

169.200 600.000

Muc

•

119/01 114/06

114/06

114/06

119/03 109/01

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

110/01 112/02 112/99 119/99

XAC NHAN CUA BAN CHU NHIEM KHOA

XAC N H A N CUA TRUCING

CHU TRI DE TAI

^^T "^ '^^^^

HO HIEU T t U O N G

^^s.isM^SLM '^<ya/nt

THE SUMMARY OF THE REPORT

Project Title:

Investigation for treatment of biorefractory organic compounds in wastewater by advanced oxidation processes

Main Responsible Person/Author:

Master Science Dong Kim Loan, Senior Lecturer

Combained Responsible Persons/Coordinaters:

- Dr Nguyen Thi Ha

- MSc Luu Minh Loan

- BS Phan Mai Linh

- BS Nguyen Quang Huy

- BS Nguyen Thj Xuan

- Some Students and Experts in Environmental Technology

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

-Some granulated and thin films ofTi02 were Prepared for treatment waste

-A suitable technical model was supposed for treatment dye wastewater

BAO CAO CHI TIET KET QUA DE TAI

MUC LUC

Loi noi dau 1

1 Modhu 2

2 Cac chat huu cokho phan huy sinh hoc va cong nghe xu ly 2

3 Qua trinh oxy hoa cap tien va kha nang ung dung 5

4 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 Xu ly nuoc thai det nhuom bang he xiic tac hat Ti02/UV 25

6.2 Xu ly nuoc thai det nhuom tren he xiic tac mang Ti02/UV 30

6.3 So sanh hieu qua xu ly tren hai he Ti02 va de xuat day chuyen

cong nghe xu ly nuoc thai det nhuom 32

7 Ket luan va kien nghj 34

Tai lieu tham khao 35

L6I NOI DAU

Bao ve, duy tri va gin giii nguon tai nguyen nuoc la nhiem vu cua tat ca cac quoc gia tren toan the gioi Trong do viec tim kiem cac giai phap hiiu 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

L M&dau

Mot trong nhiJng dang 6 nhiem nuoc pho bien la 6 nhiem nuoc do cac hgp chat hGu co gay ra Nguon gay 6 nhiem nay kha da dang, trong do chu yeu la chat thai tir cac khu dan cu, cong nghiep, san xuat hoa chat va nong nghiep Dua vao kha nang phan huy sinh hgc co the chia cac chat huu co gay 6 nhiem thanh hai loai:

-Cac chat huu co de phan huy sinh hgc: cac chat nay phan Ion la cac protem, hydratcacbon, chat beo co nguon goc dong vat va thuc vat Day la cac chat 6 nhiem chinh co nhieu trong nuoc thai sinh boat, nuoc thai tir cac nha may che bien thuc pham Cac hgp chat nay chu yeu lam suy giam oxy hoa tan trong nuoc, de gay mui hoi thoi kho chiu do phan huy nhanh trong nuoc

-Cac chat huu co kho phan hiiy sinh hoc hay chat huu co doc hai la nhung chat CO kha nang uc che cac qua trinh xu ly sinh hoc, gay hieu ung bat 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 cung nhu gia ca de xu ly Oxy hoa cap tien la mot huong nghien cuu dugc nhieu nha khoa hgc tren the gioi quan tam nhat trong nhiing nam gan day Nho nhiing tinh chat uu viet cua no va kha nang tao cac vat lieu voi nhGng hieu ung nano hap dan no da tro thanh nganh "hoa hoc cua the ky 2 1 " [15]

2 Cac hap chat hiru ca kho phan huy sinh hgc va phirangphdp xir ly

2.1 Phan loai

Mot so nhom chat huu co kho phan huy sinh hoc pho bien la:

2.1.1 Cac hop chat co clo (chu yeu la cac clorophenol)

Cac hgp chat clorophenol la cac dan xuat clo cua phenol bao gom clorophenol; 2,4-/2,3-/3,4- diclorophenol; 2,4,6-/2,3,5-.,.triclorophenol cho

2-/3-/4-den pentaclorophenol Cac hgp chat nay dugc tao ra trong cong nghiep san xuat chat bao quan, san xuat bgt giay, go, thuoc bao ve thuc vat, san pham cua qua trinh tay trang bang hgp chat clo, san pham cua qua trinh thieu dot chat thai nguy hai 4-clorophenol con la chat trung gian trong qua trinh phan 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 2,4-chlorophenol trong nuoc mat khong dugc vugt qua 2,02 mg/1

2.1.2 Thuoc nhuom

Nhom cac chat hiiu co su dung trong qua trinh nhuom mau (chu yeu trong det nhuom va giay in mau) phan nhieu cung la nhiing chat kho phan hiiy sinh hgc Cac thuoc nhuom thuong rat ben vu"ng trong moi truong, c6 mau dam dac

va kho phan huy do da phan co cau triic thom, ngung tu chua cac di nguyen to Trong so do cac hgp chat mau azo dugc quan tam nhieu hon ca do khoi lugng sii dung Ion, ben Mot so thuoc nhuom con gay lic che boat dong cua cac vi sinh vat phan hiiy chat h&u co Mat khac do cac chat huu co trong thuoc nhuom kh6ng"tan trich" 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 thay sau tram xu ly nuoc cap 2 va cap 3 van phat hien tha}' chiing o co vai tram

ng/1 den \x%IV Vi the chiing thuong dugc loai truoc khi ap dung mot bien phap

sinh hgc nao do de xu ly nuoc thai

2.1.4 Cac thuoc bao ve thuc vat

Cung tuong tu, chiing la nhirng hgp chat hiiu co thom hoac beo voi so nguyen tu cac bon Ion trong phan tii Nhom cac chat nay thuong tren co so hgp chat huu CO di vong chiia kim loai, halogen, nito, phospho, luu huynh Da phan cac thuoc bao ve thuc vat la nhiing chat doc cham va kho phan hiiy sinh hoc

Ngoai ra, cac chat hiJu co hay dugc xu ly bang AOPs con la cac 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

Hien co kha nhieu cac phuong phap xu ly cac chat kho phan hiiy sinh hoc nhu thieu dot, chiet long-long, hap phu, keo tu, tham thau ngugc, oxy hoa h6a hoc, xii ly hoa hgc ket hgp voi sinh hoc va oxy hoa cap tien Tuy nhien, viec lira chon phuong phap xii" ly cho phu hgp can can cii vao luu lugng, nong do chat 6 nhiem, chi phi cho qua trinh xu ly, yeu cau va miic do phai xu ly O day tap trung vao mot so cac qua trinh oxy hoa cap tien vi nhiJng ly do sau:

-Doi tugng nghien cuu la cac chat hiiu co doc, ben va kho phan hiiy sinh hoc

-Cac qua trinh oxy hoa cap tien (AOPs) la qua trinh oxy hoa chat hiiu co bang nhiing tac nhan co the oxy hoa cue Ion 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 de loai bo cac chat doc hoac cac chat ben

vi sinh truoc khi xu ly sinh hoc

3 Qua trinh oxi hoa cap tien va kha nang ung dung

De khac phuc nhimg nhugc diem la xir ly rat dat hoac khong triet de ciia cac phuong phap khac va de giam gia thanh cung nhu tang hieu qua xu ly cac chat hiiu co doc, ben sinh hoc; nhom cac qua trinh oxy hoa cap tien (advanced oxidation processes) da ra doi dua tren kha nang tao ra the oxy hoa rat cao cua tac nhan oxy hoa hoa hoc da su dung AOPs rat hieu qua trong viec loai bo hang loat cac chat 6 nhiem hiiu co kho phan hiiy nhu cac fenol, foocmandehit, cac chat hiiu co de hap thu lien ket voi cac halogen (AOXs), cac chat mau va nhom cac thuoc tru dich 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 Tuy nhien do phai thuc hien o dieu kien nhiet do va ap suat cao nen gia thanh xu ly dat cung nhu thiet bi thuong kho kiem va nguy hiem

3.2 Tao goc hydroxyl

Day la nhom cac phuong phap tren co so cac chat oxy hoa hoa hgc thong thuong nhung bo sung them tac nhan lam tang kha nang oxy hoa trong cac phan ling trung gian de phan hiiy chat hiiu co den CO2 va H2O Cac qua trinh nay xay

ra do sir xuat hien cua cac goc hydroxyl tu do co the dien hoa rat cao Chinh qua trinh sinh goc tu do da tao dieu kien phoi hgp cac chat oxi hoa thong thuong nhu H2O2, O3 voi O2 hay ion kim loai hoac voi tia cue tim (UV) de tro thanh he thong xiic tac 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 [15]

Bang J 7 Nang luc oxy hoa

Chat oxi hoa

Chal oxi hoa

HCIO

0 (ng.tir)

The oxi hoa

1,10 1,78

Chaloxi hoa

KMn04 'OH

Thcoxi hoa

1,24 2,05

Chat oxi hoa

H7O,

The oxi hoa

1,31 Ti02'(h*) 1 2,35

Goc hydroxyl la mot tac nhan oxy hoa manh, khong chon loc voi hau het

cac chat huu co Hieu qua xu ly chat huu co phu thuoc rat nhieu vao nong do goc

OH sinh ra De tao cac goc hydroxyl, hai nhom cac ky thuat oxy hoa cap tien dugc dua vao la:

3.2.1 Ky thuat oxy hoa cap tien khong quang hoa (non-photochemical)

Co 4 phuong phap hay dung de tao ra goc OH ma khong can anh sang quang hoa, bao gom:

* Ozon hoa 6* pH nang cao

Khi tang pH, toe do phan buy O3 trong nuoc tang Vi du 6 pH = 10, thoi gian ban phan huy ciia 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 + OH" + H" > 2*0H + 4O2 (3.1)

Ion cacbonat va bicacbonat dong vai tro quan trong nhu loai tieu thu goc

OH trong cac he thong tu nhien Cac san pham phan ung giua chiing la cac goc cacbonat va bicacbonat mang dien tich duong nen khong tuong tac tiep voi ozon

va chat huu co Vi the su c6 mat cua mot so anion nhu HCO3", CO^^', S04^' va

Cr trong nuoc va nuoc thai khong co Igi cho su tao thanh OH Tuy nhien viec sir dung ozon thuong dat do gia thanh dien phan sinh ozon

* Ozon hoa ket hap vai H2O2 (O3/H2O2 - phan i>ng peroxon)

Viec them H2O2 vao O3 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 phan hiiy thuoc tru sau tot hon phan buy bang mot minh O3 Ty le khoi lugng H2O2/O3 toi uu la 0,35-0,45 Hieu suat qua trinh phu thuoc vao lieu ozon, thoi gian tiep xuc, do kiem cua nuoc

Theo Duguet et al [7] thoi diem bat dau dua H2O2 vao be xu ly rat quan trong Hieu suat tot nhat dat dugc khi H2O2 dugc them vao sau khi da oxy hoa cac chat co kha nang phan ung cao voi mot minh O3 R6 rang viec bo sung cac goc CO kha nang oxy hoa cac phan tu kho phan hiiy da tao ra Igi the cho phan tu O3 phan ung chon Igc truoc khi c6 su tan cong cua goc tu do khong chon Igc Hydropeoxit la mot chat oxy hoa khong dat va de kiem

* Ozon hoa co xuc tac (O3/CAT)

Co hoi khac de thuc day cac phan ung ozon hoa la 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 hon he O3 hoa 6 pH cao Cac he 03/Mn(n) va 03/Fe(lI)

hieu qua hon trong viec loai cac hgp chat co clo so voi he 03/Fe(III) va O3 o pH

Kaptijn [13] cho thay, oxy hoa cac chat \iu\x co kho phan 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+

Fe'" + Fe'" + Fe'" +

H2O2 -> Fe^" + HO2' +

HO2* -^ Fe-" + O2 + H"

R' -> Fe'" + R"

Co so cua phan ung Fenton la phan ung cua ion Fe*" va hydropeoxit trong

moi truong axit [18], Phan ung xay ra theo phuong trinh sau:

Fe^^ + 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: O H ' + CH3OH-^ CH20H'+ H.O (3.10)

- Trao d6i electron: OH' + [Fe(CN)6]''" -^ [Fe(CN)6f" + OH' (3.11)

- Tuong tac goc - goc hydroxyl phan ung voi cac goc tu do khac tao thanh

cac san pham bSn hon: OH' + OH' ^ H2O2 (3.12)

Trong xu ly nuoc thai bang phan ung Fenton, nguoi ta phai co gang tao

dieu kien ban dau sao cho xay ra hai qua trinh theo co che ciia phan ung (3.9) va

(3.10) ( CO che phan ung cong va dehidro hoa)

3.2.2 Ky thuat oxy hoa cap tien quang hoa

Cac phan ung oxy hoa pha hiiy 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"')

tao ra H2O2 nhu mot chat trung gian sau do phan tach thanh OH [9]

O3 + hu > O2 + 0 ( ' D ) ( 3 1 3 )

0 ( ' D ) + H2O > H2O2 > 2*0H (3.14) San xuat *0H theo each nay thuong la dat do den Hg ap suat thap thong

thuong phat sinh > 80% nang lugng UV cua chiing o buoc song nay Tuy nhien

do do hap thu phan tii' gam thap cua H2O2 6 254 nm (£254 nm = 18,6 M"'.cm"'),

nen da gioi ban san lugng goc *0H trong dung dich (neu dung H2O2 de tao OH)

Phan quang chi dung O3 sinh cac goc tu do nhieu hon dung 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:

- — > 2 OH -_„> 2 'OH

' O H /photon 0,09

2,00

Neu dung dich nuoc chua cac hgp chat hiiu co hap thu manh anh sang

UV, thi them buc xa UV khong lam tang len hieu qua xu ly bang O3 boi vi cac

hgp chat quang boat nhu phenol, 5-methylresorcinol, xylenols da hap thu het

tia UV den ozon Mac du cac hgp chat phenolic (phenol, p-cresol, 2,3-xylenol,

3,4-xylenol) bi ozon oxi hoa de dang, nhung su khoang boa cung hiem khi hoan

toan den CO2 va H2O Su dung he O3/UV, viec khoang hoa hoan toan hieu qua

voi cac hgp chat hiiu co c6 mach cacbon ngan (glyoxal, glyoxylic axit, oxalic

axit, foocmic axit)

Qua trinh H2O2/UV dugc su dung thanh cong de phan hiiy cac

clorophenol va cac hgp chat clo hoa khac nhau Cac phan tii" nhu atrazine,

desethylatrazine va simazine co the bi khoang hoa den tan CO2 trong thoi gian

buc xa CO mat H2O2

**03/H202/UV

Them H2O2 vao qua trinh O3/UV da thiic day su phan buy O3 lam tang

toe do sinh *0H Dac biet trong cac qua trinh ma chat 6 nhiem hap thu yeu tia

UV, thi chi can mot nguon UV nho them H2O2 se co hieu qua hon

Bang 3.4 So sdnli gia lioat dong ciia mot vai qua trinh AOP

Qua trinh

O3/UV

O3/ 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

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 cac AOPs khac nhau

* Quang hoa-Fenton va cac he kieu Fenton

Khi ion Fe^^ dugc them vao he H2O2/UV, qua trinh dugc ggi la oxi hoa quang boa kieu Fenton 6 pH 3, phuc Fe(OH) dugc hinh thanh vi moi truong axit theo phuong trinh:

Fe^" + H2O > Fe(OH)'' + H"

Fe(OH)^^ ^ Fe^^ + OH'

Cho tiep xuc voi tia UV, phuc bi phan hiiy tiep sinh OH va ion Fe

Fe(OH)^^ + hu > Fe^^ + *0H (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 buoc song 250 nm Mat khac, pho hap thu cua ion Fe^^ (va hoac ion hydroxy sat 3) keo dai den vung

UV gan VIS hoac VIS va co mot he so tat rgng hon, vi vay co the oxi hoa-quang hoa va khoang hoa tham chi bang anh sang trong vung nhin

Viec hinh thanh Fe(II) khong phu thuoc vao buoc song buc xa trong khoang 250-450 nm (UV/VIS) va giam dan neu buc xa co buoc song dai hon

* 0x1 hoa quang xuc tac (UV/Ti02)

Co so cua quang xiic tac la sir kich thich quang cua mot chat ban dan ran (SC) sau khi hap thu buc xa dien tu Duoi cac tia buc xa gan UV, mot vat lieu ban dan b^n co the bi nhung photon co nang lugng dii Ion kich thich phat ra electron (e) va nho the hinh thanh nen cac khoang trong electron (ggi la 'Mo trong boa tri h""") co tich dien duong ao Nhu'ng phan tu mang dien tich nay (e, h^) 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" + O2 ^ *02 ; h^ + OH" -^ *0H ; h* + RH ^ ' R H * -^ cac san pham

10

w

Cac 16 trong h"^ co the oxi hoa cue ky duong va boi the co the oxi hoa hau het cac chat boa hgc, tham chi oxi boa mot electron ciia nuoc de hinh thanh cac goc hydroxyl nen rat kha thi ve mat nang lugng

H2O + h^ -> *0H + H^

Mot chat xuc tac quang hgc tot phai bao gom hai tinh chat: (i) hap thu tot proton, (ii) hap phu tot cac chat phan ung

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 6 buoc song khoang 300 nm

Thuc te, tat ca cac loai hgp chat doc hai deu co the bi phan hiiy bang tac nhan oxi boa quang xiic tac (PCO) Cac hydrocacbon halogenua bi khoang boa hoan toan Cac phan tii thom ciing bi oxi boa mot each dinh lugng Cac phenol, biphenol da clohoa va tham chi dioxin cung bi oxi boa hoan toan sinh CO2 va HCl Mot bang chung la cac san pham phu doc hai khong hinh thanh tham chi chi mot lugng vet Cac thuoc nhugm, cac phthalate, DDT va chat boat dong be mat cung dugc khoang boa tot boi xiic tac nay [4 ]

Chinh vi the, hau het cac boat dong nghien cii'u ve ITnh vuc xii ly chat thai chiia 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 nhiem Boi the, da co mot vai de xuat va mo hinh dugc gioi thieu [7, 8, 13] Glaze [9] da dua mot mo hinh oxi boa dung djch nitrobenzene dam dac sii dung cac ky thuat AOP khac nhau nhu: O3 6 pH cao, O3/H2O2, H2O2 /UV va O3AJV

Uu diem va nhugc diem ciia moi qua trinh dugc xac dinh Nghien ciiu nay cung cho thay mot vai gioi ban ung dung AOPs dien hinh cho xu ly nuoc thai dam dac Trai ngugc voi sir oxi boa mot vai chat 6 nhiem vi lugng trong nuoc tu

11

nhien (nuoc ngam, nuoc qua 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 H2O2 co t6c do oxi boa cao hon va thoi gian song ngan hon cua cac chat huu co so voi chi phan quang Qua trinh oxi hoa H2O2/UV dugc cho rSng do sir hoat dong ciia cac loai goc khac nhau (khong chi bao gom goc hydroxyl, ma co le ca g6c ion cacbonat)

Hirvonen [10] da nghien ciiu tinh kha thi cua viec xii ly lam sach nuoc ngSm nhiem bSn TCE va PCE (TeCE) bang O3/H2O2 va H2O2 /UV Ca hai 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 [19] Nghien ciiu nay cho ket luan hieu suat ciia AOPs doi voi sir oxi boa antraxen theo thu tu sau:

O3/H2O2 - O3 > O3/UV > O3/H2O2/UV > UV

Ket qua tuong tu cho cac PAH khac R6 rang o day cac goc OH dong vai tro thii yeu trong viec phan buy antraxen

Oxi hoa cac nitrophenols voi O3 va O3 ket hgp voi H2O2 va hoac tia UV cung da dugc Trapido nghien ciiu [18, 19] Tat ca nhung qua trinh nay deu co 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 cii'u khac nhau

de dua ra mot so lugng Ion cac chat oxi boa doi hoi ve mat ly thuyet nham thu dugc mot so lugng cu the cac goc OH (bang 5)

12

"^^

Bang 5 Luang chat oxi hoa ve mat ly thuyet va UV doi hoi cho su- hinh thanh goc

OH trong cac he 63/H2O2/I/V

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 dii he O3/UV duong nhu kho thuc hien tren mot pham vi Ion, nhung no co the dugc diing thanh cong 6 toe do dong chay nho hon

Trong 10 nam lai day, mot vai mo hinh AOPs da cho phep nghien ciiu tot hon ve co che qua trinh Glaze va Kang [9] da mo ta mot mo hinh dong hgc cua qua trinh O3/H2O2 dua tren thuc nghiem voi PCE nhu mot hgp chat mau Mo hinh dua vao tinh toan lieu lugng O3 va H2O2, sir chuyen khoi O3 va cac phan ling tieu thu g6c Peyton [7] da gioi thieu mot mo hinh dong hgc cua qua trinh O3/UV Mo hinh nay quan tam toi thong lugng biic xa, nong do O3 trong pha long va he so 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 ling co the xay ra So lugng lugng tii cung nhu bSng s6 t6c do phan ling ciia phan tii O3 va goc OH cho PAHs dugc danh gia tu cac dii lieu thuc nghiem Ket qua cho thay hang so toe

do phan ling trong xii ly PAHs bang cac qua trinh AOP co cac gia trj tuong doi thSpgiualO^^- 10^M"'s"'

Trong cac cong trinh [8, 11] cac mo hinh toan hgc oxi boa cap tien 3 clorophenol (2-CP, 4-CP va 2,4-CP) trong cac dieu kien axit va bazo cung dugc xay dung Duoi cac di§u kien bazo (pH 9,5) 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 tii ozon

Tom iai, ozon boa va nhiing to hgp cua no voi H2O2 va/hoac tia UV la cac

phuang phap xii ly tuyet voi cho cac chSt thai doc hai khac nhau Cac he thong

O3/UV da dugc lap dat 6 Can cii Khong quan Tinker (Oklahoma, USA) [17] de

xu ly phuc xianua kim loai va chat hiiu co kho phan hiiy Nam 1978 xu ly bang O3 da dugc lap dat o Phong (Division) thiet bi dong co 6 to cua Tong cong ty O

to Cadillac tai Detroit, Michigan (USA) Tii do miic CN" tong trong dong chay

da ha xuong < 1 mg/1 va > 99% O3 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

Ozon cung voi GAC [8, 16, 17] la mot sir lira chon tot cho giai phap ve cac van de moi truong ciia cong nghiep dau mo Cong ty ARCO Products (nay

da dong cii'a) xu ly mot trieu gallon nuoc thai dau mo hang nam 6 Richmond,

CA (USA), kho chiia san pham dau va nhiing phuong tien van chuyen de dang dau mo tu nam 1991 He thong xii' 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 ciia Phap, nuoc rac phai dugc xu

ly truoc khi thai ra moi truong Leitzke da thao luan ling dung oxi boa boa hgc bang to hgp O3/UV cho nuoc rac cua Due truoc khi xu ly sinh hoc Oxi hoa boa hoc dugc sir dung de lam giam mii'c cac chat 6 nhiem bay hoi nhu cac

14

w

hydrocacbon, cac hydrocacbon da clohoa, cac hgp chat sulfua 6 15-20 cac nha

may xii ly dia phuong 6 Diic va Ao

Ky thuat oxi boa kem theo chieu biic xa cue tim ( O3/H2O2/UV) dugc ung

dung thanh cong cho viec loai cac chat ban hiju 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 Igc qua than boat tinh (GAC)

Nam 1994, mot he thong xii ly UV/O3/H2O2 da dugc lap dat o co quan (point)

Bofors Nobel Superfund, dong gan Muskegon, MI (USA) de phan buy nuoc thai

doc hai chiia benzen, toluen, clobenzen, tetracloetan, benzidin

Nhu vay, neu dugc sii dung mot each diing dan, cac AOPs noi chung, se

cho kha nang oxi boa cao hon mot minh ozon Tuy nhien chiing can dugc danh

gia hieu qua, gia ca va miic do oxi boa Nen chii y rang AOPs khong phai la rat

hieu qua de xii ly dong thai that dam dac voi nong do chat 6 nhiem hiiu co vai

tram den 1000 mg/1 Tu quan diem hoa hgc ciia tong quan, hieu qua cua O3/UV

> t t t

la ngang bang 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 Ion co the dan dtw toe do phan ling thap hon vi cac goc tai to hgp lai

% t i l

deu dan va khong tien ich cho qua trinh oxi boa Boi the de co mot hieu suat

AOPs mong uoc cho mot hgp chat cu the, viec lira ebon he thong AOP cuoi ciing

can dugc lam sau khi c6 khao sat so bg trong phong thi nghiem Viec so sanh

chung hieu qua xu ly ciia cac hgp chat hiJu co hoac v6 co khac nhau trong nuoc

la khong can thiet

De loai miii, vi va khu triing nuoc uong chi mot minh O3 la dii Trong

truong hgp co mot vai chat 6 nhiem vi lugng trong nuoc (TTS, huu co

clorinat ) thi to hgp O3/H2O2, 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 ly nuoc da chiing to hieu qua ciia no trong

nhieu ling dung thuc te

15

4 Nghien citu loai bo cac hap ch&t ca clo bdng tac nhan phan irng Fenton

4.1 Xay dung thiet hi vd cac dieu kien nghien cuu

Do dugc su dung rat rgng rai va co hieu qua, nen cac qua trinh Fenton lien tuc dugc nghien ciiu, cai tien va hoan thien them Cac tai lieu tham khao cong bo cho den nay da dua ra cac ket qua nghien ciiu lien quan den anh huong ciia mot loat cac nhan to nhu nong do va miic do oxi boa cua cac ion sat (II 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 ciing chi tinh bang gio (Hofl et al., 1997; Martinez et al., 2003; Neyens, 2003) Theo mot so nguon thong tin khac cho

r r r

thay tang nhiet do phan ling se c6 anh huong tot den dong hgc ciia phan ling va

khoi lugng chat dugc phan hiiy (Lopez et al., 2004)

Boi vi phan ung Fenton dugc coi la giai phap huu hieu cho qua trinh phan hiiy cac hgp chat hiiu co chiia halogen trong nuoc thai, cho nen trong nghien ciiu nay chiing toi da chgn 4-clophenol (4-CP) la chat dai dien cho cac thu nghiem cua minh

Qua trinh phan buy dugc theo doi thong qua chi thi la COD va nong do 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 d4u ciia 4-CP la 320 mg/L va ciia Fe"" la 20 mg/L Dung dich trong binh non dugc khuay manh va cii sau thoi gian la 0, 15, 30, 60 va 120 phiit mau dugc lay ra de phan tich COD

Trong anh huong ciia ty le chat xiic tac Fe"^ va H2O2 den hieu suat loai bo AOX va COD, mot day thi nghiem dugc tien hanh voi cac nong do Fe~* khac nhau Cac dieu kien thi nghiem khac giong nhu truong hgp dau Bao gio cung

sau 30 phiit khuay manh thi \iy mau va xac dinh nong do AOX va gia tri COD

trong do

4.2 Ket qua nghien cuu vd thao luan

4.2.1 Anh huong cua thoi gian phan ling

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

Ket qua tren hinh 2 chiing to hieu qua ciia qua trinh phan buy phu thuoc kha ro vao ty le nong do cua cac thanh phan xiic tac sat(II) va nguon san sinh ra cac goc hydroxyl - H2O2

Trong qua trinh thii nghiem, ty le moi ciia Fe"7H202 dugc thay doi tu 1:

120 den 1:1640 Ket qua nghien cuu thay rang khi nong do sat(II) giam thi hieu qua xii ly AOX cung nhu COD deu tang va hieu qua cao nhat khi sir dung ty le 1:810, 1:980 va 1:1230 Khi nong do sat(II) tiep tuc giam thi hieu qua xir ly ciing giam

O A i MUC O u O C G i ^ ^^ N O '

Hinh 4.2 Anh hw&ng cua ty le moi Fe^^/H202 den hieu suat xu ly AOX va COD

Hien tugng tren co the dugc giai thich bang cac co che sau:

* Khi nong do sat(II) qua cao se dan den su giam so lugng cac goc hydroxyl do xay ra cac phan ung phu (Neyens, 2003):

O H ' + Fe^^-^ OH" 4-Fe'^ " (4.1)

* Ngugc lai, khi nong do sat(II) qua thap se dan den viec giam toe do ciia phan ling

Trong tat ca cac thii nghiem da tien hanh deu cho thay hieu qua giam AOX luon luon cao hon hieu qua giam COD; dieu nay cung phii hgp voi so lieu

ciia cac cong trinh nghien ciiu da cong bo tuong tu (Hofl et al, 1997)

Tom lai, Phan ling phan buy 4-CP bang tac nhan Fenton xay ra nhanh (c6 thoi gian phan ung ngan), COD dat gia tri khong doi trong khoang 30 phiit

Trong moi truong hgp cu the khi ap dung phan ling Fenton can thiet phai

9-*-tim ra nong do toi uu ciia cac tac nhan Ty le moi Fe / H2O2 luon dong mot vai tro quan trgng; khi ty le nay qua cao hay ngugc lai qua thap deu dan den sir giam hieu qua xii ly cua qua trinh

Trong tat ca cac thii nghiem da tien hanh, hieu qua xii ly AOX (> 97%) luon Ion hon hieu qua xii ly COD (>65%), chiing to hau bet cac hgp chat co clo

da bi pha buy, nhung co the chua bi pha buy hoan toan den CO2 va H2O

5 Nghien ciiu che tao xiic tac Ti02

Co nhieu phuong thiic sii dung Ti02 lam xiic tac trong xii ly nuoc thai, tap trung vao 2 nhom chinh:

-Sii dung Ti02 dang bgt (buyen phii phan tan trong nuoc thai)

-Phii Ti02 len be mat ciia vat lieu ran khac (co dinh)

18

Cach thii 2 co uu dilm la khong cSn tach va thu hoi lai Ti02, nhung nhugc diem la dien tich tiep xiic nho hon va ky thuat gan chat xiic tac len nen chat mang Hien quan tam nhieu hon den co dinh Ti02 len vat lieu mang do mot mat khac phuc nhugc diem ciia phuong phap 1, mat khac c6 the tim each tao be mat neng phat trien tren nen cac vat lieu khac voi cac phuong thiic cu the nhu: dua len chat mang ran tro nhu kim loai, plastic, thiiy tinh, cat bang each phii, ket tua, xoay tron, dien phan sau do ap dung vao xu ly [21, 22] Trong khuon kho ciia de tai chiing toi tap trung vao viec che tao xiic tac theo phuong phap phii hoac son nhiing va tao vat lieu dang hat Ti02 bang each tao cac tien to Ti02 trong chinh mot vat lieu hat xop nao do

5.1 Che tao vat lieu hat mang Ti02

De khac phuc nhugc diem ciia phuong thiic dua buyen phii Ti02 vao chinh dung djch can xu ly, nguoi ta thuong tim each dua cac tieu phan Ti02 len nhiing chat mang xop bang each dong ket tiia [21 ] de thu dugc vat lieu xiic tac c6 kich thuoc thich hgp, de sii dung (khong bi troi theo dong thai) va de thu hoi

5.1.1 Che tao vat lieu hat TiO^/Silicagel

Dong ket tiia hydroxit dang keo cua Ti(0H)4 va Si(OH)4 tii* cac dung dich

muoi TiCU va thiiy tinh long Lgc, riia ket tiia cho den bet ion CI' Say kho trong

khoang 2h 6 nhiet do 150"C San pham thu dugc dem nghien nho lay kich thuoc 0,1-1,0 mm

"2000nm

Hinh 5 / Cau true be mat hat TiOi/SiOi chup tren kinh hien vi dien tir quet

Tu ket qua tren anh chup kinh hien vi dien tu quet (SEM) va xem xet bang mat thuong chiing toi nhan thay gel Si02 mang theo cac tieu phan Ti02 co dang nhay, kho rira Co le each tao vat lieu nay chua on

19