due to its simplicity, improved reproducibility, and shorter time requirements
[123, 124]. It can be used to compare the dissolution or leaching behavior of test
samples. The test is performed at a constant pH and no buffer solution is involved.
Adding buffer solutions is a facile method of controlling the mobility of metals in the
leaching system. However, the compounds in buffer solutions may form complexes
with the metals, thus influencing the leaching performance of the tested sample
[125]. Therefore, the CPLT without buffer solutions can rapidly and precisely assess
the leaching performance of the products of a well-controlled thermal treatment
scheme.
2 Experimental Methods
2.1 Materials and Chemicals
Cadmium oxide (CdO) was used to simulate the Cd source in the waste streams.
Silica fumes (amorphous SiO 2 ), γ-Al 2 O 3 , α-Fe 2 O 3 , and Fe 3 O 4 were selected as the
ceramic matrices for Cd incorporation. γ-Al 2 O 3 was prepared via thermally treating
alumina powder (Pural SB (Sasol)) at 650
C for 3 h. Other ceramic matrices were
used as received without further purification.
2.2 Cadmium Incorporation
To examine the ability of ceramic matrices to incorporate Cd, CdO powder was
individually mixed with the ceramic matrices at desired molar ratios of Cd/Si (1/1,
2/1, and 3/1), Cd/Al (1/4), and Cd/Fe (1/2). The mixtures were well mixed in a total
weight of 10 g by mortar grinding for 30 min in the presence of absolute ethanol. The
mixtures were dried at 105
C for 24 h in a vacuum oven and then further
homogenized by mortar grinding. Subsequently, the homogenous dried powder
was pelletized into Φ 20 mm pellets at a pressure of 250 MPa. The pellets were
subjected to a well-controlled thermal treatment scheme. The sintering temperature
of the scheme was in the range of 600–1000
C and the dwelling time was set at 3 h.
2.3 Qualitative and Quantitative XRD Analysis
The fired pellets were cooled in air and then ground into powder for the XRD test.
The step-scanned diffraction data of each powder sample were recorded on a Bruker
D8 Advance X-ray powder diffractometer equipped with Cu Kα 1,2 X-ray radiation
and a LynxEye detector. The 2θ scanning range was from 10
to 80
. The step size
was 0.02
and the scan speed was 0.5 per step. The phase analyses were performed
310
M. Su et al.
[123, 124]. It can be used to compare the dissolution or leaching behavior of test
samples. The test is performed at a constant pH and no buffer solution is involved.
Adding buffer solutions is a facile method of controlling the mobility of metals in the
leaching system. However, the compounds in buffer solutions may form complexes
with the metals, thus influencing the leaching performance of the tested sample
[125]. Therefore, the CPLT without buffer solutions can rapidly and precisely assess
the leaching performance of the products of a well-controlled thermal treatment
scheme.
2 Experimental Methods
2.1 Materials and Chemicals
Cadmium oxide (CdO) was used to simulate the Cd source in the waste streams.
Silica fumes (amorphous SiO 2 ), γ-Al 2 O 3 , α-Fe 2 O 3 , and Fe 3 O 4 were selected as the
ceramic matrices for Cd incorporation. γ-Al 2 O 3 was prepared via thermally treating
alumina powder (Pural SB (Sasol)) at 650
C for 3 h. Other ceramic matrices were
used as received without further purification.
2.2 Cadmium Incorporation
To examine the ability of ceramic matrices to incorporate Cd, CdO powder was
individually mixed with the ceramic matrices at desired molar ratios of Cd/Si (1/1,
2/1, and 3/1), Cd/Al (1/4), and Cd/Fe (1/2). The mixtures were well mixed in a total
weight of 10 g by mortar grinding for 30 min in the presence of absolute ethanol. The
mixtures were dried at 105
C for 24 h in a vacuum oven and then further
homogenized by mortar grinding. Subsequently, the homogenous dried powder
was pelletized into Φ 20 mm pellets at a pressure of 250 MPa. The pellets were
subjected to a well-controlled thermal treatment scheme. The sintering temperature
of the scheme was in the range of 600–1000
C and the dwelling time was set at 3 h.
2.3 Qualitative and Quantitative XRD Analysis
The fired pellets were cooled in air and then ground into powder for the XRD test.
The step-scanned diffraction data of each powder sample were recorded on a Bruker
D8 Advance X-ray powder diffractometer equipped with Cu Kα 1,2 X-ray radiation
and a LynxEye detector. The 2θ scanning range was from 10
to 80
. The step size
was 0.02
and the scan speed was 0.5 per step. The phase analyses were performed
310
M. Su et al.