. SEM images of the Biochar@Kaolin and Biochar@Bentonite before and after the reaction with Cr(VI)
. TEM images of the Biochar@Kaolin and Biochar@Bentonite before and after the reaction with Cr(VI)
. EDS spectra of the Biochar@Kaolin and Biochar@Bentonite before and after the reaction with Cr(VI)
. XRD patterns of Biochar, Biochar@Kaolin and Biochar@Bentonite
. FT-IR spectra of Biochar, Kaolin, Bentonite, Biochar@Kaolin and Biochar@Bentonite
. XPS spectra of Biochar@Kaolin (a) and Biochar@Bentonite (b)
. Effect of pH on the removal of Cr (VI) by the Biochar@Kaolin (a) and Biochar@Bentonite (b)
. Effect of SO42- on the removal of Cr (VI) by the Biochar@Kaolin (a) and Biochar@Bentonite (b)
. Adsorption data and modeling for Cr(VI) ions removal by Biochar, Biochar@Kaolin and Biochar@Bentonite, respectively
Sample | BET specific surface area/(m2·g-1) | Average pore width/nm |
---|
Biochar | 2.79 | 39.37 | Biochar@Kaolin | 6.15 | 83.41 | Biochar@Bentonite | 3.08 | 56.18 |
|
Table 1. Characterizations of Biochar, Biochar@Kaolin and Biochar@Bentonite
Sample | Pseudo-first-order | Pseudo-second-order |
---|
qe/(mg·g-1) | k1/min-1 | R2 | qe/(mg·g-1) | K2/(g·mg-1·min-1) | R2 |
---|
Biochar | 6.54 | 0.056 | 0.967 | 7.80 | 0.063 | 0.990 | Biochar@Kaolin | 7.07 | 0.092 | 0.947 | 8.91 | 0.122 | 0.986 | Biochar@Bentonite | 7.70 | 0.048 | 0.971 | 9.41 | 0.052 | 0.991 |
|
Table 2. Pseudo-first order kinetic and pseudo-second order kinetic parameters of Cr(VI) ions removal by Biochar, Biochar@Kaolin and Biochar@Bentonite
T/℃ | Sample | Langmuir adsorption model | Freundlich adsorption model |
---|
Qmax/(mg·g-1) | KL/(L·mg-1) | R2 | KF/((mg·g)-1/n) | 1/n | R2 |
---|
20 | Biochar@Kaolin | 15.58 | 0.0029 | 0.978 | 3.57 | 0.0064 | 0.995 | Biochar@Bentonite | 20.54 | 0.035 | 0.980 | 6.75 | 0.0042 | 0.903 | 30 | Biochar@Kaolin | 68.98 | 0.0063 | 0.940 | 4.55 | 0.0083 | 0.992 | Biochar@Bentonite | 23.64 | 0.058 | 0.967 | 10.53 | 0.0033 | 0.942 | 40 | Biochar@Kaolin | 76.62 | 0.13 | 0.795 | 9.61 | 0.0028 | 0.996 | Biochar@Bentonite | 27.23 | 0.28 | 0.956 | 14.82 | 0.0016 | 0.852 |
|
Table 3. Parameters of adsorption isotherms for Cr(VI) ions removal by Biochar, Biochar@Kaolin and Biochar@Bentonite at 20, 30 and 40 ℃, respectively