Figure 1.
Structure of graphene oxide (a), Structure of tetracycline and pKa values (b).
Figure 2.
FTIR spectra of free TC, free GO and TC after adsorption on GO (GO-TC).
Figure 3.
The UV–Vis absorption spectra of free TC, free GO and TC after adsorption on GO (GO-TC).
Figure 4.
Effect of pH on the adsorption efficiency of TC (10.0–100.0 mg/L) on GO (20.0 mg/L); Temp. 25±0.1.
Figure 5.
The pseudo-first-order (a) and the pseudo-second-order (b) kinetics model for adsorption of tetracycline on GO suspension (20.0 mg/L), pH = 3.6, T = 298, 308, 318 K.
Table 1.
Kinetic parameters for TC adsorption on GO at different temperatures.
Figure 6.
Isotherm of TC (6.0–180.0 mg/L) adsorption on GO (20.0 mg/L) at different temperatures (298, 303, 308 K).
Table 2.
Langmuir, Freundlich and D–R constants and correlation coefficients of TC adsorption on GO at different temperatures.
Table 3.
Thermodynamic parameters for the adsorption of TC on GO.
Figure 7.
CV curve of tetracycline (1 mM, in phosphate buffer solution, 0.1 M, pH = 7) at 50 mV/s (a); CV curve of tetracycline (1 mM) at different scan rates: (from Bottom to up) 25, 50, 75, 100, 150, 200, 250, 300, 350, 400 mV/s (b); Observed dependence of peak current on the scan rate (c); Plot of variation of peak current with the logarithm of scan rate (d).
Figure 8.
Variation of z vs. time for C8 (triangle symbol) and amino (circle symbol).
Square symbol is z average over all TC molecules.
Figure 9.
Variation of z and x vs. time.
Figure 10.
Variation of resultant force in the z direction vs. time.