The UV–Vis absorption spectra of free TC, free GO and TC after adsorption on GO (GO-TC).

<p>The UV–Vis absorption spectra of free TC, free GO and TC after adsorption on GO (GO-TC).</p

Langmuir, Freundlich and D–R constants and correlation coefficients of TC adsorption on GO at different temperatures.

*<p>Dubinin–Radushkevich.</p

FTIR spectra of free TC, free GO and TC after adsorption on GO (GO-TC).

<p>FTIR spectra of free TC, free GO and TC after adsorption on GO (GO-TC).</p

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.

<p>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.</p

Structure of graphene oxide (a), Structure of tetracycline and pKa values (b).

<p>Structure of graphene oxide (a), Structure of tetracycline and pKa values (b).</p

Variation of resultant force in the z direction <i>vs.</i> time.

<p>Variation of resultant force in the z direction <i>vs.</i> time.</p

Variation of z and x <i>vs</i>. time.

<p>Variation of z and x <i>vs</i>. time.</p

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).

<p>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).</p

Isotherm of TC (6.0–180.0 mg/L) adsorption on GO (20.0 mg/L) at different temperatures (298, 303, 308 K).

<p>Isotherm of TC (6.0–180.0 mg/L) adsorption on GO (20.0 mg/L) at different temperatures (298, 303, 308 K).</p

Kinetic parameters for TC adsorption on GO at different temperatures.

<p>Kinetic parameters for TC adsorption on GO at different temperatures.</p