mSc d4u H. J . H. Fenton da p h a t hien ra ion s4t(II) co kha nang xuc tac cho phan ttng oxi h6a axit malic b a n g H2O2 tii nam 1894.
Nhvf t r i n h bay d p h i n tren, cd sci cua p h a n iing Fenton la phan iing cua ion Fe^*
vk hydropeoxit trong moi trUdng axit. P h a n iing xay ra theo phiidng trinh sau:
Fe^* + H2O2 -^ Fe^* + OH + OH" (1) Ion Fe^* h i n h thiinh c6 the tiep tuc p h a n iing v6i H2O2 de tao goc hydropeoxyl va
chinh qua t r i n h nay lai tai tao ion Fe^*. Qua trinh hinh t h a n h va tai tao nay ciing c6 t h i phan iing v6i cac goc hiiu cd (nhii cac p h a n iing 2, 3 va 4)
Fe^* + H2O2 -^ Fe^* + HO2' + H^ (2) Fe^* + H02" ^ F e ^ ^ + O2 + H^ (3)
Fe^* + R- -> Fe^* + R^ (4) Cac goc hydroxyl hinh t h a n h (theo p h a n iing 1) se oxi hoa cac chUft 6 n h i l m . Cac
qua trinh oxi hoa nay co the x^y ra theo cac cd che sau:
* Cd che phaA iing cong - goc hydroxyl p h a n iing v6i cac hdp chllft khong no, cac hdp ch4't b6o h a y cac hdp chS't thdm de hinh t h a n h cac goc tu do tiidng iing:
OH- + CgHe - • (OH)C6H6' (5) * Cd che p h a n iing dehydro hoa:
OH' + CH3OH -> CH2OH' + H2O (6) * Cd che p h a n iing t r a o doi electron:
OH- + [Fe(CN)6]'' -> [Fe(CN)e]'- + OH" (7) * Cd che p h a n iing tifdng tac goc - goc hydroxyl phan iing v6i cac goc tii do khac
tao t h a n h cac s a n p h a m ben hdn:
OH- + OH* ^ H2O2 (8)
Trong xxi ly nii6c t h a i bang p h a n iing Fenton, ngvfdi ta phai co ging tao dieu
kien ban dau sao cho xay r a hai qua t r i n h theo cd che cua p h a n iing (5) va (6) ( co che phan iing cong va dehidro hoa).
Do diidc s i d u n g r a t rong rai va co hieu qua, cho nen cac qua trinh Fenton lien tuc diidc nghien ciiu, cai tien va hoan thien them. Cac tai lieu t h a m khao cong bo cho den nay da diia ra cac ket qua nghien ciiu h e n q u a n den anh hiidng cua mot loat cac
nhan to nhii nong do va miic do oxi hoa cua cac ion s^t ijl hoac III), nong do H2O2, pH,
thdi gian p h a n iing va nhiet do p h a n iing.
Gia tri pH toi liu diidc neu r a h ^ u h e t la d xung quanh 3 (Goi, 2002; Neyens, 2003; Lopez et al., 2004). 6 gia tri pH qua cao, Fe(IID se ket tua c( dang Fe(0H)3 va H2O2 se tii p h a n h u y t h a n h oxi va niidc. Thdi gian p h a n iing n^m trong nhom AOP co thdi gian p h a n iing ng4n nh^'t. De p h a n h u y cac phenol ddn gian chi c^n 30 - 60 phut,
Phan huy c ^ chit hihi eg d6c hai...
doi v6i cac chi't hiiu cd phiic tap hdn hay nong do cao hdn thi thdi gian phan buy cung chi tinh b i n g gid (Hofl et al., 1997; Martinez et al., 2003; Neyens, 2003). Theo mot so nguon thong tin khac cho th^'y t a n g nhiet do p h a n iing se co anh hiidng tot den dong hoc cua phan iing va khoi lUdng ch^'t dUdc p h a n buy (Lopez et al., 2004).