Environmental Engineering Reference
In-Depth Information
C
M: muscovite; C: calcite, Q: quartz; Pt: portlandite; H:
hatrurite; CM: calcium magnesium aluminum oxide
silicate; Ca-As-O: calcuium arsenite
Ca-As-O
CM
H
Pt
CM
H
CM
Q
H
CM
C,Q
C
C C
M,C
Pt
H C
Q C,Q
As 3+ -CKD
Pt
C
C
M
Ca-As-O
CM,H
CM,H CM,H,Pt
CM,H CM,H
C
H
Pt
As 3+ -PC
5
10
15
20
25
30
35
40
45
50
55
60
65
(a)
2 θ
M: muscovite; C: calcite, Q: quartz; H:Hatrurite; CM:
calcium magnesium aluminum oxide silicate; NCA:
sodium calcium arsenate (NaCaAsO4.7.5H2O); CaSi:
calcium silicate
CM
H
NCA
CaSi
NCA
C
NCA
CM
M
NCA
H
CaSi
CM,H,Casi
C
C C
CM
NCA
C
NCA
CM,H,Casi
Q M
C
As 5+ -CKD
H
C
CM,Casi
NCA
NCA
NCA NCA
CaSi
CaSi
As 5+ -PC
5
10
15
20
25
30
35
40
45
50
55
60
65
(b)
2 θ
FIGURE 21.3
XRPD.patterns.of.10.wt%.(a).As(III).and.(b).As(V).stabilized.by.Portland.cement.and.cement.
kiln.dust.aged.for.24.h..(From.Yoon,.I.H..et.al.,. J. Environ. Manag .,.91(11),.2322,.2010.)
The. functional. groups. shown. in. Table. 21.3. are. only. A-type. Fe-OH 2 . and.
Fe-OH. bound. to. a. single. structural. Fe. via. ligand. exchange. reactions..
Both. Fe-OH 2 . and. Fe-OH. exist. in. appreciable. concentrations. at. pH. 4.6,.
and. Fe-OH. dominates. at. pH. 9.2.. The. surface. OH 2 . and. OH . groups. are.
bonded.in.a.bidentate.edge-sharing.complex.(Fe-O 2 -As).or.corner-sharing.
complex.((Fe-O) 2 -As).
Iron.can.also.form.insoluble.iron-arsenic.compounds,.such.as.FeAsO 4 ..The.
amorphous. ferric. arsenate. (FeAsO 4 ). and. scorodite. are. an. insoluble. As(V).
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