Immobilization of cadmium in simulated contaminated soils using thermal-activated serpentine

Figures & data

Table 1. Physical and chemical properties of the tested soil.

pH	cation exchange capacity (cmol·kg^−1)	organic matter (g·kg^−1)	available nitrogen (mg·kg^−1)	available phosphorus (mg·kg^−1)	available potassium (mg·kg^−1)	total cadmium (mg·kg^−1)
7.19	12.81	17.47	86.92	7.83	82.93	0.23

Table 2. The composition and content of natural serpentine.

Composition	SiO2	MgO	CaO	Al2O3	Fe2O3
Content (wt. %)	51.00	47.32	0.92	0.38	0.38

Table 3. Changes of pH in Cd contaminated soil with different serpentine treatments and results of ANOVA.

Sample		Soil pH
		15 days	30 days	60 days
CK		7.14 ± 0.13 h	7.30 ± 0.05 g	7.29 ± 0.10e
S0-1		7.85 ± 0.03 g	7.76 ± 0.04ef	7.71 ± 0.06 cd
S0-3		7.86 ± 0.02 g	7.79 ± 0.09def	7.77 ± 0.06bcd
S0-5		7.88 ± 0.09 g	7.82 ± 0.04bcdef	7.81 ± 0.03bcd
S350-1		7.85 ± 0.02 g	7.75 ± 0.02 f	7.70 ± 0.06d
S350-3		7.90 ± 0.07 fg	7.81 ± 0.01def	7.8 ± 0.04bcd
S350-5		7.95 ± 0.14efg	7.81 ± 0.05 cdef	7.81 ± 0.06bcd
S550-1		7.98 ± 0.07defg	7.89 ± 0.03abcdef	7.82 ± 0.05bcd
S550-3		8.08 ± 0.02 cdef	7.93 ± 0.07abcde	7.86 ± 0.06abcd
S550-5		8.14 ± 0.02bcde	7.98 ± 0.04ab	7.92 ± 0.06ab
S700-1		8.27 ± 0.03abc	7.96 ± 0.07abcd	7.90 ± 0.04ab
S700-3		8.29 ± 0.05ab	7.98 ± 0.11abc	7.94 ± 0.03ab
S700-5		8.34 ± 0.08a	8.04 ± 0.07a	8.01 ± 0.07a
S850-1		8.14 ± 0.02bcde	7.92 ± 0.05abcde	7.86 ± 0.06abcd
S850-3		8.15 ± 0.01abcd	7.93 ± 0.05abcd	7.88 ± 0.06abc
S850-5		8.16 ± 0.03abcd	7.95 ± 0.03abcd	7.90 ± 0.05ab
SS	between groups	3.607	1.322	1.144
	within groups	0.134	0.100	0.108
	total	3.741	1.422	1.252
DF	between groups	15	15	15
	within groups	32	32	32
	total	47	47	47
MS	between groups	0.240	0.088	0.076
	within groups	0.004	0.003	0.003
F		57.456	28.160	22.617
Sig.		0.000	0.000	0.000

Data are means ± SD (n = 3). Means with different letters in the same column are significantly different from each other (P < 0.05) according to the Tukey test.

The results of ANOVA: SS = sum of squares, DF = degrees of freedom, MS = mean square.

Table 4. Effects of different serpentines on TCLP-Cd content in soil and results of ANOVA.

sample		TCLP-Cd (mg·kg^−1)
		15 days	30 days	60 days
CK		6.63 ± 0.32a	6.61 ± 0.32a	6.51 ± 0.28a
S0-1		5.99 ± 0.20b	5.52 ± 0.22b	5.17 ± 0.38b
S0-3		5.76 ± 0.16bcd	5.31 ± 0.06bc	4.95 ± 0.23bcd
S0-5		5.58 ± 0.25bcde	5.18 ± 0.13bcd	4.55 ± 0.15def
S350-1		5.90 ± 0.16bc	5.39 ± 0.15bc	5.12 ± 0.05b
S350-3		5.73 ± 0.14bcd	5.29 ± 0.11bc	4.91 ± 0.10bcd
S350-5		5.54 ± 0.08cdef	5.11 ± 0.11bcd	4.49 ± 0.08def
S550-1		5.88 ± 0.10bcd	5.36 ± 0.11bc	5.09 ± 0.05bc
S550-3		5.59 ± 0.09bcde	5.22 ± 0.18bc	4.88 ± 0.07bcde
S550-5		5.24 ± 0.04ef	4.88 ± 0.16cde	4.42 ± 0.09efg
S700-1		5.69 ± 0.05bcd	5.12 ± 0.41bcd	4.35 ± 0.10fg
S700-3		5.20 ± 0.09efg	4.48 ± 0.23ef	3.98 ± 0.06 g
S700-5		4.88 ± 0.08g	4.09 ± 0.07f	3.40 ± 0.16 h
S850-1		5.77 ± 0.13bcd	5.27 ± 0.07bc	4.95 ± 0.13bcd
S850-3		5.44 ± 0.10def	4.99 ± 0.08bcde	4.60 ± 0.15cdef
S850-5		5.13 ± 0.02fg	4.65 ± 0.11de	4.23 ± 0.08fg
SS	between groups	7.584	13.082	20.179
	within groups	0.686	1.077	0.835
	total	8.271	14.159	21.014
DF	between groups	15	15	15
	within groups	32	32	32
	total	47	47	47
MS	between groups	0.506	0.872	1.345
	within groups	0.021	0.034	0.026
F		23.571	25.900	51.566
Sig.		0.000	0.000	0.000

Data are means ± SD (n = 3). Means with different letters in the same column are significantly different from each other (P < 0.05) according to the Tukey test.

The results of ANOVA: SS = sum of squares, DF = degrees of freedom, MS = mean square.

Table 5. Regression analysis on TCLP-Cd in soil and soil pH in different periods.

Incubation time/day	Equation of linear regression	R
15	Y = −1.155pH+14.851	−0.926**
30	Y = −2.544pH+25.127	−0.913**
60	Y = −3.268pH+30.321	−0.925**

**P < 0.01.

Table 6. The changes of exchangeable form of Cd content in soil after the application of different serpentines and results of ANOVA.

Sample		Exchangeable form of Cd (mg·kg^−1)
		15 days	30 days	60 days
CK		6.33 ± 0.08a	6.30 ± 0.05a	6.27 ± 0.06a
S0-1		5.72 ± 0.03b	5.36 ± 0.03b	5.03 ± 0.09b
S0-3		5.43 ± 0.06 cd	5.12 ± 0.02 cd	4.72 ± 0.04d
S0-5		5.25 ± 0.04def	4.92 ± 0.08ef	4.40 ± 0.02f
S350-1		5.55 ± 0.06bc	5.24 ± 0.05bc	4.96 ± 0.07bc
S350-3		5.30 ± 0.10def	5.00 ± 0.04de	4.64 ± 0.07de
S350-5		5.20 ± 0.05efg	4.81 ± 0.07fg	4.38 ± 0.03fg
S550-1		5.40 ± 0.13cde	5.02 ± 0.03de	4.73 ± 0.05d
S550-3		5.02 ± 0.04gh	4.73 ± 0.03 g	4.45 ± 0.09 f
S550-5		4.77 ± 0.06i	4.50 ± 0.03 h	4.17 ± 0.04 h
S700-1		4.66 ± 0.12ij	4.48 ± 0.09 h	4.32 ± 0.06fgh
S700-3		4.45 ± 0.06 j	4.16 ± 0.05i	3.77 ± 0.08i
S700-5		4.19 ± 0.06 k	3.83 ± 0.03 j	3.27 ± 0.05 j
S850-1		5.45 ± 0.08cd	5.11 ± 0.03 cd	4.82 ± 0.09 cd
S850-3		5.17 ± 0.04fg	4.88 ± 0.07ef	4.50 ± 0.05ef
S850-5		4.86 ± 0.02 hi	4.54 ± 0.05 h	4.21 ± 0.01 gh
SS	between groups	12.143	13.765	18.394
	within groups	0.164	0.084	0.120
	total	12.307	13.849	18.514
DF	between groups	15	15	15
	within groups	32	32	32
	total	47	47	47
MS	between groups	0.810	0.918	1.226
	within groups	0.005	0.003	0.004
F		158.239	349.446	328.066
Sig.		0.000	0.000	0.000

Data are means ± SD (n = 3). Means with different letters in the same column are significantly different from each other (P < 0.05) according to the Tukey test.

The results of ANOVA: SS = sum of squares, DF = degrees of freedom, MS = mean square.

Table 7. The changes of carbonate form of Cd content in soil after the application of different serpentines and results of ANOVA.

Sample		Carbonate form of Cd (mg·kg^−1)
		15 days	30 days	60 days
CK		0.71 ± 0.05f	0.72 ± 0.03j	0.73 ± 0.03h
S0-1		0.86 ± 0.03e	0.91 ± 0.01i	0.97 ± 0.01g
S0-3		0.94 ± 0.03de	1.00 ± 0.01gh	1.07 ± 0.03efg
S0-5		0.98 ± 0.01 cd	1.08 ± 0.02ef	1.19 ± 0.02cd
S350-1		0.90 ± 0.06de	0.94 ± 0.02hi	0.98 ± 0.02g
S350-3		0.95 ± 0.05de	1.05 ± 0.02fg	1.12 ± 0.06def
S350-5		1.00 ± 0.01cd	1.14 ± 0.02cde	1.20 ± 0.01bcd
S550-1		0.94 ± 0.06de	0.99 ± 0.02gh	1.03 ± 0.05fg
S550-3		1.08 ± 0.05bc	1.11 ± 0.01def	1.12 ± 0.04cdef
S550-5		1.12 ± 0.01b	1.16 ± 0.01bcd	1.21 ± 0.02bcd
S700-1		1.13 ± 0.03b	1.19 ± 0.01bc	1.22 ± 0.01bc
S700-3		1.19 ± 0.01ab	1.22 ± 0.04ab	1.30 ± 0.08ab
S700-5		1.25 ± 0.00a	1.27 ± 0.03a	1.39 ± 0.03a
S850-1		0.93 ± 0.05de	0.97 ± 0.02hi	0.99 ± 0.01g
S850-3		1.00 ± 0.03cd	1.05 ± 0.04fg	1.15 ± 0.00cde
S850-5		1.12 ± 0.01b	1.11 ± 0.01def	1.21 ± 0.01bcd
SS	between groups	0.841	0.849	1.093
	within groups	0.043	0.016	0.038
	total	0.884	0.864	1.131
DF	between groups	15	15	15
	within groups	32	32	32
	total	47	47	47
MS	between groups	0.056	0.057	0.073
	within groups	0.001	0.000	0.001
F		41.685	115.889	61.692
Sig.		0.000	0.000	0.000

Data are means ± SD (n = 3). Means with different letters in the same column are significantly different from each other (P < 0.05) according to the Tukey test.

The results of ANOVA: SS = sum of squares, DF = degrees of freedom, MS = mean square.

Table 8. The changes of Fe-Mn oxide form of Cd content in soil after the application of different serpentines and results of ANOVA.

Sample		Fe-Mn oxide form of Cd (mg·kg^−1)
		15 days	30 days	60 days
CK		0.73 ± 0.01 h	0.74 ± 0.01i	0.74 ± 0.01 h
S0-1		0.89 ± 0.01g	0.96 ± 0.02h	1.07 ± 0.02 g
S0-3		0.99 ± 0.02efg	1.06 ± 0.03defg	1.17 ± 0.01ef
S0-5		1.05 ± 0.05def	1.13 ± 0.04cdef	1.23 ± 0.02cde
S350-1		0.96 ± 0.02fg	0.99 ± 0.02gh	1.09 ± 0.02g
S350-3		1.06 ± 0.05 cdef	1.08 ± 0.05defg	1.18 ± 0.02cdef
S350-5		1.07 ± 0.04cde	1.16 ± 0.04bcd	1.24 ± 0.01 cde
S550-1		0.98 ± 0.01efg	1.05 ± 0.04efgh	1.12 ± 0.01fg
S550-3		1.12 ± 0.05bcd	1.14 ± 0.03 cde	1.19 ± 0.04cde
S550-5		1.20 ± 0.01ab	1.22 ± 0.05abc	1.25 ± 0.05c
S700-1		1.13 ± 0.02bcd	1.19 ± 0.01abc	1.24 ± 0.02cd
S700-3		1.21 ± 0.00ab	1.23 ± 0.01ab	1.34 ± 0.03b
S700-5		1.28 ± 0.01a	1.28 ± 0.03a	1.43 ± 0.02a
S850-1		0.97 ± 0.07efg	1.04 ± 0.01fgh	1.11 ± 0.01fg
S850-3		1.07 ± 0.07 cde	1.12 ± 0.01 cdef	1.18 ± 0.02def
S850-5		1.16 ± 0.01bc	1.18 ± 0.04bc	1.25 ± 0.01c
SS	between groups	0.831	0.774	0.971
	within groups	0.041	0.032	0.015
	total	0.872	0.806	0.987
DF	between groups	15	15	15
	within groups	32	32	32
	total	47	47	47
MS	between groups	0.055	0.052	0.065
	within groups	0.001	0.001	0.000
F		43.246	51.004	134.800
Sig.		0.000	0.000	0.000

Data are means ± SD (n = 3). Means with different letters in the same column are significantly different from each other (P < 0.05) according to the Tukey test.

The results of ANOVA: SS = sum of squares, DF = degrees of freedom, MS = mean square.

Table 9. The changes of organic form of Cd content in soil after the application of different serpentines and results of ANOVA.

Sample		Organic form of Cd (mg·kg^−1)
		15 days	30 days	60 days
CK		0.065 ± 0.010e	0.066 ± 0.009e	0.066 ± 0.008d
S0-1		0.084 ± 0.004d	0.090 ± 0.007d	0.096 ± 0.002 c
S0-3		0.083 ± 0.009d	0.098 ± 0.004bcd	0.099 ± 0.006bc
S0-5		0.092 ± 0.005bcd	0.099 ± 0.004bcd	0.102 ± 0.003abc
S350-1		0.089 ± 0.001 cd	0.094 ± 0.005 cd	0.101 ± 0.002abc
S350-3		0.092 ± 0.004bcd	0.099 ± 0.003bcd	0.103 ± 0.003abc
S350-5		0.094 ± 0.003bcd	0.100 ± 0.003abcd	0.103 ± 0.002abc
S550-1		0.090 ± 0.000bcd	0.099 ± 0.000bcd	0.104 ± 0.002abc
S550-3		0.092 ± 0.003bcd	0.103 ± 0.003abc	0.105 ± 0.002abc
S550-5		0.094 ± 0.004bcd	0.103 ± 0.003abc	0.106 ± 0.003ab
S700-1		0.101 ± 0.003abc	0.104 ± 0.004abc	0.107 ± 0.003ab
S700-3		0.103 ± 0.002ab	0.108 ± 0.002ab	0.109 ± 0.003ab
S700-5		0.109 ± 0.002a	0.112 ± 0.003a	0.111 ± 0.003a
S850-1		0.09 ± 0.002bcd	0.095 ± 0.004 cd	0.103 ± 0.001abc
S850-3		0.096 ± 0.006abcd	0.102 ± 0.003abc	0.104 ± 0.003abc
S850-5		0.097 ± 0.004abcd	0.103 ± 0.001abc	0.104 ± 0.002abc
SS	between groups	0.004	0.005	0.005
	within groups	0.001	0.001	0.000
	total	0.005	0.006	0.005
DF	between groups	15	15	15
	within groups	32	32	32
	total	47	47	47
MS	between groups	0.000	0.000	0.000
	within groups	0.000	0.000	0.000
F		13.331	19.504	27.146
Sig.		0.000	0.000	0.000

Data are means ± SD (n = 3). Means with different letters in the same column are significantly different from each other (P < 0.05) according to the Tukey test.

The results of ANOVA: SS = sum of squares, DF = degrees of freedom, MS = mean square.

Table 10. The changes of residual form of Cd content in soil after the application of different serpentines and results of ANOVA.

Sample		Residual form of Cd (mg·kg^−1)
		15 days	30 days	60 days
CK		0.40 ± 0.03i	0.41 ± 0.03 h	0.42 ± 0.02 j
S0-1		0.68 ± 0.03 h	0.91 ± 0.01g	1.07 ± 0.06i
S0-3		0.78 ± 0.01fgh	0.95 ± 0.01fg	1.17 ± 0.00ghi
S0-5		0.86 ± 0.02efg	1.02 ± 0.03fg	1.31 ± 0.03efg
S350-1		0.73 ± 0.02gh	0.96 ± 0.02fg	1.10 ± 0.04hi
S350-3		0.83 ± 0.01efg	1.00 ± 0.01fg	1.20 ± 0.01fghi
S350-5		0.87 ± 0.03def	1.03 ± 0.02fg	1.32 ± 0.03defg
S550-1		0.81 ± 0.07efgh	1.07 ± 0.02ef	1.24 ± 0.01efgh
S550-3		0.93 ± 0.03cde	1.15 ± 0.01de	1.37 ± 0.06cde
S550-5		1.06 ± 0.05c	1.24 ± 0.03cd	1.50 ± 0.07c
S700-1		1.21 ± 0.08b	1.26 ± 0.07 cd	1.34 ± 0.06def
S700-3		1.28 ± 0.07b	1.51 ± 0.06b	1.72 ± 0.04b
S700-5		1.41 ± 0.07a	1.74 ± 0.07a	2.03 ± 0.07a
S850-1		0.80 ± 0.04efgh	1.02 ± 0.03fg	1.21 ± 0.10fghi
S850-3		0.89 ± 0.04def	1.07 ± 0.05ef	1.30 ± 0.07efg
S850-5		1.00 ± 0.01 cd	1.29 ± 0.09 c	1.46 ± 0.01cd
SS	between groups	2.716	3.718	5.085
	within groups	0.061	0.057	0.081
	total	2.777	3.775	5.166
DF	between groups	15	15	15
	within groups	32	32	32
	total	47	47	47
MS	between groups	0.181	0.248	0.339
	within groups	0.002	0.002	0.003
F		94.962	139.969	133.330
Sig.		0.000	0.000	0.000

Data are means ± SD (n = 3). Means with different letters in the same column are significantly different from each other (P < 0.05) according to the Tukey test.

The results of ANOVA: SS = sum of squares, DF = degrees of freedom, MS = mean square.

Figure 1. Distribution of various Cd forms after the application of different serpentines (incubation time 60 days).

Table 11. Relationship between TCLP-Cd in soil and surface area of serpentine.

Sample	S0	S350	S550	S700	S850
BET surface area^a/m^2 g^−1	6.1	6.2	6.7	13.7	12.0
TCLP-Cd**/mg kg^−1	4.55	4.49	4.42	3.40	4.23

^aReferring to the result reported by Cao et al. (2017).

^bThe contents of TCLP-Cd in soil treated by serpentine with 5% for 60 days

Cao, C.-Y., C.-H. Liang, Y. Yin, and L.-Y. Du. 2017. “Thermal Activation of Serpentine for Adsorption of Cadmium.” Journal of Hazardous Materials 329: 222–229. doi:10.1016/j.jhazmat.2017.01.042.

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