incorporation. Phase transformation was assessed using X-ray diffraction (XRD),
and the efficiency of Cd incorporation was quantified through Rietveld analysis of
the obtained XRD patterns. The XRD results show that Cd can be
crystallochemically incorporated into CdSiO 3 , Cd 2 SiO 4 , Cd 3 SiO 5 , CdAl 4 O 7 , and
CdFe 2 O 4 phases. The treatment temperature greatly affected the Cd incorporation
reactions. The Cd incorporation efficiency was quantified and expressed as a transformation ratio according to the weight fractions of crystalline phases in the sintering
products. To evaluate the metal stabilization effect of the Cd detoxification process, a
series of constant-pH leaching tests was conducted. A remarkable reduction in Cd
leachability was achieved by forming different Cd-hosting crystalline products,
particularly spinel phase CdFe 2 O 4 . Overall, the efforts to stabilize Cd by sintering
with ceramic matrices suggest a promising strategy for the detoxification of Cd in
wastes.
Keywords Cadmium pollution control · Ceramic matrices · Detoxification ·
Leaching tests · Sintering · Thermal stabilization · XRD analysis
Abbreviations and Nomenclature
Al 2 O 3
Alumina
AWWA
American Water Works Association
CPLT
Constant-pH leaching test
CdAl 4 O 7 Cadmium aluminate
CdFe 2 O 4 Cadmium ferrite
CdO
Cadmium oxide
CdSiO 3
Mono-cadmium silicate
Cd 2 SiO 4 Di-cadmium silicate
Cd 3 SiO 5 Tri-cadmium silicate
d
The spacing between the lattice planes of the corresponding phase
EPA
US Environmental Protection Agency
G
Gibbs free energy
ICDD
International Centre for Diffraction Data
ICP-OES Inductively coupled plasma optical emission spectrometry
MSW
Municipal solid waste
MSWI
Municipal solid waste incineration
MW
Molecular weight
PDF
Powder Diffraction File
QXRD
Quantitative X-ray diffraction
S
Entropy
SiO 2
Silicon oxide
SPLP
Synthetic precipitation leaching procedure
T
Temperature
TCLP
Toxicity characteristic leaching procedure
TR
Transformation ratio
300
M. Su et al.