Magnetic multi-walled carbon nanotubes-loaded alginate for treatment of industrial dye manufacturing effluent: adsorption modelling and process optimisation by central composite face-central design

ABSTRACT

In the present study, dye(ADMI, American Dye Manufacturers’ Institute) removal from raw textile wastewater was investigated by magnetic multi-walled carbon nanotubes-loaded alginate (CNT-Alg-Fe₃O₄). The effect of key factors i.e., pH, adsorbent dose and contact time in treatment process was modelled and optimised using response surface methodology-based central composite face-centred design (RSM-CCF). Adsorbents were characterised using Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating-sample magnetometer (VSM), and energy-dispersive X-ray spectroscopy (EDS).Low value of p (7.9714e-13) and RSD (1.121) parameters, along with coefficient of determination >0.953 implied that the developed model well-fitted with experimental data. Under the optimised conditions, including pH of3, CNT-Alg-Fe₃O₄ dose of10 g L-1, and contact time of85.55 min, removal efficiency and ADMI adsorption capacity were obtained as 98.43% and 138.97ADMI/g, respectively. Fitting of data with the Langmuir isotherm (R² = 1, X² = 0.012) and Pseudo-second-order kinetics (R² = 0.993, X² = 0.015) showed that adsorption process is monolayer and chemical in nature. ΔH°> 0, ΔS°>0, and ∆G°< 0 indicated that dye removal was spontaneous and endothermic in nature. Reuse of the adsorbent in 10 consecutive experiments also showed that removal efficiency was reduced by about 11.94%.Adsorption mechanism can be explained by the presence of a large number of negatively charged carboxyl groups and hydroxyl groups on surface of CNT-Alg-Fe₃O₄, which could react with colour molecules through electrostatic interactions and π-π dispersive interactions.

KEYWORDS:

• ADMI adsorption
• magnetic carbon nanotubes-loaded alginate
• textile wastewater
• RSM-CCF
• modelling and Optimisation

Acknowledgments

The present study was adapted from the PhD thesis written by Ali Azari at the Tehran University of Medical Sciences (Tehran, Iran). The authors would like to gratefully acknowledge the financial support provided by the Tehran University of Medical Sciences [Grant No. 97-03-27-39476].

Disclosure statement

The authors declare that them have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This work was supported by the Pharmaceutical Sciences Research Center, Tehran University of Medical Sciences [97-03-27-39476].