Adsorption of Acid Blue 92 Dye from Aqueous Solutions by Single-Walled Carbon Nanotubes: Isothermal, Kinetic, and Thermodynamic Studies

The aim of this study was to investigate the adsorption of Acid Blue 92 (AB92) dye onto single-walled carbon nanotubes (SWCNTs). The adsorbent was characterised by SEM, TEM, FTIR, and BET. The study comprised batch experiments conducted under varying conditions of dosage (0.01-0.2 g/L), time (10-180 min), pH (3-11), and dye initial concentration (10-200 mg/L). The optimum removal efficiency of 99.4% was achieved for AB92 at an adsorbent dosage of 0.12 g/L, dye initial concentration of 10 mg/L, pH of 3, and contact time of 75 min. The adsorption was best-fit to the pseudo-second order kinetics and Langmuir isotherm models. The monolayer adsorption capacity (q(m)) was 86.91 mg/g at 333 K. The activation energy of the system was 16.62 kJ/mol. Thermodynamics analysis revealed that the process was spontaneous ( increment G(0) was between -12.73 and -16.08 kJ/mol) and endothermic ( increment H-0 = 2.51 kJ/mol). The positive increment S-0 value (0.055 kJ/mol K) also suggests the affinity of the SWCNTs adsorbent for AB92. The mechanism of AB92 dye uptake by SWCNTs was majorly by hydrogen bonds, dipole-induced dipole bonds, London dispersion interactions, pi-pi acceptor-donor interactions, and the hydrophobic effect. The results reveal that SWCNTs is an effective adsorbent for AB92 removal from industrial effluents and wastewater.

Automated summary

This study investigated the adsorption of Acid Blue 92 dye onto single-walled carbon nanotubes. The optimum removal efficiency of 99.4% was achieved under specific conditions, with the adsorption following pseudo-second order kinetics and Langmuir isotherm models. Thermodynamic analysis indicated that the process was spontaneous and endothermic, with the adsorption mechanism primarily involving various bonding interactions and the hydrophobic effect. The results suggest that SWCNTs are effective adsorbents for removing AB92 from industrial effluents and wastewater.